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Drying of Garlic Slices ( Allium Sativum L.) and its Effect on Thiosulfinates, Total Phenolic Compounds and Antioxidant Activity During Infrared Drying
Journal of Food Processing and Preservation
Abstract
This study was conducted to evaluate moisture transfer and changes of thiosulfinates, total phenolic compounds and antioxidant activity of garlic slices during infrared drying at temperatures from 50 to 80C and powers from 675 to 2,025 W. Drying time was significantly shortened with increasing infrared drying temperature. Thiosulfinates showed no significant changes versus moisture content during the whole drying period at 50, 60 and 70C, while a notable degradation of thiosulfinates was observed at 80C. Total phenolic compounds in garlic slices all rapidly decreased versus moisture content initially at all investigated drying conditions. Whereas the total phenolic compounds in dried garlic slices significantly enhanced with drying temperature from 50 to 80C at 1,575 W. Antioxidant activity increased during infrared drying, which was contradictory with the changes of total phenolic compounds and thiosulfinates. This work are useful for the processing of garlic slices by infrared drying to obtain the optimum benefits of bioactive compounds present in this food product during drying. Infrared drying is reported as a promising method on foodstuff processing, which impinges on the material, penetrates it, and converts the infrared energy into heat. Therefore, it is more energy saving as well as reduce drying time. In this study, drying time was significantly shortened with increasing infrared drying temperature. A remarkable decrease of total phenolic compounds versus moisture content was observed during infrared drying. Meanwhile, thiosulfinates of garlic showed fluctuation over the moisture content decreased, except a notable degradation of thiosulfinates was observed at 80C. Conflicting results were found in antioxidant activity that a clear increasing trend with decreasing moisture content during infrared drying process.
... According to reports, the increase in phenolic compounds in drying conditions may be due to several reasons, and prolonging drying time and high temperature might destroy the cellular structure and further release some bound phenolic compounds (Zhou et al., 2016). ...
... Also, some phenolic compounds were produced due to the structural transformation of polyphenols during high drying temperatures (Lopez et al., 2010). On the other hand, the formation of phenolic compounds could be due to the availability of phenolic precursors through non-enzymatic interconversion (Que et al., 2008;Zhou et al., 2016). ...
... A similar result was reported byNansereko et al. (2021) that the RWD effectively increased Jackfruit's antioxidant activity.Rajoriya et al. (2021) stated that the highest level of AOA preservation was observed in bananas dried by RWD at 90°C. It may be due to the rapid moisture decreasing at higher temperatures, which minimizes the degradation of antioxidant compounds and increases the release of restricted phenolics from the cellular matrix(Hernández-Santos et al., 2016;Zhou et al., 2016). RWD and RWD+ ...
This experiment was conducted to evaluate the effects of different drying methods on drying parameters and qualitative characteristics of Dracocephalum kotschyi in a completely randomized design with three replications. Treatments included shade drying as control, sun drying, cabinet drying (CD at 50 and 60°C), refractance window drying (RWD), infrared drying (IRD) at 200 and 300 W, and combination of RWD+ IRD at 200 and 300 W. According to the results, IRD, RWD, and RWD+ IRD effectively maintained valuable secondary metabolites compared to the conventional drying methods. The maximum total phenol content (2.7 and 2.66 mg GAE/g dry weight), total flavonoid content (2.26 and 2.33 mg QE/g dry weight), antioxidant activity (79% and 78.33%), and essential oil content (0.65% and 0.76%) were obtained from plants dried by RWD and IRD. Samples dried by RWD, IRD, and RWD+ IRD had high color quality, acceptable green color, and less browning. Also, RWD and IRD methods effectively reduced microbial contamination of dried plants compared to the control and other methods. The minimum aerobic mesophiles, mold, yeast, and coliforms were observed at 3.11, 0, and 1.47 log CFU/g in IRD 300 W and 3.17, 1, and 1.30 log CFU/g in RWD. D. kotschyi dried at CD 50°C had the maximum microbial contamination. Generally, according to the obtained results, RWD and IRD methods are suggested for drying of D. kotschyi and similar herbs due to shortening the drying time, preserving and improving the quality properties of dried plants.
... Proses pengeringan meningkatkan pelepasan senyawa fenolik yang terikat pada dinding sel tumbuhan [11]. Kandungan fenolik total dan antioksidan dalam bawang yang dikeringkan mengalami peningkatan [12]. Namun seiring dengan meningkatnya suhu pengeringan akan memungkinkan terjadi kerusakan senyawa antioksidan yang terkandung dalam bawang, sehingga perlu dilakukan optimasi suhu pengeringan untuk mendapatkan hasil yang maksimal [9]. ...
... Data penelitian untuk kandungan fenolik total dan aktivitas antioksidan dianalisis menggunakan statistik parametrik yaitu One-way ANOVA dengan uji lanjut Duncan. Hasil dinyatakan sebagai rata-rata ± standar deviasi dengan tingkat signifikansi 0,05 [12]. ...
... Proses pengeringan dapat meningkatkan kandungan fenolik total bawang putih dan bawang hitam. Senyawa fenolik total pada bawang putih iris yang dikeringkan menggunakan infrared drying dengan suhu 60 o C sebesar 0,761 mg GAE/g [12]. Berbagai metode pengeringan yang berbeda menghasilkan peningkatan hingga 10 kali lipat dalam kandungan fenolik total buah apel, pepaya, dan ubi jalar kering [19]. ...
Bawang hitam merupakan produk bawang putih segar yang telah dipanaskan selama dua minggu pada suhu yang terkontrol (65-90oC). Bawang hitam memiliki warna, bau, dan rasa yang berbeda dengan bawang putih. Kadar air yang cukup tinggi dari bawang putih dan bawang hitam menyebabkan bahan pangan ini mudah membusuk. Teknik pengeringan dengan oven dapat memperpanjang umur simpan bawang tersebut. Tujuan penelitian ini yaitu mengetahui pengaruh suhu pengeringan terhadap kandungan fenolik total dan aktivitas antioksidan bawang putih bubuk dan bawang hitam bubuk. Bawang putih dan bawang hitam dikeringkan pada suhu 60, 70, 80, dan 90oC. Kandungan fenolik total ditentukan dengan reagen Folin-Ciocalteu dan aktivitas antioksidan diukur dengan metode 2,2-diphenyl-1-picryhydrazyl (DPPH). Hasil penelitian menunjukkan bahwa suhu pengeringan terbaik pada bawang putih yaitu suhu 60oC yang memiliki kandungan fenolik total 0,178 mg gallic acid equivalent (GAE)/g dan sifat antioksidan sedang dengan nilai IC50 105,01 ppm; sedangkan suhu pengeringan terbaik pada bawang hitam yaitu suhu 80oC yang memiliki kandungan fenolik total 2,957 mg gallic acid equivalent (GAE)/g dan sifat antioksidan kuat dengan nilai IC50 67,32 ppm. Kata kunci : bawang hitam, bawang putih, fenolik, antioksidan
... Garlic (Allium sativum L.), which contains abundant allicin and polyphenols, is utilized throughout the world as a flavouring agent or medicinal herb (Feng et al., 2019;Papu et al., 2014). Epidemiological studies have proved that garlic has the role of preventing cardiovascular diseases, anti-cancer, and anti-pathogenic microorganisms due to the presence of those bioactive components (Zhou et al., 2017). The high water content of fresh garlic cloves, representing more than 75% (web basis), makes garlic prone to quick germination and rotting during storage, which results in shorter shelf life and hence causes great economic losses to the sellers (Babetto, Freire, Barrozo, & Freire, 2011;Feng et al., 2020;Papu et al., 2014). ...
... The results were expressed as milligrams allicin per 100 g of the sample based on the dry weight (mg/ 100 g, dry basis). The Folin-Ciocalteu reagent method was adopted for the determination of the total phenolics content of the garlic samples (Zhou et al., 2017). The results were expressed as gallic acid equivalents (GAE, mg/g, dry basis). ...
... The contents of allicin and total phenolics of the fresh garlic were 165.43 (mg/100 g, dry basis) and 3.48 (GAE, mg/g, dry basis), respectively, which were slightly higher than those (153.00 mg/100 g, dry basis and 2.72 GAE, mg/g, dry basis, respectively) reported by Abano, Ma, & Qu (2011) and Zhou et al. (2017); this difference may be related to the different sources of garlic. In Table 1, all drying treatments led to a loss in bioactive compounds of garlic, which might be resulted from the combined effects of the time duration and temperature of drying, and Y. Feng, et al. ...
BACKGROUND
Fresh shiitake mushrooms are rich in nutrients, but have high water content, a fast metabolism after harvest, and deteriorate extremely easily. Therefore, the drying of shiitake mushrooms has become a research direction. However, the role of different drying techniques on shiitake mushroom quality is limited. Therefore, the purpose of this study was to investigate the effect of thermal and non‐thermal drying on the drying kinetics, and the physicochemical properties of the end product.
RESULTS
Results showed that shiitake mushroom treated with non‐thermal drying (vacuum freeze‐drying) had an attractive color, low shrinkage, and uniform honeycomb structure, while the drying time was the longest and not conducive to the formation of shiitake mushroom aroma. But shiitake mushroom treated with thermal drying presents an attractive fragrance. In thermal processing technology, compared with hot air convection drying (HAD), infrared hot air convection drying (IRHAD) shortens the drying time by 37.5%, and had the highest oxidation resistance, polysaccharide content and the lowest color change. Relative‐humidity drying (RHD) samples had the lowest shrinkage compared with other thermal processing technology. The five polysaccharides exhibited similar preliminary structural characteristics, but the polysaccharides obtained by IRHAD have the highest antioxidant properties.
CONCLUSION
These results showed that compared with thermal drying technology, non‐thermal drying technology is not suitable for shiitake mushroom processing. In thermal processing technology, IRHAD is a potential drying method to obtain high‐quality dried shiitake mushrooms and shiitake mushroom polysaccharide (SMP). However, it is necessary to increase the pretreatment technology to achieve the attractive appearance of non‐thermal drying technology. © 2021 Society of Chemical Industry.
... A similar impact of increased temperature on the drying of garlic was observed in the study by Calín-Sánchez et al. and Zhou et al. investigated the influence of temperature on the drying of garlic using infrared drying as the drying technique [41,42]. Additionally, the impact of the drying method on phenolic compounds has been investigated in various plant materials. ...
... Mitra et al. (2011) optimized the vacuum drying technique for black onion and determined a recommended drying temperature of 58.66 °C, resulting in the highest content of total thiosulfinates [50]. Zhou et al. found that infrared radiation drying at lower temperatures (50-70 °C) minimized thiosulfinate degradation, while higher temperatures led to a reduction in thiosulfinates due to their thermolabile nature [42]. ...
Medicinal and aromatic plants, such as wild garlic (Allium ursinum), are valuable sources of bioactive compounds in traditional and modern medicine. However, the challenges in cultivating wild garlic and its seasonality limit its availability primarily to early spring. To maintain the quality of wild garlic, effective postharvest practices are essential, considering the delicate nature of its leaves and their susceptibility to rapid decay. This study focuses on implementing eco-friendly postharvest practices to address the seasonality and perishability of wild garlic. Optimizing storage conditions and drying processes is essential for extending its shelf life and preserving bioactive components. Two postharvest approaches were evaluated, with vacuum packaging at 4 °C demonstrating the most effective preservation of sensory attributes and bioactive composition over a 9-day period. Additionally, different drying methods, including convective and vacuum drying at various temperatures, were investigated. When the best drying temperature was selected, the results revealed that convective drying is more efficient at preserving phenolic compounds in wild garlic leaves at 60 °C. Conversely, vacuum drying shows superior preservation of alliinase activity and total thiosulfinate content at 70 °C. Furthermore, this study explores the utilization of unused wild garlic, which is typically discarded as waste during storage. By employing suitable drying methods, this material can be preserved and provide a valuable source of phenolic compounds (7.17–10.12 g GAE/100 g) and thiosulfinate (9.35–12.72 mg AC/110 g) compounds for various extraction processes. Accordingly, this research presents significant implications for the integration of wild garlic into diverse industries, particularly in the fields of food and pharmaceutical sectors. The findings offer opportunities for sustainable utilization, economic benefits, and a more environmentally friendly and economically viable approach to wild garlic production and processing.
... High-temperature processing decreases their bioavailability [301,302], while high-pressure processing reduces their anticancer, antimicrobial, and antioxidative properties, decreases their enzyme alliinase activity [303] and improves their enzyme alliinase activity [304,305]. Moreover, freeze-drying and infrared-drying technologies [306] and microwave-assisted and pressurized liquid extractions have negative thermal effects. Therefore, only supercritical fluid extraction is suitable for efficient extraction among the new technologies used to replace conventional ones [307]. ...
... technologies [306] and microwave-assisted and pressurized liquid extractions have negative thermal effects. Therefore, only supercritical fluid extraction is suitable for efficient extraction among the new technologies used to replace conventional ones [307]. ...
The modern linear agricultural production system allows the production of large quantities of food for an ever-growing population. However, it leads to large quantities of agricultural waste either being disposed of or treated for the purpose of reintroduction into the production chain with a new use. Various approaches in food waste management were explored to achieve social benefits and applications. The extraction of natural bioactive molecules (such as fibers and antioxidants) through innovative technologies represents a means of obtaining value-added products and an excellent measure to reduce the environmental impact. Cosmetic, pharmaceutical, and nutraceutical industries can use natural bioactive molecules as supplements and the food industry as feed and food additives. The bioactivities of phytochemicals contained in biowaste, their potential economic impact, and analytical procedures that allow their recovery are summarized in this study. Our results showed that although the recovery of bioactive molecules represents a sustainable means of achieving both waste reduction and resource utilization, further research is needed to optimize the valuable process for industrial-scale recovery.
... Previous studies have confirmed that longer DTs and higher temperatures were associated with a loss of phenolic compounds in A. porrum vegetables [41]. However, the application of higher temperature for a shorter time may also have a beneficial effect in preserving phenolic compounds in vegetables [42,43]. An increase in drying temperature significantly reduced TPC in the GR of leek. ...
... Previous studies have confirmed that longer DTs and higher temperatures were associated with a loss of phenolic compounds in A. porrum vegetables [41]. However, the application of higher temperature for a shorter time may also have a beneficial effect in preserving phenolic compounds in vegetables [42,43]. ...
This study aimed to analyze the antioxidant activity, phenolic acid profile, color changes, and chemical composition of dried and powdered leek (Allium porrum). Leek was divided into white shaft (WH) and green shaft (GR) and subjected to drying by different methods—convection drying, vacuum drying, and freeze-drying (FD)—at a temperature of 60 °C. A sample freeze-dried at a temperature of 20 °C was used as control. Analyses of the dried leek samples revealed that GR contained a higher amount of ash, protein, fat, fiber, phenolic acids, and flavonoids, and exhibited higher antioxidant capacity compared to WH. The dominant phenolic acid in WH was p-cumaric acid followed by synapic and protocatechuic acids. GR had a several-fold higher content of phenolic acids than WH, with ferulic acid being dominant (about 85% of the total phenolic content). It was also observed that a higher drying temperature resulted in the degradation of phenolic compounds and reduced the antioxidant properties of leek shafts. Most importantly, FD under a temperature of 60 °C caused a similar degree of degradation of biologically active compounds as air drying. An increase in drying temperature was associated with a slight decrease in the lightness of GR, whereas in the case of WH no significant change in this parameter was observed.
... Zhou [13] et al., (2016) conducted to evaluate moisture transfer and changes of thiosulfates, total phenolic compounds and antioxidant activity of garlic slices during infrared drying at temperatures from 50 to 80 ºC and powers from 675 to 2,025 W. Drying time was significantly shortened with increasing infrared drying temperature. Thiosulfates showed no significant changes versus moisture content during the whole drying period at 50 ºC, 60 ºC and 70 ºC, while a notable degradation of thiosulfates was observed at 80 ºC. ...
Nature is a good friend of human. Plants are serving humanity from hundreds of the years. Herbal/ayurvedic medicines are used for the treatment of several diseases without any harm. Allium species are one of the remedial herbs with bioactive parts, that act as medicinal plant and cure diseases, their roots stems leaves and also juices are valuable for human health. Allium species like (Allium cepa, Allium sativum, Zingiber officinale) are studied for the treatment of cancer, cardiovascular diseases, inflammation, reducing blood sugar, baldness, gastric ulcer, colic diseases, oxidative damage, etc. These species are evaluated for their total phenolics, flavonoids, antioxidant activity, hepatoprotective and microbial study. Total phenolic content was examined spectrophotometrically with the Folin-Ciocalteu phenol reagent and total antioxidant activity were studied by the ferric reducing antioxidant power (FRAP) and diphenyl picryl hydrazyl (DPPH) methods. Watery and alcoholic concentrates in Pbs subjected to an antibacterial activity test using the agar well diffusion procedure against various contagious pathogenic microorganisms. HPLC and LC-MS/MS demonstrated the nearness of Gallic corrosive, ferulic corrosive, protocatechuic corrosive, kaempferol, curcumin and quercetin content can possibly contribute as a dietary supplement for controlling hyperglycemia, treatment of alopecia areata and oxidative anxiety connected diabetes complexities. The biological activities, chemical characteristics and used in pharmaceutics are well studied. Some of its major chemical components reported are volatile oils, steroids, diterpinoids, flavonoids and phenolic compounds.
... Lu et al. [19] also evaluated the effect of thermal treatment on the deterioration of polysaccharides during processing of black garlic and revealed a considerable rise in the reducing sugar concentration, indicating the breakdown of polysaccharides into simpler sugar like glucose and fructose. [40] where with increase in drying temperature from 50 to 80 °C, TPC increased from 57 to 147 mg/g in garlic powder. This was attributed to higher temperature leading to breakdown of cell wall and releasing the bound phenolics from the plant's insoluble section [10,11]. ...
The work aimed to evaluate the effect of various pre-treatments and drying methods in order to maximize the quality and retention of bioactive compounds in garlic powder. Fumigation was the pretreatment that reduced residual enzymatic activity the most while maintaining the powder’s colour characteristics. Therefore, fumigation was used as a pre-treatment before subjecting garlic to various drying methods including tray drying, solar drying, microwave drying and hybrid drying methods for comparative analysis of garlic powder produced. Microwave dried powder at 180W achieved highest retention of allicin content, total phenols, total flavonoid content and antioxidant activity while tray drying offered superior colour preservation. In addition to reducing drying time and exhibiting a modest degree of colour preservation hybrid drying methods including ultrasound + tray drying (US + TD) and microwave + tray drying (MW + TD) showed a notable retention of bioactive. Remarkable stability of bioactive compounds was also demonstrated by microwave + convective drying (MW + CNV) and preheat + convection (PH + CNV), but with poor colour quality. However, because of prolonged drying time and non-uniform temperature, solar dried powder showed least amount of phytochemical while maintain colour values. Consequently, results indicate that with increase in temperature and microwave power there was increase in rehydration ratio, dehydration ratio, tapped density and bulk density. Presence of aldehyde, phenols, alcohols, sulfoxides, alkenes and nitro compounds in garlic powder was confirmed with Fourier transform infrared spectroscopy (FTIR). Overall microwave and hybrid drying methods are suggested for producing high quality powder while tray drying provides a more commercially feasible approach that retains enough bioactive with easy scalability for large scale food processing and pharmaceutical.
... This versatile herb has been utilized worldwide as both a medicinal herb and a flavouring agent (Feng et al., 2019;Papu et al., 2014). Extensive epidemiological studies have demonstrated the numerous health benefits of garlic, including its role in preventing cardiovascular diseases, its anti-cancer properties, and its ability to combat pathogenic microorganisms, thanks to the presence of these bioactive components (Zhou et al., 2017). ...
This comprehensive study delves into a myriad of innovative techniques for extending the shelf life of minimally processed garlic cloves (Allium Sativum L.). Our goal is to uncover a convenient and effortless preservation method that ensures the availability of ready-to-use, waste-free garlic cloves. Through an extensive review of relevant literature, we have identified the modified atmospheric packaging (MAP) method as the most suitable approach for storing peeled garlic cloves, without the need for any chemical coatings on the delectable cloves. By creating a controlled modified atmosphere consisting of optimal nitrogen (N2 %) and carbon dioxide (CO2 %) levels, MAP significantly reduces the cloves' respiration rate, thereby enhancing their shelf life and ensuring their long-lasting freshness.
... Higher drying temperatures may increase thermal flux from the drying medium, raising the temperature differential between the drying medium and the drying product and enhancing the heat transfer rate (Zeng et al., 2019). A comparable result was also reported in the optimization of the infrared drying process of pumpkin and garlic slices (Zhou et al., 2017). ...
Drying desiccated coconut is always challenging due to its sensitivity to heat, which can reduce its color quality. The main goal of this study is to optimize infrared drying (IR) efficiency without affecting the final color quality of desiccated coconut. Single-mode infrared drying was optimized using Response Surface Methodology (RSM) with a central composite rotatable design (CCRD). Using a radiation output of 600 Watts and a fixed distance of 15 cm from the emitter, a single layer of fresh shredded coconut with a wet basis of approximately 51.35±4.0% was dried to less than 3% (w.b). Drying temperature and air velocity were taken into consideration as independent parameters. The selected optimal drying conditions, with the desirability value (D = 0.812), were 61°C drying temperature and 2.2 m/s air velocity. The response of optimal values for drying time, specific energy consumption (SEC), color changes, and whiteness index were 36.826 minutes, 19.821 kWh/ kg, 3.431, and 71.762, respectively. Models for predicting these response values had R 2 values of more than 0.90. All responses were shown to be significantly impacted by drying temperature and air velocity (p<0.05), with drying temperature having a larger effect than air velocity. The optimal drying parameters were validated with a less than 2% deviation.
... In vitro and animal studies have shown that garlic can suppress many types of cancer, such as blood, bladder, stomach, breast, oral cavity, lung cancer, colorectal cancer, skin cancer, and uterine cancer [71][72][73]. Epidemiological studies have shown that garlic has a role in the prevention of cardiovascular diseases due to the presence of these bioactive components [74]. Garlic consumption may protect the brain from loss of intellectual capacity and may reduce the risk of Alzheimer's disease [75]. ...
Phytotherapy is attracting increased interest for several reasons. It differs from medical procedures in that it uses the whole herb, although there is often only one component of the plant that works effectively to manage the problem. Plants contain many natural chemicals or phytochemicals that interact with the active ingredient and help prevent any side effects. Medicinal herbs and spices are investigated for their suitability in daily diets for maintaining general wellness or preventing disease. In the past decade, natural health products, dietary supplements, foods with added value, or nutraceuticals have emerged due to the increasing demand for non-pharmaceutical healthcare products. Medical herbs and spices are potential sources for developing new, effective, and safe ingredients to capture a rapidly expanding opportunity in global marketplaces. This book presents up-to-date information on the chemical, pharmacological, and nutritional uses of medicinal herbs and spices in folk medicine, pharmaceuticals, the food industry, veterinary practice, and gastronomy.
... The chemical potential gradient, closely associated with the concentration gradient, represents the force exerted on each penetrant molecule during osmosis and diffusion. Under constant temperature and pressure conditions, the chemical potential (μ) can be described by the following equation [200,201]: Garlic (thiosulfinates, phenolic compounds and antioxidants) Temperature: 50 to 80 °C optimum temperature -< 70 °C [184] where, E G n is the partial derivative of the ratio of Gibbs free energy and number of moles of the penetrant. The chemical potential in a liquid phase as a function of temperature and water activity is determined by Eq. 10 [202]. ...
Drying is a crucial unit operation within the functional foods and biopharmaceutical industries, acting as a fundamental preservation technique and a mechanism to maintain these products' bioactive components and nutritional values. The heat-sensitive bioactive components, which carry critical quality attributes, necessitate a meticulous selection of drying methods and conditions backed by robust research. In this review, we investigate challenges associated with drying these heat-sensitive materials and examine the impact of various drying methods. Our thorough research extensively covers ten notable drying methods: heat pump drying, freeze-drying, spray drying, vacuum drying, fluidized bed drying, superheated steam drying, infrared drying, microwave drying, osmotic drying, vacuum drying, and supercritical fluid drying. Each method is tailored to address the requirements of specific functional foods and biopharmaceuticals and provides a comprehensive account of each technique's inherent advantages and potential limitations. Further, the review ventures into the exploration of combined hybrid drying techniques and smart drying technologies with industry 4.0 tools such as automation, AI, machine learning, IoT, and cyber-physical systems. These innovative methods are designed to enhance product performance and elevate the quality of the final product in the drying of functional foods and biopharmaceuticals. Through a thorough survey of the drying landscape, this review illuminates the intricacies of these operations and underscores their pivotal role in functional foods and biopharmaceutical production.
... It is important to mention that the application of osmotic dehydration is usually not enough to obtain a safe water activity of the material and therefore there is a need for applying additional preservation techniques such as drying that could help alleviate the issue. Some research previously focused on the drying of garlic [26][27][28]. However, no study presented the effect of drying on the garlic subjected to osmotic dehydration in a complex osmotic solution based on concentrated tomato juice and basil extract. ...
This study investigates the effects of osmotic dehydration on garlic clove halves using a low-pH osmotic solution with ascorbic acid, concentrated tomato juice, and basil extract (45° Brix). Samples, both dehydrated and fresh, were subjected to various drying methods. Physical properties, such as CT scan analysis, texture profile analysis (TPA), porosity, and density, were examined. Additional parameters like energy consumption, specific energy consumption, moisture content, water activity, and color change were evaluated. Osmotic dehydration reduced moisture content by over 7.5%. The specific energy consumption for microwave vacuum drying (MVD) was 95 kJ/g for osmotically dehydrated samples compared to 118 kJ/g for non-dehydrated samples. Drying times decreased by 24 min for MVD and 15% for microwave convective drying (MCD). The Weibull model best fit the drying kinetics, with R² values above 0.99 and RMSE below 0.03 for all methods. TPA tests showed no significant impact of osmotic dehydration on hardness, though drying methods significantly affected hardness, ranging from 49 N to 707 N. Color change was higher for osmotically dehydrated samples, reaching 37.09 for OD-CD compared to 29.78 for CD.
... This might be the result that infrared heating provides uniform and targeted heating, reducing the risk of localized over-heating, and is less likely to harm the cell integrity of garlic that can occur in freeze drying and in other drying techniques, potentially leading to better retention of allicin and antioxidants, on another side freeze drying occurs at very low temperature, typically below the freezing point of water and this minimizes the exposure of phenolic to heat, preventing thermal degradation. In another study by Zhou et al. (2016) on the bioactive parameters, antioxidant capacity, and a-amylase and a-glucosidase inhibiting properties of garlic. The results showed that phenolic and OSC may be successfully retained in dried garlic at a processing temperature of 60°C and a specific humidity of 10 g/kg as it provides controlled environment with consistent temperature and air flow, reducing the risk of overheating. ...
Garlic (Allium sativum L.) has been subject of fascination and research for centuries, owing to its diverse culinary and medicinal properties which further afftects its agronomic significance. This review paper delves into the multifaceted aspects of the garlic crop, aiming to unveil the various dimensions that make it truly remarkable botanical wonder. Among the plethora of compounds found in garlic, allicin an organosulfur compound (OSC), has emerged as a focal point of interest for researchers and health enthusiasts alike. Allicin is known for its powerful antimicrobial, antioxidant, and cardiovascular benefits, rendering garlic a potent natural remedy and a valuable addition to realm of alternative medicine. Allicin's synthesis, bioavailability, and mechanism behind its medicinal effects has also been discussed. Furthermore, the impact of various drying techniques on the allicin content of garlic has been examined. As the understanding of allicin's health benefits continues to evolve, this comprehensive review contributes valuable insights into optimizing garlic's drying methods to preserve and enhance the allicin content, thus maximizing its therapeutic potential. By synthesizing existing knowledge, we provide a platform for future research to address gaps in the field of garlic drying technology and its profound impact on allicin retention for various health applications.
... These studies (Chan et al., 2014;Chhokar et al., 2009;Mishra et al., 2017) had lower TPC than our present study, whereas Alide et al. (2020) showed higher TPC and TFC. The differences in the TPC and TFC values found in these studies could be attributed to variations in the variety, climate, maturity, and processing of the garlic samples (Kim et al., 2013;Selen, 2019;Wongsa et al., 2023;Zhou et al., 2017). ...
Garlic, belonging to the genus Allium, is renowned for its rich antioxidant potential. Snow Mountain garlic (SMG) (Allium ampeloprasum) has been traditionally used for medicinal purposes because of its higher antioxidant potential. Considering its potential in medical therapies, we compared the antioxidant activity of SMG with a novel variety of Allium sativum, Hisar garlic 17 (HG17). Comparative antioxidant activity data (2,2‐diphenyl‐1‐picrylhydrazyl and 2,2‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) revealed the higher antioxidant activity of HG17 than SMG, which prompted us to conduct a comprehensive phytochemical investigation to elucidate the factors contributing to antioxidant potential of HG17. To get a detailed antioxidant and phytoconstituents profiling, we differentially extracted HG17 by processing it in different forms (fresh, dry, heated, and aged) with two solvents (50% methanol and n‐butanol). Our data (antioxidant activities, total phenolics, and flavonoids) showed that dry garlic methanolic extract (DgM) had maximum potential than other HG17 forms/solvents, which concludes that different extraction techniques had direct impact on the phenolics/flavonoids and antioxidant potential of the extracts. Further, phytochemical analysis of HG17 extracts by high resolution liquid chromatograph mass spectrometer quadrupole time of flight validated the maximum potential of DgM. LCMS revealed the presence of garcimangosone C, osmanthuside A, and protoaphin aglucone polyphenols exclusively in DgM compared to other HG17 extracts, which possibly contributing in its high antioxidant potential. The overall differential extraction and LCMS data of HG17 strongly depict that it may be used as an alternative of SMG under diverse medical applications. HG17 higher antioxidant potential and rich array of unique phytochemicals make it valuable for food and pharmaceutical industries to integrate into functional foods/therapeutics.
Practical Application
Garlic unique phytochemical composition and its remarkable ability to scavenge different radicals make it valuable therapeutic asset to mitigate diseases associated with oxidative stress. SMG is well known for its anti‐arthritic and anti‐inflammatory properties. HG17 showed higher antioxidant potential than SMG and can be used as an alternative of SMG for anti‐arthritic properties.
... The 325W 400 mmHg among drying samples and NPD-350W among frying samples displayed the highest DPPH and ABTS values. Similarly, Zhou et al. [44] reported that dried garlic samples showed higher antioxidant activity with increasing infrared power. In the frying process, NPD samples had higher DPPH values than PD sample, due to the longer thermal treatment. ...
In this study, the effects of different drying (180–325 W and 100–400 mmHg) and frying (250–350 W and 400 mmHg) parameters on phenolic compounds, bioaccessibilities, antioxidant activities, and α-glucosidase inhibitory activities of apple chips dried and fried by vacuum-combined infrared radiation were investigated. Catechin (12.15–34.48 mg/kgDM), epicatechin (34.33–137.07 mg/kgDM), procyanidin B1 (14.07–30.05 mg/kgDM), procyanidin B2 (48.10–95.76 mg/kgDM), procyanidin C1 (14.95–42.97 mg/kgDM), chlorogenic acid (262.70–397.97 mg/kgDM), and rutin (0–5.94 mg/kgDM) were identified in apple chips. The phenolic content of apple chips increased with increasing infrared power during the drying and frying process. The phenolic contents of fried apple chips were generally higher than dried apple chips. However, the bioaccessibility rates of total flavan-3-ols in dried apple chips were higher than those of fried apple chips. It was determined that the initial total phenolic, flavonoid, and flavan-3-ol contents and antioxidant activity levels of the samples decreased after in-vitro gastrointestinal digestion. It was determined that all drying and frying samples showed higher α-glucosidase inhibitory activities (15.52–28.77 mg/mL) compared to acarbose (30.87 mg/mL). The apple chips dried and fried by infrared radiation had higher phenolic content, antioxidant activity, bioaccessibility, and α-glucosidase inhibitory activity than their counterparts (convectional drying and deep-fat frying, respectively). Vacuum-combined infrared drying and frying is a promising method to preserve the phenolic content, antioxidant, and antidiabetic activities of apple chips, especially at high temperature applications. Further research is needed on new designs for the production of fruit chips using infrared radiation and their effects on bioactive components.
Graphical abstract
... In both fresh and dried peaches, the total phenolic content (TPC) was ascertained following a slightly modified procedure, originally reported by Zhou et al. [19]. A 0.50 g sample of pre-weighed peach powder (dry basis) was mixed with 20 mL of an 80% methanol solution. ...
The aim of this research was to systematically evaluate the impact of varying ripeness stages (categorized into five distinct levels: I, II, III, IV, and V) on the drying behavior, moisture status, cellular injury, texture, rehydration properties, bioactive compounds, antioxidant activities, and sensory attributes of peaches. The ultimate goal was to identify the optimal ripeness stage of peaches for hot-air drying. Results demonstrated that significant disparities exist in drying characteristics among peaches of different ripeness levels. Peaches at ripeness stage III exhibited the most efficient drying kinetics, characterized by the shortest drying duration, highest drying rate, and maximum moisture diffusion coefficient. This was followed by peaches in stages II, I, IV, and V, the differences being attributed to variances in moisture mobility, content, and cellular injury. Additionally, stage III peaches displayed optimal levels of ascorbic acid, total phenolics, antioxidant capacity, and rehydration ratio. Conversely, peaches at stage V excelled in visual appearance, sugar-to-acid ratio, and flavor profile. Consequently, peaches at ripeness stage III are recommended for hot-air drying due to their superior drying efficiency and quality attributes. This study serves as a theoretical foundation for future work on quality categorization and drying methodologies for peaches.
... Te level of phenolic components in dried orange snacks was generally found to be signifcantly lower than in the fresh sample. Long-term heat treatments may cause permanent chemical changes in phenolic compounds, which could explain the degradation of phenolics after drying [100]. Additionally, phenolics can degrade due to other factors such as the activity of oxidative enzymes (polyphenol oxidase, peroxidase), organic acid level, sugar concentration, and pH. ...
Citrus fruits, regarded as a prominent fruit crop, are cultivated extensively around the globe and orange (Citrus sinensis L.) is a widely cultivated popular member of the citrus family. Dried oranges have gained recognition as a healthy snack option among consumers and worldwide markets due to the absence of additional ingredients such as sugar and chemicals, whilst yet containing significant natural beneficial components. The drying method is very intriguing due to its ability to facilitate the efficient production, packaging, storage, and transportation of dried oranges at a cost-effective price. In this study, the effects of microwave pretreatment (Mpt) (90 W, 30 min) on hot air drying (HTAD-MW) (60, 70, and 80°C) were investigated, along with the effects on the drying kinetics, rehydration capacity, and quality properties of the orange snack including phenolic compounds (vanillic acid, gallic acid, epicatechin, hesperidin, naringenin, chlorogenic acid, sinapic acid, and o-coumaric acid), antioxidant capacities (with DPPH, FRAP, and CUPRAC methods), and ascorbic acid contents. For modeling the kinetics of orange snack drying in all tests, logarithmic, Wang and Singh’s, diffusion approach, two term, and Wang and Sing’s models performed best. Hot air drying (HTAD) at 70°C applied orange snacks showed the lowest △E ∗ ab value, and the color values were close to those of fresh orange slices. The levels of total and individual phenolics, antioxidant capacity (AC), and ascorbic acid (AA) in dried orange snacks were found to be significantly lower ( p < 0.05) than in the fresh orange slices. Results also showed that HTAD-MW-applied orange snacks contained more total phenolic (TP) content, individual phenolic content, and AC but lower AA than HTAD-applied samples. The highest amount of phenolic compound was hesperidin for fresh and dried orange snacks. The method that best preserves the TP content and AC of dried orange snacks was found at the drying condition of HTAD-MW at 60°C. As a conclusion, it was suggested that the use of microwave and hot air combination is a promising method to introduce a new functional healthy snack to the dried product market with high quality.
... Moreover, when applying 100 W IR-HPD, there was no statistical change in p-salicylic acid (p>0.05). The degradation of phenolics after the drying process may be explained by irreversible chemical changes in phenolic compounds, which may occur due to long-term heat treatments (Zhou et al., 2017). Moreover, other factors such as the activity of oxidative enzymes (polyphenol oxidase, peroxidase), organic acid content, sugar concentration, and pH can also lead to phenolics deterioration. ...
An infrared-assisted heat pump drying (IR-HPD) was designed and used for drying of mushroom slices at three different infrared (IR) powers (50, 100, and 150 W) and a fixed drying temperature of 40°C and air velocity of 1 m/s. The changes in total phenolic content (TPC), total antioxidant capacity (TAC) and individual phenolic contents bioaccessibility, drying characteristics, and colour values of mushroom slices were investigated. IR-HPD provided 13.11 to 30.77% higher energy savings than HPD and reduced drying time between 9.48 and 26.72%. Page, Modified
Page models were considered the best for predicting the thin layer drying behaviour of mushroom slices. The effective moisture diffusivity (Deff) value increased with IR power and ranged between 6.491x10-10 and 9.023x10-10 m2s-1. The contents of TPC, TAC, and individual phenolics in mushroom slices were significantly reduced (p<0.05) after drying. In vitro the bioaccessibility of phenolic compounds and TAC generally decreased, whereas TPC bioaccessibility was increased. Colour values were decreased except for a* value that increased after drying. Thermal imaging
results showed that IR lamps increase the temperature of the products in the middle close to the lamp by approximately 1.5°C. In addition, thermal imaging gave a better understanding and visualised the effect of different power IR lamps on the temperature distribution of the products according to their distance from the
lamp. As a result, drying mushrooms with a hybrid drying system combined with IR and heat pump dryer provided higher energy savings than HPD, reduced drying time, and maintained the physical and nutritional characteristics of mushrooms. Overall, the use of IR-HPD is an alternative tool that allows us to obtain high-quality
dried mushrooms with good nutritional attributes and a high amount of bioaccessible polyphenols.
... However, the properties of garlic can differ significantly depending on the cultivar, conditions of cultivation, drying conditions, and storage time and conditions [41,42]. The levels of soluble sugar were reported to decrease during storage, and the contents of total polyphenols and organosulfur compounds reached maximum values at 6 and 8 weeks, respectively, and then decreased significantly [43]. ...
Garlic is known to be rich in antioxidants, inhibit the proliferation of various cancer cells, and hamper cancer formation and growth, but various forms of garlic can differ greatly in these respects. This study aimed to compare the antioxidant properties of acetone, ethanol, and aqueous extracts of fresh Polish and Spanish garlic, black and granulated garlic, as well as fresh and dried ramsons. Extracts of black and granulated garlic showed the lowest total antioxidant capacity (TAC). The content of phenolic compounds correlated with TAC measured by ABTS• decolorization and FRAP methods, and with the results of FRAP and DPPH• decolorization assays. Garlic extracts inhibited the proliferation of PEO1 and SKOV3 ovarian cancer cells and, usually to a smaller extent, MRC-5 fibroblasts. PBS extracts of fresh Spanish garlic showed the highest potency for inhibition of proliferation of PEO1 cells (IC50 of 0.71 µg extract dry mass/100 µL medium). No significant correlation was found between the potency for inhibition of proliferation and the content of phenolics or flavonoids, confirming that phenolics are the main determinants of TAC but do not contribute significantly to the antiproliferative effects of garlic.
... TPC and antioxidant activity were also shown similar changes during the drying processes. According to the antioxidant activity results of garlic (Zhou et al., 2017) and pear (Liu et al., 2019) dried with infrared dryer, an increase in antioxidant activity was observed with increasing IP. While, for the HMF, DPPH and ABTS values, the differences among the IPs in infrared drying and temperatures in convectional drying were found to be statistically significant (p<0.05), for TPC values was insignificant (p>0.05). ...
In this study, the quality characteristics of pear slices dried in vacuum-combined infrared dryer equipped with a two-way infrared heating (100-300 W infrared power) and convectional dryer (40-70 °C) were comparatively investigated. Increasing infrared power in vacuum-combined infrared dryer decreased the drying time. However, the differences between vacuum pressures (100 mmHg and 250 mmHg) were generally negligible. Drying process at 200 and 300 W IP under vacuum was approximately 2- and 2.5-times shorter than conventionally drying at 55 and 70 °C, respectively. Although a very low amount of HMF in dried pear slices by the conventional dryer was detected only at 70 °C after 300 min, high amounts of HMF was detected at 300 W after 120 minutes. The rehydration rate of pear slice dried with vacuum-combined infrared dryer was higher than those of pear slice dried with conventional dryer. Syringic, chlorogenic and ellagic acids were identified in dried pear samples. Chlorogenic acid was found to be the most among phenolic compounds in dried pears. While the ellagic acid was not detected in fresh pear, dried pears had ellagic acid content (8.14-16.93 mg/kg d.m.). It was found that total phenolic content, ABTS and DPPH values of dried pears by vacuum-combined infrared dryer was lower than those of dried sample by conventional dryer. The pear slices dried at 300W and 250 mmHg had the highest sensory scores. The results show that the vacuum-combined infrared drying provided a shorter drying time and better sensory quality for dried pear compared to conventional drying.
... changes to the chemical structure of polyphenols. 36 The lowest TPC and TFC in samples dried at 40°C were related to the long drying times and high enzyme activity of PPO under 40°C. However, drying at the highest temperature (70°C) used in this study did not result in more loss in phenolic compounds. ...
Background
Infrared‐assisted spouted bed drying (IRSBD) is an innovative hybrid drying technology based on infrared drying and spouted bed drying, which has the advantages of higher drying efficiency and better uniformity. Temperature is an important process parameter that affects drying characteristics and product quality. Considering the overall quality of the product, drying at a constant temperature may not be the best solution. However, there is a lack of research on dynamically varying drying schemes. In this study, the effects of constant and variable temperature drying processes on the drying characteristics, uniformity, energy consumption, and quality of Chinese yams were evaluated.
Results
The shortest drying time and lowest energy consumption were obtained by IRSBD at 70 °C, followed by staged rising temperature drying (SRTD). However, SRTD achieved the best drying uniformity. The Peleg model could describe the dehydration kinetics of dried yams well (R² > 0.99). A high drying temperature (70 °C) favored the preservation of bioactive compounds (polyphenols and flavonoids) and gave the best antioxidant activity and equilibrium rehydration ratio of dried yams but resulted in poor color. Samples dried with SRTD showed comparable good antioxidant activity and better color than those dried at 70 °C.
Conclusion
A reasonable variable temperature drying scheme using IRSBD is considered to be better when considering the drying performance and overall quality of the products. © 2022 Society of Chemical Industry.
... Boateng et al. (2021) reinforced that infrared has a high penetration capacity so that it can break more cells and thus release more phenolics. Zhou et al. (2017) indicated that there is an energy level transition at the molecular level, converting kinetic energy into thermal, thus releasing more compounds. ...
This study aimed to evaluate the effectiveness of pretreatments on papaya drying behavior and quality parameters. The pretreatment consisted of submerging the samples in ethanol or distilled water for 20 min. The ultrasonic step was conducted in an ultrasonic bath (25 kHz). Samples were dried in an infrared dryer and a convective oven at 60°C. The material pretreated with ultrasound and ethanol and submitted to infrared drying presented the shortest drying time (84 min). The two‐term exponential model was the most predictive for the drying data fitting. All dried samples showed water activity values below 0.60. Among the pretreatments performed, the use of ultrasound associated with ethanol was more effective in reducing losses of total phenolics, ascorbic acid, and antioxidant activity of dried papaya when compared to the use of water. Infrared drying of the fruit pretreated with the combination of ultrasound and ethanol resulted in no significant difference from the untreated papaya concerning the evaluated quality parameters.
Practical applications
The consumption of tropical fruits and their derived products has increased in national and international markets, due to the growing recognition of their nutritional properties and subsequent use in the food industry. The presence of nutrients such as bioactive compounds, demonstrates their potential for use in different sectors, increasing the added value of the cultivar. Thus, this study represents a contribution to society, recognizing and valuing the consumption of fruit, contributing to the nutritional conditions of the population, favoring food and nutritional security, and conservation of the species. It also allows, with the use of pretreatments and different types of drying, advances, and information about food preservation methods that have a low environmental impact and the exploration of new forms of fruit consumption, increasing its shelf life and facilitating their transport and marketing.
... In vitro and animal studies have shown that garlic can suppress many types of cancer, such as blood, bladder, stomach, breast, oral cavity, lung cancer, colorectal cancer, skin cancer, and uterine cancer [71][72][73]. Epidemiological studies have shown that garlic has a role in the prevention of cardiovascular diseases due to the presence of these bioactive components [74]. Garlic consumption may protect the brain from loss of intellectual capacity and may reduce the risk of Alzheimer's disease [75]. ...
Garlic (Allium sativum L.) is one of the greatest gifts of natural medicine and the oldest medicinal herbs that is cultivated all over the world. It is a widely used spice plant with well-known medicinal properties. Garlic is an important raw material of plant origin with observed and proven positive effects on the human body. A. sativum L. belongs to the most extensively studied medicinal herbs from genus Allium. In the past few decades, its biologically active compounds have been analyzed for their therapeutical properties. The most essential biologically active compound discovered in A. sativum is allicin, working synergistically with other phytochemicals in the prevention of many diseases. Preparation of garlic extractions can be done in liquid form and solid form. The composition and bioactivity of the extraction depend on the strain, age, method of preparation, and consumption method. When extracted and isolated, the bioactive compounds of garlic show a wide range of beneficial health effects: platelets inhibitory and antithrombic activities, hepatoprotective, antimicrobial, antihyperglycemic, antidiabetic, and antitumor. The present chapter describes botanical characterization of garlic, its chemical composition regarding bioactive compounds, and its health benefits.
... Changes in the phenolic compounds and the degradation mechanisms depended on the drying process applied, and the type of phenolic compounds studied. The total phenolic compounds in dried garlic slices were significantly enhanced with drying temperature from 50° to 80 °C at 1575 W during infrared drying [39]. Analysis of individual phenolic compounds in figs (Ficus carica L.) indicated a higher content of all phenolic groups determined after the oven-drying process [40]. ...
Present investigation studies the effect of convective hot-air drying on the contents of allicin content and phenolic compounds, antioxidant activities, α-amylase and α-glucosidase-inhibiting properties of garlic (Allium sativum L.). Thin garlic samples were chopped in single-layer dried in a high precision, ICT-controlled lab dryer at 50-80 °C, with specific humidity of 10 and 20 g water per kg of dry air and a constant air velocity of 0.5 m/s. Phenolic compounds were qualitatively and quantitatively measured. In addition, inhibitory potential against α-amylase and α-glucosidase in dried garlic was examined in vitro. The combination of lower hot-air drying temperatures and lower humidity levels of hot air caused the content of individual phenolic acids and allicin in garlic to increase while preserving a high percentage of α-amylase and α-glucosidase inhibition. A high negative correlation was observed between the total phenolic content, antioxidant activities, α-amylase inhibition and α-glucosidase inhibition, whereas a moderate positive correlation (0.752, p < 0.05) was observed between allicin, α-amylase and α-glucosidase inhibition. The findings indicated that dried garlic prepared at the hot-air drying temperature of 60 °C and specific humidity of 10 g/kg could effectively retain phenolic and organosulfur compounds. These extracted compounds can be potential functional ingredients used for dietary treatment during the early stage of hyperglycemic. The subsequent investigation could combine the traditional hot-air drying approach with microwave or vacuum drying, which may significantly minimize processing time while retaining a high retention rate of garlic's functional ingredients and bioactive activities.
... Also according to EL-Mesery et al. [10], and Zhou et al. [42], infrared heating generates temperature gradient that results in vapour thermo-diffusion from inner to surface of drying sample unlike the ordinary diffusion displayed by convective dryers. However, such heating characteristics of infrared has a degradative effect on heat-sensitive compounds such as allicin, vitamins, phycocyanin when compared with hot air drying system [40,43]. ...
As part of improving energy efficiency and quality of dried product, a hybrid infrared dryer was constructed by combining infrared (IF) and hot-air heating (HAD) systems and can be used to dry fruits and vegetables. This hybrid drying system is composed of hot-air drying and infrared heating system and was tested by drying garlic slices (3 mm) at 0.7 m/s using three temperatures of 40, 50, and 60 °C and infrared heating intensity of 1500, 2000, and 3000 W/m². The Newton, Page, and Wang & Singh models were used to predict the moisture ratio (MR) and the results show that all the tested models exhibited MR prediction in garlic. The hybrid infrared dryer was efficient in energy consumption by conserving energy by 533–552% when compared with HAD drying system. Also, there was significant (p<0.05) improvement in rehydration capacity, allicin content and colour when compared with HAD and IF drying techniques. In effect, this hybrid dryer could provide a better drying alternative for industrial applications as it has the potential of saving energy and improving the quality of dried products.
... Garlic, which is a squamous bulb belonging to the Allium family of Liliaceae, is one of the ancient herbs ever known and used by human as spice, food and folklore medicine over 400 years. Garlic contains abundant active compounds, such as allicin, polysaccharides and polyphenols, which contribute to the characteristic flavor and the biological activity of the garlic [10][11][12]. The medicinal health effects of garlic have a huge connection with the polysaccharides which it contains. ...
The purpose of this study was to optimize modification conditions of selenized garlic polysaccharides (sGPS) and investigate its structural characterization, immune and antioxidant activities. Herein, selenized garlic polysaccharides (sGPS) were prepared using by HNO3-Na2SeO3 selenylation method. And then modification conditions of sGPS were optimized through L9 (3⁴) orthogonal test. The structural characterization of sGPS were identified by the Fourier-transform infrared (FT-IR), Solid-State nuclear magnetic resonance (NMR) spectra, X-ray diffraction (XRD) and thermogravimetric (TGA). The morphology of sGPS was detected using scanning electron microscope (SEM) and transmission electron microscope (TEM). In vivo investigation showed that sGPS significantly improved serum hemagglutination-inhibition (HI) antibody titers against Newcastle disease virus, enhanced secretory IgA (sIgA), IFN-γ, IL-2 secretion in jejunum and trachea irrigation compared with vaccine immunized control group. Furthermore, it showed that sGPS had some effects on the antioxidant activities in livers of chickens. In conclusion, the optimal modification conditions of sGPS were as follows: reaction temperature was 70 °C, the dosage of Na2SeO3 was 400 mg and reaction time was 6 h. The selenylation modification of garlic polysaccharides (GPS) could improve its immune and antioxidant activity in chickens.
... Low pH during thermal treatment recorded better betanin retention as compared to high pH. Beetroot fermentation at 4 °C preserved betanin up to 10-15mg/ 100ml extract up to 32 days in refrigerated storage [308] Beta-carotene • Refrigerator storage (4 °C) led to 40% decrease in beta-carotene in carrot and 25% decrease was recorded on freezer ( −16 °C) storage for 20 days [309] • Thermal degradation resulted in reduced carotenoids content from 15.28 to 9.34 mg/100 g (red) and 24.5 to 22.12 mg/100 g (orange) in carrots [310] • Pressure cooking resulted in decreased β-carotene content of commonly consumed vegetables [311] ( continued on next page ) and capsicum as compared to fresh samples whereas these were higher in corn (22%) and broccoli (14%) over blanching [317] Chlorophylls • Low-pressure (100 and 250 MPa) treatments for 5 min in spinach were found to be beneficial for chlorophylls retention [318] • High-intensity pulsed electric fields (35 kV/cm for 1,980 μs in bipolar mode) conditions in broccoli juice contributed greater content of chlorophylls than that of controlled samples [319] • Maillard Reaction Products (prepared from glucose and glycine heated at 90 ˚C in an air circulating oven, 12 hours) decreased the loss of chlorophylls contents in green peas [320] • Metalized polypropylene (300 gauge) led to higher levels of chlorophylls in green leafy vegetables ( Alternathera sessilis and Amaranthus polygonoides ) than other storage methods such as high-density polyethylene (300 gauge), polypropylene (200 gauge) and storage at room temperature for 3 months [321] • UV-C treatments for 30 min for 7 days on fresh garden cress leaves delayed yellowing and chlorophylls degradation hence, increased the chlorophylls content [322] Flavones • Garlic extract prepared by high hydrostatic pressure (500Mpa) for various durations resulted in decreased allinase and anti-microbial activity [323] • Ginger-garlic paste treated by microwave heating stored for 3 months had significantly affected the acidity [324] • Enhanced activity of polyphenol oxidase and peroxidase enzymes was observed at thermal treatment (200 MPa) whereas it was found reduced significantly at 400 and 600 MPa [325] • Dried garlic slices at 50 to 80C at 1,575 W significantly resulted in enhanced total phenolic compounds [326] on the other hand, are the residual fraction that is left behind after the vaporization of the former [331] . Under high temperature and acidic conditions, isomerization occurs which changes the predominant all-trans carotenoids to mixed cis-trans isomers which in turn shifts the absorption spectrum of the pigment and ultimately affects the color expression of the vegetables. ...
Vegetables are essential protective diet ingredients that supply ample amounts of minerals, vitamins, carbohydrates, proteins, dietary fiber, and various nutraceutical compounds for protection against various disease conditions. Color is the most important quality parameter for the farmers to access the harvest maturity while for the consumer's reliable indices to define acceptability or rejection. The colored vegetables contain functional compounds like chlorophylls, carotenoids, betalains, anthocyanins, etc. well recognized for their anti-oxidant, anti-microbial, hypolipidemic, neuroprotective, anti-aging, diuretic, and anti-diabetic properties. Recently, there has been a shift in food consumption patterns from processed to semi-processed or fresh fruits and vegetables to ensure a healthy disease-free life. This shifted the focus of agriculture scientists and food processors from food security to nutrition security. This has resulted in recent improvements to existing crops like blue tomato, orange cauliflower, colored/black carrots, with improved color, and thus enriched bioactive compounds. Exhaustive laboratory trials though are required to document and establish their minimum effective concentrations, bioavailability, and specific health benefits. Efforts should also be directed to breed color-rich cultivars or to improve the existing varieties through conventional and molecular breeding approaches. The present review has been devoted to a better understanding of vegetable colors with specific health benefits and to provide in-hand information about the effect of specific pigment on body organs, the effect of processing on their bioavailability, and recent improvements in colors to ensure a healthy lifestyle.
Spent sour cherry pomace (SSCP), a by-product from Maraschino liqueur production, is a rich source of polyphenols worth valorizing. However, its high moisture content promotes microbial spoilage and reduces extraction efficiency per unit weight, limiting their valorization. This study evaluated the impacts of freeze-drying and oven-drying and different particle sizes (≤100, ≤200, and ≥ 200 µm) for efficient ultrasound-assisted recovery of polyphenols. The moisture content decreased by 83.33 % in freeze-drying and 84.17 % in oven-drying, resulting in a higher yield of bioactive compounds from a given sample weight. Smaller particle sizes significantly improved extraction efficiency, probably due to increased surface area. Freeze-dried samples at ≤ 100 µm had the highest total phenolic content (224.32 ± 3.13 mg gallic acid equivalent/L), total monomeric anthocyanin content (9.48 ± 0.12 mg/L), and ferric reducing antioxidant power (487 ± 3.58 mg Trolox equivalent/L), along with the highest levels of epicatechin (1.15 ± 0.11 mg/L) and cyanidin-3-rutinoside (9.81 ± 0.06 mg/L). These results suggest that freeze-drying preserves bioactive compounds better than oven-drying. SEM images from post-extraction SSCP pellets showed a generally identical cell disruption among all the samples, highlighting that the differences in the extract properties are highly dependent on the sample preparation method (i.e., drying process), despite the key role of the extraction process. The antioxidant activity of the extracts from oven/freeze-dried SSCPs at ≤ 100 µm was evaluated in soybean and sunflower oils using the Rancimat method. The extract competency in delaying lipid oxidation in the oils showed their potential as natural antioxidants for future food applications.
The experiments were conducted at different levels of infrared power, airflow, and temperature. The relationships between the input process factors and response factors’ physicochemical properties of dried garlic were optimized by a self-organizing map (SOM), and the model was developed using machine learning. Artificial Neural Network (ANN) with 99% predicting accuracy and Self-Organizing Maps (SOM) with 97% clustering accuracy were used to determine the quality characteristics of garlic. Specifically, five key areas were identified, and valuable insights were offered for optimizing garlic production and improving its overall quality. The (aw) values for the sample ranged from 0.43 to 0.48. The maximum vitamin C content was 0.112 mg/g, followed by an air temperature of 40 °C and 0.7 m/s air velocity under 1500 W/m². The total color change values increased with IR and higher air temperature but declined with higher air velocity. Also, the garlic’s flavor strength, allicin content, water activity, and vitamin C levels decreased as the IR and air temperature increased. The results demonstrated a significant impact of the independent parameters on the response parameters (P < 0.01). Interestingly, the machine learning predictions closely matched the test data sets, providing valuable insights for understanding and controlling the factors affecting garlic drying performances.
The Infrared (IR) heating technology provides the advantages of energy-efficient rapid heating with high heat transfer rates compared to conventional heating mechanisms such as conduction and convection. However, exposure to IR induces nutritional losses and the development of undesirable chemical changes in the foods. This chapter aims to highlight the studies on the degradation of proteins, lipids, phenolics, vitamins, flavors, phytopigments, and antioxidants in various food groups. Additionally, the formation of different potentially hazardous and carcinogenic by-products resulting from thermal damage, such as furosine, acrylamide, aromatic amines, hydrocarbons, 5-hydroxymethyl-2-furaldehyde, pyridines, etc. are discussed. This chapter also provides an insight into the mechanisms by which IR heating leads to the inactivation of food spoilage and pathogenic microorganisms and their spores, including E. coli, S. aureus, Bacillus subtilis, Aspergillus niger, and Pseudomonas sp.
This study aims to examine the energy-related aspects of ahybrid convection-radiationdrying technique employedinthedryingprocessof garlicslices. Several factors, including infraredradiationintensity(1500, 2000,and3000W/m2),airtemperature(40,50,and60◦C),andairflowratesofthedryingchamber(0.7,1.0, and1.5m/s)wereevaluatedtooptimizetheresponsesofdryingtime(min),energyconsumption(kJ),thermal efficiency(%),andspecificenergyconsumption(MJ/kg).Furthermore,anArtificialNeuralNetworkmodelwas employedtopredict theeffectsof theparametersaboveonthedryingsystem’sspecificenergyconsumption, energy consumption, drying time, and thermal efficiency. The obtaineddatawere analyzedusing a selforganizingmapandprincipal component analysis. Interestingly, thefindings showedthat increasingtheair temperatureandinfraredradiationintensityledtoshorterdryingtimes,whilehigherairflowratesresultedin longerdryingdurations.Additionally,itwasfoundthathigherinfraredintensityandairtemperature,combined withlowerairflowrates,improvedtheenergyindices.Increasingtheairvelocityto1.0and1.5m/satthesame air temperatureandradiation intensityresulted inaconsiderable increase indrying timeby9and22.7%, respectively.Thelowestefficiencyvalueof10.1%wasobservedat40◦Ctemperatureandanairvelocityof1.5 m/s.TheArtificialNeuralNetworkmodeldemonstratedhighaccuracywithaRootMeanSquareErrorof0.05 andanoverallaccuracyof (95%) inpredictingthedryingparameters.Notably, theself-organizingmapvisualizationrevealedthathigherairtemperaturesandradiationcorrespondedtolowerdryingtimes,energyconsumption,andspecificenergyconsumption.Conversely,higherairflowratesresultedinincreaseddryingtime andenergyconsumption.Thepresentstudysuggestedthat60◦C,3000W/m2and0.7m/sareoptimumconditionsforefficientlydryinggarlicslicesunderthehybriddryer.Thisinvestigationaddressesthelimitationsand deficienciesofpreviousworkonenergyoptimizationandefficiencyanalysisofgarlicunderahybriddryerwith infraredheatingsystems.Furtherstudiesontheeconomicfeasibilityofapplyingsuchasystemforsampledrying andtheimpactofdryingonthethermalbehaviorsoftheproductsneedadditional investigation.
Featured Application
The research provides valuable insights for designing garlic-based products with enhanced antimicrobial effectiveness for both food preservation and health applications.
Abstract
The health properties of garlic (Allium sativum L.) are attributed to thiosulfinates, flavonoids, phenols, and bioactive polysaccharides. These compounds, however, can degrade during processing methods. As hot air-drying is a commonly used preservation method due to its relatively simple operation, this study investigated the effects of garlic slices dried at various temperatures (50, 70, and 90 °C) on the growth kinetic parameters of model strain Escherichia coli ATCC 25922, the total thiosulfinate content (TTC), and the total phenolic content (TPC). Observations showed that the concentration of garlic extracts was a significant factor influencing the kinetics of bacterial growth, while the garlic drying temperature appeared to have no effect on E. coli activity. Analysis of TTS in fresh and dried garlic did not reveal statistically significant differences in their levels. However, hot air drying at 50 °C significantly reduced the TPC by nearly 25%, whereas drying garlic at higher temperatures (70 °C and 90 °C) did not lead to a significant loss in TPC compared to the raw samples. The determined growth kinetic parameters of the tested E. coli strain could serve as a basis for selecting optimal drying process conditions and extract concentrations when designing garlic products with enhanced antimicrobial properties.
The Astragalus membranaceus (AM) slices were dried using three infrared drying techniques, including near infrared drying (NIR), mid infrared drying (MIR), and far infrared drying (FIR). Studies and discussions about the impacts of infrared temperature, power, slice thickness and wavelength on the drying properties, energy consumption, and associated performance were conducted. Results showed that the drying rate increased with increasing infrared temperature and wavelength, and with decreasing slice thickness, whereas the drying process was not significantly influenced by the infrared power. The drying efficiency of FIR was superior to that of NIR and with the increase of temperature, this improvement became more obvious. FIR drying was the fastest with the least energy consumption among the three drying methods. Rehydration ratio and color change of AM slices were proportional to infrared temperature and wavelength, but inversely proportional to slice thickness. The effective moisture diffusion coefficients of AM slices under NIR and FIR drying ranged from 0.49244×10−9 to 1.16352×10−9 m2/s and 1.00432×10−9 to 2.51135×10−9 m2/s, respectively.
Three emerging non-thermal pretreatment methods, including cold plasma, ultrasound, and ozone water, were utilized to pretreat garlic slices before drying process. The garlic slices were then dried by hot air drying at 60 °C. The study investigated the drying kinetics, color, rehydration ratio (RR), allicin content (AC), total phenolic content (TPC), antioxidant activity, and microstructure of the garlic slices. The results showed that ultrasound and ozone water pretreatment can significantly enhance drying kinetics. In comparison to untreated samples, garlic slices pretreated with ultrasound for 20 min exhibited a 55.96% increase in moisture effective diffusivity (Deff). Garlic pretreated with ultrasound exhibited the best rehydration properties, yet it retained the lowest levels of allicin content and antioxidant activity. Encouragingly, samples treated with ozone water demonstrated the best nutritional quality properties, with approximately 7.85% higher AC, 25.90% higher TPC, and 12.31% higher antioxidant activity compared to untreated samples. The study also emphasizes notable alterations in the microstructure of garlic resulting from various pretreatments. This research provides valuable insights into optimizing garlic drying processes using emerging non-thermal pretreatment techniques, showcasing their potential for industrial applications and quality enhancement.
The worldwide use of spices is related not only to their use as flavor and
odor adjuvants but also to their biological properties such as antioxidant,
anti-inflammatory, cytotoxic, and antiviral activities, among others, due to
the presence of bioactive compounds. These activities have made spices
interesting sources of nutraceuticals. The extraction of bioactive compounds
from spices must start with the selection of the appropriate drying process,
which is important also in the preservation of the spices by removing water
and minimizing possible chemical degradation. Afterwards, an extraction
technique is carefully chosen depending on the interested compounds.
These techniques can be either classical, such as maceration or Soxhlet
apparatus, or modern approaches involving eco-friendly procedures such
as microwave-assisted, enzyme-assisted, and supercritical fluids. Later on,
structural elucidation or quantification by using analytical techniques such
as gas and high-performance liquid chromatography (HPLC), mass spec-
trometry (MS), infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy must be carried out based on their chemical characteristics. These techniques have also been useful for the authentication and chemotaxonomical analysis of closely related species that have been used as adulterants in commercial preparations. Current trends aim to develop novel extraction techniques to enhance the production of nutraceuticals with the use of statistical tools such as chemometric measurements and response surface methodologies, thus allowing to explore metabolomics for a better knowledge of nutraceutical compounds found in spices.
The amalgamation of garlic's antibacterial potency with olive oil's nutritional benefits provides a natural, effective way to boost health and counters microbial threats. This study explored the antioxidant and antibacterial traits of garlic-enriched virgin olive oil (VOO) samples, focusing on various garlic forms (fresh, oven-dried, freeze-dried). Comparative analysis revealed fresh garlic's highest total phenolic content, flavonoid content, and strongest DPPH scavenging activity. GC/MS analysis unveiled distinct volatile profiles. Fresh garlic oil contained elevated allyl-methy-sulfide, diallyl-trisulfide, methyl-propyl-disulfide levels. Antibacterial evaluation displayed substantial inhibition zones, especially fresh garlic oil against E. coli, and oven-dried /freeze-dried garlic oils against P. aeruginosa. Lower Minimal Inhibitory Concentration (MIC) values for fresh garlic oil and freeze-dried garlic oil against both Gram-negative and Gram-positive bacteria signify potent antibacterial activity of garlic-enriched VOO. These findings underscore garlic-enriched VOO's potential as natural antibacterial agents, fortified with antioxidant traits, while emphasizing drying methods' role in shaping volatile compounds.
Garlic (Allium sativum L.) is used as both a food and traditional medicine for several illnesses throughout the world. 7 garlic cultivars (Novozamocky, Lumir, Mojmir, Havran, Garpel, Eden Rose, and Bjetin) were analyzed in this study. Since modern consumer demands encourage the consumption of foods with positive effects on human health, research into the nutritional properties and chemical composition of traditional crops, like garlic, is important. Knowledge of these properties could support the cultivation of cultivars with the highest content of bioactive compounds. Total polyphenol content (TPC) determined by Folin – Ciocalteau method ranged from 797.11 to 1183.98 mg GAE.kg-1 DM. Total flavonoid content (TFC) determined by the aluminum chloride method ranged from 15.96 to 28.18 mg CE.kg-1 DM. Antioxidant activity (AA) determined by the ABTS method ranged from 1.97 to 4.42 mmol TE.kg-1 DM. Antioxidant activity (AA) determined by the FRAP method ranged from 1.12 to 2.64 mmol TE.kg-1 DM. Statistical evaluation of results showed a difference between garlic cultivars. The highest antioxidant activity and the highest content of bioactive substances were determined in the cultivar Garpel. High positive correlations (p < 0.001) were determined between TPC and TFC (r = 0.746), TPC and AA ABTS (r = 0.862), TPC and AA FRAP (r = 0.922), TFC and AA ABTS (r = 0.792), TFC and AA FRAP (r = 0.808), and AA ABTS and AA FRAP (r = 0.896). Garlic is confirmed to be a natural source of antioxidants, polyphenols, and flavonoids.
Garlic, an asexually propagated crop, is the second important bulb crop after the onion and is used as a vegetable and medicinal plant. Abundant and diverse garlic resources have been formed over thousands of years of cultivation. However, genome variation, population structure and genetic architecture of garlic agronomic traits were still not well elucidated. Here, 1,100,258 single nucleotide polymorphisms (SNPs) were identified using genotyping-by-sequencing in 606 garlic accessions collected from 43 countries. Population structure, principal component and phylogenetic analysis showed that these accessions were divided into five subpopulations. Twenty agronomic traits, including above-ground growth traits, bulb-related and bolt-related traits in two consecutive years were implemented genome-wide association study. In total, 542 SNPs were associated with these agronomic traits, among which 188 SNPs were repeatedly associated with more than two traits. One SNP (chr6: 1896135972) was repeatedly associated with ten traits. These associated SNPs were located within or near 858 genes, 56 of which were transcription factors. Interestingly, one non-synonymous SNP (Chr4: 166524085) in ribosomal protein S5 was repeatedly associated with above-ground growth and bulb-related traits. Additionally, gene ontology enrichment analysis of candidate genes for genomic selection regions between complete-bolting and non-bolting accessions showed that these genes were significantly enriched in ‘vegetative to reproductive phase transition of meristem’, ‘shoot system development’, ‘reproductive process’, etc. These results provide valuable information for the reliable and efficient selection of candidate genes to achieve garlic genetic improvement and superior varieties.
In this study, energy and exergy analyses of the closed‐cycle infrared convective walnut drying were performed. The effects of the combined heat transfer, product‐source distance, and temperature‐relative humidity control on the food quality of walnuts and performance were investigated. Experiments were conducted with and without infrared lamp. The temperature and relative humidity of the drying air were set at 40 °C and 20%, respectively. The distance between the product and the infrared source was changed to 20 cm and 30 cm. The coefficient of performance values of the whole system changed between 1.56 and 2.34. Exergy efficiencies varied between 60.81‐88.19% without infrared and 72.73‐78.54% with infrared. Energy and time savings increased by 14.7% and 26.1%, respectively, with using infrared at a 20 cm distance compared to the convective system. The fatty acid composition of walnut samples and chemical properties of walnut samples such as total phenolic content, oil, ash, color, antioxidant activity, peroxide values, free fatty acid, conjugated trienes, conjugated dienes, saponification value, and iodine number parameters were analyzed. Food analysis results of all dried walnuts were in the acceptable range. As a result, energy and time savings were achieved with the desired food quality.
This work aimed to determine the effect of freeze drying (FD), hot air drying (HD), vacuum drying (VD), and infrared hot air drying (IRD) on the quality of two key kinds of garlic varieties (white and purple garlic). The quality including colors, bioactive compounds, and antioxidant capacities of dried garlic slices were investigated. The highest whiteness of dried white and purple garlic was found in FD treatments with its values at 87.04 and 81.89, respectively. The higher active substances contents and antioxidant capacities was found in dried purple garlic slices compared to the white ones under the same drying methods. The allicin contents in FD and IRD treated purple garlic were 2.60 and 2.67 mg/g and the total phenolic in these two samples were 5.93 and 4.33 mg/g. Meanwhile, the highest DPPH, ABTS and FRAP (6.64, 2.85 and 5.70 mmol TE/g. DW) was found in the IRD treated purple samples. Principal component analysis revealed the higher allicin contents, total phenolic contents, and antioxidant capacities in purple garlic slices compared to the white one in different drying methods. These results suggested that dried purple garlic under IRD treatment is more suitable for drying industrials than white garlic.
In a specially designed infrared oven equipped with a two‐way infrared heating and vacuum pump systems, the effects of drying parameters (100‐300 W infrared powers and 100‐250 mmHg vacuum pressures) on drying kinetics and quality properties of pear slices were comprehensively studied. The samples dried at 300 W had high HMF values (12.73‐95.68 mg/kg d.m). The highest sensory scores were observed in pear slices dried at 300 W and 250 mmHg. Six different mathematic models were taken into account to analyze the drying characteristics of pear slices, with the Wang and Singh model (R2=0.9996, χ2=0.0004 and RSME=0.0062) presenting the best prediction of the drying behavior. The effective moisture diffusivity values were 1.1829‐4.6684x10‐8. The activation energies for 100 and 250 mmHg vacuum applications were 44.21 and 43.89 kJ/mol, respectively. It was concluded that vacuum‐combined infrared dryer (300 W, 250 mmHg) could be a fast and economic method for drying pear slices.
Drying processes reduce the amount of available essential nutrients in dried plant-based foods to a large extent compared to fresh produce. This reduction is much larger than the differences in the final quality of products dried using various processing parameters and, in most cases, different drying methods. This aspect is, however, rarely highlighted. Here, the extent to which different convective drying methods reduce the nutritional content, namely vitamin C, carotenoids and phenolic content of dried fruits and vegetables, compared to fresh produce was quantified using literature data. The impact of different drying process parameters, such as air temperature, airspeed and relative humidity on the nutritional content of fruits and vegetables were compared. Results revealed that convective drying reduced the amount of vitamin C, carotenoids and the phenolic content of dried fruits and vegetables by up to 70%. The reduction in the residual vitamin C and carotenoid content of dried fruits and vegetables due to differences in air temperature (∼40%), airspeed (∼20%), and relative humidity (∼20%) is much less than the nutritional quality losses due to the drying process. The residual vitamin C, carotenoids and phenolic contents in convective-dried fruits and vegetables are ∼30% less than those in freeze-dried products. This study confirms that little absolute gains in nutritional quality can be achieved by opting for either an alternative drying method or optimizing processing parameters since the drying process already results in a low nutritional quality of dried products. As such, the remaining micronutrient concentration of dried products should not necessarily be a decisive criterion in selecting the most appropriate drying method or processing parameters for fruits and vegetables. Instead, other key performance indicators such as the drying time, energy consumption, or sensory properties such as color, texture, and rehydration capacity could eventually have a greater influence on the decision-making process.
Garlic (Allium sativum L.) is one of the most commonly grown vegetables and thanks to its sensory properties, it has an important place in numerous world cuisines. Garlic is also known for its health-promoting properties, which are attributed to its chemical composition. The health benefits of garlic depending on the content of biologically active compounds, which vary between cultivars and geographical areas. Seven cultivars of garlic, namely Sukoradsky, Zahorsky, Germidour, Mojmir, Karel IV., Arkus, Makoi, were analyzed in this study. This study aimed to determine the total polyphenol content, total flavonoid content, and antioxidant activity of garlic. Studied characteristics were analyzed by the UV-VIS spectrometry method. Total polyphenol content ranged from 430.26 to 640.04 mg GAE.kg-1 FW. Total flavonoid content ranged from 10.29 to 60.49 mg CE.kg-1 FW. Antioxidant activity measured by ABTS assay ranged from 1.098 to 1.955 mmol TE.kg-1 FW. Antioxidant activity measured by FRAP assay ranged from 0.63 to 1.467 mmol.kg-1 FW. Highest TPC, TFC, and AA were determined in the cultivar Mojmir. The lowest TPC and TFC were determined in the cultivar Zahorsky. The lowest AA was determined in the cultivar Sukoradsky. High positive correlations were determined between individual parameters.
Solar air collectors are integrated into the air source heat pump in order to increase the performance of the heat pump in cold climate regions. The evaporator air is heated by solar air collectors. In this study, two different types of solar air collectors which were textile based solar air collector and flat plate solar air collector were used. The thermal energy stored in the tank during the day was used to heat the room at day and night. The thermal storage tank was heated using three heating systems, textile based solar assisted air source heat pump (TSAHP), flat plate solar assisted air source heat pump (FSAHP) and air source heat pump (ASHP). In this study, energy, exergy and economic analysis of three different heating systems were performed. COP values increased by 32% in TSAHP and 21% in FSAHP compared to ASHP. Addition of solar air collectors to the ASHP heating system has been shown to improve thermal storage tank performance. Total exergy efficiency values were calculated as 14.4%, 13.4% and 11.3%, for TSAHP, FSAHP and ASHP heating systems, respectively. Levelized cost of heating of novel type system (TSAHP) ($/kWh) was 11.8% lower than conventional ASHP.
Solid-state fermented Omar’s was dried using microwave vacuum drying (MVD) and infrared freeze-drying (IFD). Hot air drying (AD) and traditional vacuum freeze-drying (FD) were used as controls. The effects of different drying methods on the drying kinetics, physicochemical properties (such as water retention capacity, oil retention capacity, swelling capacity, solubility, color), bioactive compounds (total phenols, soybean isoflavones, antioxidant activity) and flavor of solid-state fermented okara were studied. The results show that compared with AD, MVD required 86.2% less drying time and 62.2% lower energy while the fermented okara powder produced by MVD had better physicochemical properties and higher content of bioactive compounds. In terms of physicochemical and functional properties, IFD was close to FD, but it reduced drying time by 13.9% and energy consumption by 29.4%. As for flavor, MVD and IFD products were closer to fresh solid-state fermented okara.
To realize high-value utilization of discarded apple peel, this study investigated the effects of three selected commercial drying methods on drying kinetics, microstructure, color, phenolic stability and antioxidant capacity of apple peel. Apple peel was dehydrated by hot air drying (AD) at 75, 65 and 55 °C, heat pump drying (HP) at 65, 55 and 45 °C, and vacuum freeze-drying (FD), respectively. The results showed that HP was superior to AD and FD in terms of drying rate. In addition, HP at 65 °C provided high-quality dried apple peel due to less browning and brighter appearance, the highest retention of total phenolics (29.35 mg/g) and the strongest antioxidant activities, with the highest ABTS and FRAP value of 127.15 and 219.57 μmol TE/g, respectively. The content of the six major individual phenolics, i.e. caffeic acid, (-)-epicatechin, hyperoside, rutin, phlorizin and quercitrin, were found to be the highest in HP dried samples. Interestingly, the content of rutin was even increased after HP compared to the fresh sample. Considering drying efficiency, organoleptic quality and phenolic stability of the products, HP at 65 °C is suggested for drying of apple peel.
‘Murtilla’ (Ugni molinae Turcz) is a native Chilean species that belongs to the Myrtaceae family. It produces a small, globular fruit with pleasant flavor and recognized antioxidant activity. Convective hot-air and freeze drying are important techniques for fruit preservation, but their effect on murtilla fruit polyphenols and antioxidant activity has not yet been studied simultaneously. The objective of this study was to compare the effect of convective hot-air drying at 65 and 80 ºC and freeze drying on total polyphenol content (TPC), total anthocyanin content (TAC), polyphenols and anthocyanins of the Red Pearl-INIA variety of fresh murtilla fruits as measured by HPLC and antioxidant activity (DPPH and ABTS). The freeze dried fruit retained higher values for TPC (2192.4 mg/100 g d.w.), TAC (13.4 mg/100 g d.w.), polyphenols (79.02 mg/100 g d.w. by HPLC) and anthocyanins (0.188 mg/100 g d.w. by HPLC) than the murtilla dried by convective hot-air at both 65 and 80 ºC. The application of all treatments showed a positive increase in the DPPH (2945.4 to 3677.6 ?mol TE/100 g d.w.) and ABTS (2664.8 to 3397.2 ?mol TE/100 g d.w.) antioxidant activity of the dried murtilla compared to the DPPH (2111.1 ?mol TE/100 g d.w.) and ABTS (2247.8 ?mol TE/100 g d.w.) of the fresh fruit. Freeze drying was the best technique for the retention of polyphenols and antioxidant activity from the fresh murtilla fruit. Therefore, freeze drying is recommended over convective hot-air drying at 65 and 80 ºC when these bioactive compounds need to be preserved.
The study investigated the effect of different pretreatments of citric acid (CA), potassium metabisulphite (KMS), and ethylenediamine Tetraacetic acid (EDTA) on the drying characteristics and chemical composition of garlic slices in a convective hot air dryer at drying temperatures of 45, 50 and 55 o C. From the results obtained, the moisture diffusivity coefficients varied from 6.84×10-8 to 10.10×10-8 m 2 /s, 5.47×10-8 to 10.9×10-8 m 2 /s, 5.47×10-8 to 15.0×10-8 m 2 /s, and 6.84×10-8 to 9.94×10-8 m 2 /s, for the control and the various garlic slices pretreated with CA, KMS, and EDTA respectively. EDTA pretreated garlic slices chelated more metal ions in the garlic than the other pretreatments and resulted in a significant decrease in ash content from 2.66% to 2.02% in the fresh and dried garlic slices respectively at 55 o C. The allicin content of the EDTA pretreated samples increased significantly from 22.6 to 24.2µg/mL as drying air temperature increased from 45 to 55 o C. However, the KMS pretreated dried garlic slices showed the greatest brightness (85.95) in colour compared with the fresh (61.86), whereas the EDTA pretreated samples were yellower (17.43) than the others. On the other hand, the control dried garlic slices were harder (64.5N) than all the pretreated samples. Overall, KMS pretreated samples performed better in terms of moisture diffusivity, ash and allicin content, colour and texture at all drying temperatures investigated.
Murta (Ugni molinae Turcz) berries were dried under convective and combined convective-infrared conditions at 40, 50 and 60°C and 400–800 W in order to determine the drying characteristics and to compare the dried product's quality. To model the drying kinetics, seven mathematical equations were fitted to experimental data. According to statistical tests performed, the Midilli-Kuçuk model best fitted experimental data and was closely followed by the logarithmic model. Effective moisture diffusivity also showed dependency on drying conditions and varied between 7.59 × 10−10 to 44.18 × 10−10 m2/s and 11.34 × 10−10 to 85.41 × 10−10 m2/s for air-convective drying and combined infrared-convective drying. As to quality attributes of the berries, total surface color difference (ΔE) and total phenolic content (TPC) were determined. It was found that chromaticity coefficients a* and b* changed significantly, showing ΔE to be dependent on the mode of heat supply. TPC under all drying conditions decreased and was significantly different from the initial value in fresh samples. However, at a constant drying temperature, an increase in infrared power enhanced retention of TPC in samples. In particular, working at 40°C/800 W resulted in dried samples with the highest TPC.
The aims of this work were to determine the desorption isotherms of "Maltaise" orange peel and leaves and to investigate the effect of the infrared drying on the drying kinetics and on the physical and functional properties. The moisture desorption curves showed a sigmod shape (type II on the BET classification). GAB was found to be the best model for describing the desorption curves. The infrared drying rate increased, with temperature increasing at the same moisture ratio. High drying temperatures preserved initial color parameter values of "Maltaise" orange peels (from 21.893 ± 0.629 to 24.793 ± 0.525, from 37.973 ± 0.941 to 45.44 ± 0.390 and from 45.350 ± 1.077 to 50.439 ± 0.740 for a*, b* and C, respectively) and leaves (from-5.98 ± 1.651 to-5.276 ± 0.342, from 10.73 ± 1.547 to 16.42 ± 0.174 and from 12.283 ± 2.263 to 17.247 ± 0.384 for a, b* and C, respectively) and maximal phenolic content. Nevertheless, water and oil holding capacities decreased significantly. Low temperatures gave the best functional properties.
The objective of this study was to evaluate the application of: (1) freeze drying, (2) convective drying (50, 60, or 70 °C), (3) vacuum–microwave drying (240, 360, or 480 W), and (4) a combined method of convective pre-drying and vacuum–microwave finish drying in the processing of pomegranate arils and rind. The quality parameters under study included sugars and organic acids, punicalagins and ellagic acid, total polyphenols, total antioxidant activity, and sensory quality. In general, drying led to a reduction in all studied parameters; however, the behavior of arils and rind was different. Vacuum–microwave drying at 240 or 360 W was the best drying treatment for arils, while rind required freeze drying or soft conditions of convective drying (50 °C). Further research is needed to obtain proper results with convective pre-drying and vacuum–microwave finish drying of arils and rind. With proper selection of the drying protocol, high-quality dried arils will be available for consumers; these arils will be characterized by high contents of fructose (25 g 100 g−1), phytic acid (2.2 g 100 g−1), punicalagins (0.57 mg g−1), total polyphenols (1.6 mg eq gallic acid g−1), high antioxidant capacity (0.6 mg eq Trolox g−1), and high intensities of garnet color, sweetness, sourness, and fresh pomegranate aroma. Besides, dried rind with very high contents of active compounds (123 mg g−1 of punicalagins and 108 mg eq gallic acid g−1) and high antioxidant capacity (26 mg eq Trolox g−1) will be also available as functional material.
Garlic slices were dehydrated by convective drying (CD) and by a combined method consisting of convective pre-drying followed by vacuum-microwave finishing drying (CPD-VMFD). Drying of garlic using VMFD led to samples with high values of lightness and slightly lower values of the coordinates a* and b*. The treatment CPD-VMFD significantly decreased the drying time from 630 min for CD to 49 min and contributed to an important energy saving compared with CD (54.4–86.3 %). The total drying time was shorter when vacuum microwaves were introduced earlier and microwave power was higher. The highest temperature (114 °C) was found for samples pre-dried to a moisture content of 60 % and then dried at 360 W while showing the lowest energy consumption (98 ± 1 kJ g−1). In general, the total antioxidant capacity increased after drying of garlic slices; however, the content of total phenolic compounds showed the opposite trend, and thus other compounds, such as allicin, should be involved in the antioxidant capacity of dried garlic. Garlic slices were CP dried until 30 % of moisture content followed by VMFD at 240 or 360 W showed the best results in terms of energy consumption and antioxidant capacity.
Convective hot air-drying and freeze-drying were investigated as potential processes to preserve and concentrate allicin in garlic. Both temperature and air velocity had an important effect on hot air-drying kinetics. Sample size and temperature significantly affected the duration of freeze-drying, and thus the remaining moisture content of the garlic samples. Allicin content decreased with an increase of drying temperature in both convective hot air-drying or freeze-drying. Moderate air temperatures (40 and 50°C) allowed a better allicin retention than higher temperatures (60°C). However, retention of allicin was more important in garlic samples freeze-dried at a temperature of 20°C. The drying method did not show a significant impact on glass transition temperature values, indicating that garlic composition is a more important factor than internal structure. The predictions of the Gordon and Taylor model are in good agreement with the experimental data.
Garlic (Allium sativum) has been cultivated for centuries all over the world on account of its culinary and medicinal properties. The present work has been carried out with the emphasis on selection of an efficient and cost-effective drying technique for garlic with highest allicin retention. For comparative study, drying of garlic samples were experimented with using different methods, namely heat pump dryer, hot air dryer, solar cabinet dryer, infra red dryer, vacuum dryer, freeze dryer, and fluidized bed dryer having different operating conditions. A comparison of the efficiency of various drying methods was based on the parameters, e.g., drying kinetics, allicin content, and color analysis. In addition, the effect of garlic slice thickness on the above-mentioned parameters was also studied. Drying of garlic shows a typical falling rate period in sliced form. It was observed that dried garlic samples using heat pump drying, vacuum drying, freeze drying, and heat pump cum fluidized bed drying showed lesser color change and excellent allicin retention compared to the other methods.
Effect of air temperature on drying kinetics, vitamin C, antioxidant capacity, total phenolic content (TPC), colour due to
non-enzymatic browning (NEB) and firmness during drying of blueberries was studied. Drying curves were satisfactorily simulated
with the Weibull model at 50, 60, 70, 80 and 90°C. The scale parameter (β) decreased as air temperature increased and an activation
energy value of 57.85kJmol−1 was found. Important losses of vitamin C were reported during drying for all the working temperatures (p < 0.05). Although TPC decreased as air-drying temperature increased (p < 0.05) in comparison to its initial value, the dehydration at high temperatures (e.g., 90°C) presented high values for these
antioxidant components. Discoloration due to NEB reaction was observed at all the working temperatures showing a maximum value
at 90°C (p < 0.05). The radical scavenging activity showed higher antioxidant activity at high temperatures (80 and 90°C) than at low
temperatures (50, 60 and 70°C) (p < 0.05). A tissue firmness reduction was observed with increasing temperature (p < 0.05).
KeywordsBlueberries-Drying kinetics-Polyphenols-Antioxidant activity-Vitamin C-Firmness
The antioxidant activities of polar fractions of mature garlic bulbs and immature plants in four different model systems are presented. Antioxidant activity was evaluated as free radical-scavenging capacity (RSC), together with the effect on lipid peroxidation (LP). RSC was assessed by measuring the scavenging activity of garlic extracts on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide. Effects on LP were evaluated by following the activities of examined garlic extracts in Fe2+/ascorbate and Fe2+/H2O2 systems of induction. Investigated extracts reduced the DPPH radical formation (IC50 ranging from 1.03 to 6.01 mg/ml) and neutralised H2O2 (IC50 ranging from 0.55 to 2.01 mg/ml) in a dose-dependent manner. Strong inhibition of LP in both systems of induction was observed for all tested garlic extracts. Various levels of phenolics (0.05–0.98 mg gallic acid equivalents/g of dry extract) and flavonoid aglycones (4.16–6.99 μg quercetin equivalents/g of dry extract) in the investigated extracts of garlic could explain the obtained differences in these results only partially.
Anti-oxidant activity was measured for a Pinus radiata bark extract (bark 1), a Pinus maritima bark extract (bark 2), two grape seed extracts, three grape skin extracts, catechin, trolox, ascorbic acid (vitamin C) and calcium ascorbate. The activity was analyzed as ability to scavenge superoxide radicals in a hypoxanthine-xanthine oxidase system, using NBT and WST-1 assays. The 50% inhibition (IC50) of formazan formation was estimated for the samples studied. This study demonstrated that, in basic solution, bark extracts were 13 times more effective antioxidants than vitamin C; however, in aqueous and acidic solutions, bark1 acted as a more potent antioxidant than the other antioxidants in the NBT assay. Grape seed extracts 1 and 2 acted as moderate antioxidants in aqueous and basic solutions in both NBT and WST-1 assays and, in most cases, were three times as efficient as vitamin C. Activities of grape skin extracts were in the same range as trolox, being about 10 times lower than that of the bark extracts. Statistical analysis showed that there was no significant difference between the two assay methods or pH of the solution.
The double-blinded placebo-controlled randomized study has been performed in 51 coronary heart disease (CHD) patients to estimate the effects of time-released garlic powder tablets Allicor on the values of 10-year prognostic risk of acute myocardial infarction (fatal and non-fatal) and sudden death, with the respect of secondary CHD prevention. It has been demonstrated that 12-month treatment with Allicor results in the significant decrease of cardiovascular risk by 1.5-fold in men (p < 0.05), and by 1.3-fold in women. The above results were equitable also in terms of relative risks. The main effect that played a role in cardiovascular risk reduction was the decrease in LDL cholesterol by 32.9 mg/dl in men (p < 0.05), and by 27.3 mg/dl in women. Thus, the most significant effects were observed in men, while in women the decrease of cardiovascular risk appeared as a trend that might be due presumably to the insufficient sample size. Since Allicor is the remedy of natural origin, it is safe with the respect to adverse effects and allows even perpetual administration that may be crucial for the secondary prevention of atherosclerotic diseases in CHD patients.
After far-infrared (FIR) radiation onto rice hull, a methanolic extract was prepared for the determination of antioxidant ability. After 30 min of FIR treatment, the radical scavenging activity and total phenol contents of rice hull extracts increased from 47.74 to 79.63% and from 0.12 to 0.19 mM, respectively, compared to control. Inhibition of lipid peroxidation in extracts was also increased from 41.07 to 47.96%. According to the GC-MS analysis, more phenolic compounds (p-coumaric acid, 3-vinyl-1-oxybenzene, p-hydroxybenzaldehyde, vanillin, p-hydroxybenzoic acid, and 4,7-dihydroxyvanillic acid) were detected in FIR-irradiated rice hull extract. These results indicated that FIR radiation onto rice hull could liberate and activate covalently bound phenolic compounds that have antioxidant activities.
Diet has been recognized as a corner stone in the management of diabetes mellitus. Spices are the common dietary adjuncts that contribute to the taste and flavour of foods. Besides, spices are also known to exert several beneficial physiological effects including the antidiabetic influence. This review considers all the available information from animal experimentation as well as clinical trials where spices, their extracts or their active principles were examined for treatment of diabetes. Among the spices, fenugreek seeds (Trigonella foenumgraecum), garlic (Allium sativum), onion (Allium cepa), and turmeric (Curcuma longa) have been experimentally documented to possess antidiabetic potential. In a limited number of studies, cumin seeds (Cuminum cyminum), ginger (Zingiber officinale), mustard (Brassica nigra), curry leaves (Murraya koenigii) and coriander (Coriandrum sativum) have been reported to be hypoglycaemic.
Garlic and garlic extracts, through their antioxidant activities, have been reported to provide protection against free radical damage in the body. This study investigated antioxidant properties of garlic compounds representing the four main chemical classes, alliin, allyl cysteine, allyl disulfide, and allicin, prepared by chemical synthesis or purification. Alliin scavenged superoxide, while allyl cysteine and allyl disulfide did not react with superoxide. Allicin suppressed the formation of superoxide by the xanthine/xanthine oxidase system, probably via a thiol exchange mechanism. Alliin, allyl cysteine, and allyl disulfide all scavenged hydroxyl radicals; the rate constants calculated based on deoxyribose competitive assay were 1.4-1.7 x 10(10), 2.1-2.2 x 10(9), and 0.7-1.5 x 10(10) M (1) second(1), respectively. Contrary to previous reports, allicin did not exhibit hydroxyl radical scavenging activity in this study. Alliin, allicin, and allyl cysteine did not prevent induced microsomal lipid peroxidation, but both alliin and allyl cysteine were hydroxyl scavengers, and allyl disulfide was a lipid peroxidation terminator. In summary, our findings indicated that allyl disulfide, alliin, allicin, and allyl cysteine exhibit different patterns of antioxidant activities as protective compounds against free radical damage.
Tributyltin (TBT) can be transported to the human body by contaminated seafood. Presently, there is no known effective strategy to eliminate TBT's toxic effects from contaminated food. The present study was conducted to investigate the ability of garlic oil (GO) to prevent TBT-induced oxidative damage in vivo as well as in vitro. The results follow: both reactive oxygen species (ROS) production and malondialdehyde content decreased in mice pretreated with GO, the number of cells with damaged DNA in unprotected mice increased significantly compared with that in GO-protected mice (comet assay), and the alleviation of the depletion of cortical thymocytes and damage to nucleoli and mitochondria in GO-protected mice was observed. In human FL (human amniotic cells; American Type Culture Collection) cell studies, TBT-induced intracellular ROS generation was significantly inhibited after FL cells were pretreated with GO, and the TBT-induced cytotoxic effects were also prevented by GO. The results led to the first observation that GO was effective in reducing TBT-induced oxidative damage both in vivo and in vitro. The possible protective mechanism may stem from the considerable ability of GO to scavenge ROS. We conclude that GO could be an effective agent or food supplement in reducing the toxicity of TBT.
A method for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants. The pre-formed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+) is generated by oxidation of ABTS with potassium persulfate and is reduced in the presence of such hydrogen-donating antioxidants. The influences of both the concentration of antioxidant and duration of reaction on the inhibition of the radical cation absorption are taken into account when determining the antioxidant activity. This assay clearly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the chemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxidant test systems, rather than the generation of the radical taking place continually in the presence of the antioxidant. Hence the results obtained with the improved system may not always be directly comparable with those obtained using the original TEAC assay. Third, it is applicable to both aqueous and lipophilic systems.
Hot air (HA) drying of banana has low drying efficiency and results in undesirable product quality. The objectives of this research were to investigate the feasibility of infrared (IR) heating to improve banana drying rate, evaluate quality of the dried product, and establish models for predicting drying characteristics. Banana slices of 5 mm and 8 mm thickness were dried with IR and HA at product temperatures of 60°C, 70°C and 80°C. Banana drying characteristics and changes in residual polyphenol oxidase (PPO), Hydroxymethylfurfural (HMF), color, moisture content (MC) and water activity during the treatments were investigated. Results showed that significant moisture reduction and higher drying rates were achieved with IR drying compared to HA drying in the early stage. The drying data could be fitted to the Page model for accurate prediction of MC change for IR and HA drying with mean R2 of 0.983. It was noted that enzyme inactivation occurred more quickly with IR than with HA drying. A unique response of PPO under IR and HA drying was revealed. IR heating of banana inactivated PPO within the first 20 min of drying at 60°C, 70°C and 80°C, while PPO was first activated before inactivation at 60°C and 70°C drying with HA. The highest HMF content occurred in banana slices with 5 mm thickness dried with IR at a product temperature of 80°C. It is therefore recommendable to dry banana with IR at product temperature of 70°C or below to preserve the product quality. These findings are new and provide more insight in the application of IR heating for drying banana for improved drying rate and product quality.
The effect of different infrared power levels on the drying kinetics of button mushrooms was investigated. Mushroom slices were dried at infrared power levels of 83, 125, 167, and 209 W. The power level affected the drying and rehydration characteristics of mushroom slices. Drying time was reduced from 300 min to 40 min as the infrared power level increased from 83 to 209W. Mathematical models frequently used to represent drying of agricultural products were fitted to experimental data of mushroom drying. The parabolic model was the best for representation of mushroom drying. Effective moisture diffusivity varied from 3.81×10−10 to 4.20×10−9 m2/s over the infrared power levels used. The activation energy was estimated using a modified Arrhenius-type equation and calculated to be 7.55 kW/kg.
The apple peel, a by-product of apple processing, has a high total phenolic content (TPC); however, these compounds can be highly thermosensitive and unstable. Therefore, the aim of this study was to determine the degradation kinetics of the TPC in apple peels during drum-drying as a stabilization and recovery method. Apple peels (Granny Smith) were dried at 110, 120, 130 or 140 °C for 250 s with a constant drum clearance (0.2 mm). TPC degradation exhibited first-order kinetics and their retentions at the end of the process were 73.13% at 110 °C, 57.28% at 120 °C, 43.40% at 130 °C and 21.10% at 140 °C. Finally, empirical models were significantly fitted to predict the TPC as the apple peels reached a certain level of dehydration, which may be useful from the processing standpoint and validate the use of drum-drying as a process tool for the recovery of apple industrial wastes.
The effect of different infrared power levels on the drying kinetics and rehydration capacity of tomato slices was investigated. The tomatoes were cut into eighths and dried at different infrared power levels. It was observed that the power levels affected the drying time and rehydration capacity. Drying time was reduced from 450 to 240 min as the infrared power level increased from 125 to 188 W. The experimental data obtained from drying study were fit with nine mathematical models to evaluate the drying kinetics of tomato slices. The fit quality of the proposed models was evaluated using the determination of coefficient, mean relative percent error, reduced chi‐square and root mean square error. Among the nine drying models, the model of Midilli et al. showed the best fit of drying kinetics of tomato slices. Effective moisture diffusivity varied from 2.66 to 5.17 × 10−9 m2/s and was significantly influenced by infrared power.
The degradation kinetics of thiosulfinates and the reduction of antioxidant activity of garlic bulbs cut in slices were studied during steam at 100 °C and in water at 80 and 90 °C. Blanching process led to significant reduction of the antioxidant activity and thiosulfinate contents. The reaction rate constants for loss of thiosulfinate species and antioxidant activity increased with blanching temperature, with activation energies of 7.67 and 89.75 kJ/mol, respectively. The antioxidant activity showed a significant correlation with thiosulfinates (R = 0.7604), and both the antioxidant activity and thiosulfinate contents decreased with increasing blanching time. The antioxidant activity did not show significant differences after 6 min of steam blanching and 8 min of water blanching at 90 and 80 °C. Regarding the thiosulfinate concentration, there was no significant difference after 8 min of blanching for all temperatures.
This study was conducted to evaluate quality and structural changes in parallelepipedic pieces of pears during convective drying at different air temperatures (30–70 °C).Submitted to atmospheric O2 conditions, ascorbic acid deterioration demonstrated first-order kinetic behaviour and was found to depend on air temperature and pear moisture content. Loss of ascorbic acid content increased with increasing air temperature. Possible explanation could be the irreversible oxidative reaction occurring during drying. Phenol content degradation fitted a pseudo first-order reaction and was significantly influenced by air temperature.Variations in bulk density, shrinkage and porosity essentially depended on changes in moisture content. Porosity exhibited a nonlinear variation with respect to moisture content. Volume change showed, as expected, a linear variation with moisture content. Drying temperature significantly induced the increase of a* and b* colorimetric parameters due to non-enzymatic browning reaction, which turned the samples more reddish and yellow when the temperature rose.
Laboratory dryer was designed in such a way that drying could be done either with infrared energy or by convection. It was equipped with near-infrared radiators with peak wavelength at 1200 nm. The energy efficiency of the infrared dryer was between 35% and 45%. Apple slices were dried with infrared energy and by convection under equivalent conditions. Kinetics of infrared drying was dependent on the distance between emitters and the heat-irradiated surface and air velocity. Drying kinetics was inversely proportional to both the distance and the air velocity. It was found that both surfaces of apple slice participate in water evaporation. However, the heat-irradiated surface evaporates much more water than that not heated by infrared energy until 80% of water is removed from the material. At the final stages of drying, there is no difference between upper and bottom surfaces of the apple slice as far as the flux of evaporated water is concerned.Comparison of infrared drying with convective drying done at equivalent parameters showed that time of the process can be shortened by up to 50% when heating is done with infrared energy.
Garlic powder with high allicin content was prepared using microwave–vacuum and vacuum drying as well as microencapsulation in order to protect alliinase activity throughout the human stomach and improve the ratio of alliin transforming into allicin. The results showed that the optimal microwave–vacuum drying condition was drying for 3min under the microwave output power 376.1W, then 282.1W for 3min, followed by 188.0W for 9min, and finally for 3min under the output power 94.0W. The thiosulfinates retention after drying was 90.2%. Following drying, garlic powder was microencapsulated by modified fluidized bed technique. Scanning electron microscope revealed good integrity and core materials that were embedded in microcapsules. Studies on the release kinetics of microencapsulated garlic granulates in vitro using simulated intestinal fluid indicated that release of garlic powder could be controlled in intestine by passing through human stomach conditions.
Allinase, which catalyzes the conversion of alliin to allicin, the principal component of potential medicinal value in garlic, is a thermo-labile enzyme. The potential for allicin formation is determined by the quantity of allinase that remains active after the process of preserving garlic by drying. The kinetics of enzymatic activity loss during drying by temperature cycling or by constant temperature were evaluated and compared. Allicin-forming potential was 91% preserved by temperature cycling from 40 to 60°C. It was found that sugars present in the garlic and the high molecular mass of the enzyme were responsible for protection against degradation at high drying temperatures. Preservation of the enzymatic activity under cyclical conditions occurred mainly with exposure to low temperatures for drying periods longer than those of constant drying conditions.
There are many active functional compounds in citrus peels, such as flavonoid and phenolic acid. Scientists tried to obtain more bioactive components from citrus peels by various methods. This research investigated the effects of different drying temperatures (50, 60, 70, 80, 90 and 100 °C) on changes in the flavonoid, phenolic acid and antioxidative activities of citrus fruit (Citrus sinensis (L.) Osbeck) peels. The total phenolic and flavonoid contents of drying treated orange peels were decreased by lower drying temperature (50 and 60 °C) and increased by higher drying temperature (70, 80, 90 and 100 °C). Amounts of phenolic compounds in the 100 °C treated sample extract were significantly higher than the amounts in the samples heated at other temperatures (P < 0.05). EC50 values of orange peel extracts by DPPH radical scavenging effects and ABTS·+ scavenging effects were increased with lower drying temperature and decreased with higher drying temperature, and the values of 100 °C treated sample extract were significantly lower than the samples heated at other temperatures (P < 0.05). However, the chelating Fe2 + activities of samples showed the opposite trend.
Freeze-drying and hot air-drying were applied in the preparation of pumpkin flours to investigate the effects of drying methods on the antioxidant activities and physicochemical properties. The antioxidant activities of methanol extracts from pumpkin flours were studied in terms of total antioxidant activity, reducing power, free radical scavenging, superoxide anion radical scavenging and metal chelating activities. Hot air-dried pumpkin flour showed stronger antioxidant activities than freeze-dried flour. The percentage inhibition of peroxidation in linoleic acid system by 15 mg mL−1 extracts from hot air-dried and freeze-dried pumpkin flours was found to be 92.4% and 86.1% after 120 h of incubation, respectively. Hot air-dried pumpkin flour exhibited higher reducing power, free radical scavenging and metal chelating activities than freeze-dried flour. This study also indicated that freeze-drying significantly reduced the browning and preserved the redness of pumpkin flours. Hot air-drying reduced the oil absorption capacity, water absorption and porosity of pumpkin flours, while it markedly increased the water solubility and bulk density.
The effect of air-drying parameters on antioxidant activity and changes in antioxidant compounds of broccoli (Brassica oleracea L.) were studied. Broccoli samples were dried to 70 g kg−1 moisture content using temperatures ranging from 50 to 100 °C and air flow-rates from 1.20 to 2.25 m s−1, resulting in drying times from 25 to 90 min. Temperature, owing to its positive effect on the oxidation kinetics, was negatively correlated with ascorbic acid and free and total polyphenol contents but not with kaempferol, even though the sample dried at the highest temperature showed the lowest kaempferol content. The air flow-rate was positively correlated with the total (TPP) and free (FPP) polyphenol contents because it led to a reduction in the drying time. No correlation was found between air flow-rate and kaempferol content. Air flow-rate and temperature positively affected the antioxidant activity by reducing the drying time. High-temperature, short-time processes maximised the antioxidant activity of broccoli owing to the negative effect of drying time on antioxidant activity. The antioxidant activity of broccoli was positively and significantly correlated with the FPP content but not with TPP and kaempferol. The evaluation of hydroxymethylfurfural content as an indicator of the occurrence of a Maillard reaction in dried broccoli did not support the hypothesis of a contribution of MRPs to the antioxidant activity of dried broccoli. Copyright © 2006 Society of Chemical Industry
The influence of far-infrared (FIR) irradiation in multi-stage paddy drying process on moisture reduction and milling quality has been experimentally studied. The process, running in series, comprised fluidized bed drying, FIR irradiation, tempering and ambient air ventilation. The experimental results showed that the critical moisture content after the fluidized bed drying was around 23% d.b. whereas incorporating with the FIR irradiation could continuously reduced the moisture content to 21% d.b. without affecting paddy head rice yield and whiteness. Under the intensity of FIR irradiation, wet paddy was more sensitive than dry paddy. However, to maintain head rice yield, moisture equalization by a subsequent tempering stage was still required. Studying the microstructure of rice kernels and the pasting behavior of rice flours showed the presence of partial gelatinization resulted in the improvement of head rice yield.
Hot air, microwave and hot air-microwave drying characteristics of kiwifruits (5X03 AE 0X236 mm thick) were investigated. Drying rates, shrinkage and rehydration capacities of these drying regimes were compared. The drying took place in the falling rate drying period regardless of the drying method. Drying with microwave energy or assisting hot air drying with microwave energy resulted in increased drying rates and substantial shortening of the drying time. Shrinkage of kiwifruits during microwave drying was greater than hot air drying. Less shrinkage was observed at hot air-microwave drying. Microwave dried kiwifruit slices exhibited lower rehydration capacity and faster water absorption rate than the other drying methods studied.
The effects of air temperature, air velocity, and pretreatments (blanching, sulphiting, and sodium chloride dipping) on drying kinetics of green- and red-pepper slices were investigated. Drying experiments were performed in a fluidized bed dryer. In the falling rate period, moisture transfer from peppers was described by applying the unsteady state Fickian diffusion model, and the apparent moisture diffusion coefficients (Da) were calculated. The effect of temperature on Da could be interpreted according to Arrhenius law. Drying rate and therefore Da values were found to be affected by pretreatments. Rehydration rates of dried peppers at 25 and 45 °C were also determined and found to be independent of drying conditions and rehydration temperature. Predrying treatments were found to improve partly the rehydration characteristics of peppers.
Red pepper has been recognised as an excellent source of antioxidants, being rich in ascorbic acid and other phytochemicals. Drying conditions, particularly temperature, leads to pepper modifications that can cause quality degradation. In this work, the effects of process temperatures between 50 and 90 °C on physico-chemical properties, rehydration, colour, texture, vitamin C, antioxidant capacity and total phenolics during the drying of red pepper were studied. The rehydration ratio decreased with temperature and the maximum water holding capacity was achieved at 50 °C. Both vitamin C content and the total phenolic content decreased as air-drying temperature decreased. The radical scavenging activity showed higher antioxidant activity at high temperatures (i.e. 80 and 90 °C) rather than at low temperatures (i.e. 50, 60 and 70 °C). Chromatic parameters (L*, a*, b*, C* and H°), non-enzymatic browning compounds and extractable colour were affected by drying temperature, which contributed to the discolouring of pepper during this process.
The effect of drying temperature on drying rates of apple slice was examined at different temperature. The values of drying rate almost doubled when the drying temperature was increased from 50 to 80 °C. The experimental drying data were applied to various drying equation (Newton, Page, Modified Page, Wang and Singh, Henderson and Pabis, Logarithmic, Diffusion approach, Simlified Fick’s diffusion SFFD equation, Modified Page equation-II and Midilli equation). Midilli equation was best for characterizing drying behavior of apple for the whole range of temperature. The variation of these models parameters with temperature were described as Arrhenius and logarithmic type function of drying temperature. Sixty-six different model equations that describing the temperature and time dependence of infrared drying of apple were derived. Theoretical models describing temperature and time dependence of drying were fitted to experimental data and model parameters in equations were determined by multiple regression analysis in temperature range 50–80 °C. Model 50 derived from Modifiye Page II has lowest RMSE, MBE and chi-square and the highest modeling efficiency and regression coefficient. The moisture ratio change during infrared drying (0–240 min) of apple in the temperature range of 50–80 °C can be predicted by single equation:MR=exp(-(-9.08244+1.580765ln(T))(t/(-0.628792+0.574354ln(T))2)(11.49544-1.74016ln(T))).
The effect of air temperature on the physicochemical and nutritional properties and antioxidant capacity of Aloe vera (Aloe barbadensis Miller) gel was investigated. The following parameters were analysed: proximal composition, water activity (aw), pH, acidity, non-enzymatic browning, surface colour, vitamin content (C and E), mineral content, and antioxidant capacity. The drying kinetics of A. vera gel was modelled using the Wang–Singh equation, which provided a good fit for the experimental data. Analysis of variance revealed that the drying temperature exerted a clear influence on most of the quality parameters. A drying temperature of 80 and 90 °C resulted in significant variation in and/or loss of the physicochemical and nutritional properties of the gel; in addition, the antioxidant capacity of the gel was decreased at these temperatures. These effects were also observed as a result of a lengthy drying period (i.e., 810 min at 50 °C). However, minor alterations in the physicochemical and nutritional properties of A. vera gel were produced at drying temperatures of 60–70 °C, resulting in the production of a high quality gel.
Nutritional factors are widely considered to be critical for human health. Overwhelming evidence from epidemiological studies indicate that diets rich in fruit and vegetables are associated with a lower risk of several degenerative diseases. These results have created a new perspective concerning the potential of diet in preventing serious diseases in the future. However, the health-promoting capacity of fruit and vegetables strictly depends on their processing history. This aspect has been generally neglected or scarcely considered in present nutritional and epidemiological studies. Processing is expected to affect content, activity and bioavailability of bioactive compounds.The aim of this article, therefore, is to review the effects of processing on the antioxidant properties of foods by means of a multidisciplinary approach. It is believed that the implications of this challenging and rapidly advancing area may contribute to enhanced industrial competitiveness as well as consumer health and well-being.
Olive cake is a sub-product of the mechanical olive oil extraction industry, which consists of pit and pulp of the olive fruit, olive oil and vegetable water. It has been using for direct combustion in bakeries and olive oil mills due to its energy content. However, the initial moisture content of olive cake is approximately 44.78% ± 0.5 (wet basis), and this has to be reduced to about 5% to recover its energy content. Therefore, the characterization of the thin layer drying kinetics was investigated at a wide range of drying temperatures (50–110 °C), a constant sample thickness and air velocity of 1.2 ± 0.03 m/s at a laboratory scale dryer. Various mathematical models simulated drying curves of olive cake. The logarithmic model was found to give better predictions than the others. In addition, the temperature dependence of the effective diffusivity coefficient was expressed by an Arrhenius type relationship. The effective diffusivity varied between 0.3 and 1.1 × 10−8 m2/s with an activation energy of 17.97 kJ/mol.
The effect of heat treatment on the changes in the overall antioxidant activity and polyphenolic compounds of Shiitake extract was investigated. Raw Shiitake was heated at 100 and 121 °C for 15 or 30 min using an autoclave. After heat treatment, the free and bound polyphenolics and flavonoids in the mushroom extracts were analyzed. 2,2-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities were measured to evaluate antioxidant activity of the extracts. The polyphenolic contents and antioxidant activities in the extracts increased as heating temperature and time increased. For example, the free polyphenolic content in the extract heated at 121 °C for 30 min was increased by 1.9-fold compared to that in the extract from the raw sample. The ABTS and DPPH radical scavenging activities were increased by 2.0-fold and 2.2-fold compared to the raw sample, respectively. There was a good correlation between total polyphenolic contents and AEAC (p < 0.001). Results showed that heat treatment significantly enhanced the overall antioxidant activities of Shiitake mushroom.
A laboratory scale infrared-convective dryer was developed and single layer drying of onion slices was carried out at infrared power levels of 300, 400 and 500 W, drying air temperatures of 35, 40 and 45 °C and inlet drying air velocities of 1.0, 1.25 and 1.5 m/s. The drying time reduced by about 2.25 times on increasing infrared power from 300 to 500 W, air temperature 35–45 °C and air velocity from 1.0 to 1.5 m/s. Effective moisture diffusivity varied from 0.21 × 10−10 to 1.57 × 10−10 m2/s and was significantly influenced by infrared power and air temperature.. The rehydration ratio of dehydrated onion slices was found to be in the range of 4.5 and 5.3.
The objective of this study was to evaluate the application of vacuum-microwave drying (240, 360, and 480 W) in the production process of dehydrated strawberry and to compare and contrast the quality of these dehydrated strawberries in terms of their polyphenol compounds, concentration of some heat liable components, and color to that of freeze-dried, convective, and vacuum-dried strawberry. Thus, the effect of vacuum-microwave drying and other drying methods on the antioxidant activity of berries was evaluated. Whole fresh and dried fruits were assessed for phenolics (anthocyanins, flavanols, hydroxycinnamic acids, and flavonols), ascorbic acid, and antioxidant activity (all parameters were calculated on a dry matter basis). Analysis of data shows that ellagic acid and flavanol changes were affected by drying techniques and cultivar. Drying destroyed anthocyanins, flavanols, and ascorbic acid, and there was a significant decrease in antioxidant activity. The most striking result was that conventional and vacuum drying decreased antioxidant activity in both cultivars, whereas contradictory results were found for vacuum-microwave processed strawberry. This study has demonstrated that vacuum-microwave drying, especially at 240 W, can produce high-quality products, with the additional advantage of reduced processing times, compared to other processes such as freeze-drying.
Many recent studies have implicated dietary factors in the cause and prevention of important diseases, including cancer, coronary heart disease, birth defects, and cataracts. There is strong evidence that vegetables and fruits protect against these diseases; however, the active constituents are incompletely identified. Whether fat per se is a major cause of disease is a question still under debate, although saturated and partially hydrogenated fats probably increase the risk of coronary heart disease. One clear conclusion from existing epidemiologic evidence is that many individuals in the United States have suboptimal diets and that the potential for disease prevention by improved nutrition is substantial.
A simple, automated test measuring the ferric reducing ability of plasma, the FRAP assay, is presented as a novel method for assessing "antioxidant power." Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions in known concentration. Absorbance changes are linear over a wide concentration range with antioxidant mixtures, including plasma, and with solutions containing one antioxidant in purified form. There is no apparent interaction between antioxidants. Measured stoichiometric factors of Trolox, alpha-tocopherol, ascorbic acid, and uric acid are all 2.0; that of bilirubin is 4.0. Activity of albumin is very low. Within- and between-run CVs are <1.0 and <3.0%, respectively, at 100-1000 micromol/liter. FRAP values of fresh plasma of healthy Chinese adults: 612-1634 micromol/liter (mean, 1017; SD, 206; n = 141). The FRAP assay is inexpensive, reagents are simple to prepare, results are highly reproducible, and the procedure is straightforward and speedy. The FRAP assay offers a putative index of antioxidant, or reducing, potential of biological fluids within the technological reach of every laboratory and researcher interested in oxidative stress and its effects.
A method for the screening of antioxidant activity is reported as a decolorization assay applicable to both lipophilic and hydrophilic antioxidants, including flavonoids, hydroxycinnamates, carotenoids, and plasma antioxidants. The pre-formed radical monocation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*+) is generated by oxidation of ABTS with potassium persulfate and is reduced in the presence of such hydrogen-donating antioxidants. The influences of both the concentration of antioxidant and duration of reaction on the inhibition of the radical cation absorption are taken into account when determining the antioxidant activity. This assay clearly improves the original TEAC assay (the ferryl myoglobin/ABTS assay) for the determination of antioxidant activity in a number of ways. First, the chemistry involves the direct generation of the ABTS radical monocation with no involvement of an intermediary radical. Second, it is a decolorization assay; thus the radical cation is pre-formed prior to addition of antioxidant test systems, rather than the generation of the radical taking place continually in the presence of the antioxidant. Hence the results obtained with the improved system may not always be directly comparable with those obtained using the original TEAC assay. Third, it is applicable to both aqueous and lipophilic systems.
Oxidative modification of DNA, proteins and lipids by reactive oxygen species (ROS) plays a role in aging and disease, including cardiovascular, neurodegenerative and inflammatory diseases and cancer. Extracts of fresh garlic that are aged over a prolonged period to produce aged garlic extract (AGE) contain antioxidant phytochemicals that prevent oxidant damage. These include unique water-soluble organosulfur compounds, lipid-soluble organosulfur components and flavonoids, notably allixin and selenium. Long-term extraction of garlic (up to 20 mo) ages the extract, creating antioxidant properties by modifying unstable molecules with antioxidant activity, such as allicin, and increasing stable and highly bioavailable water-soluble organosulfur compounds, such as S-allylcysteine and S-allylmercaptocysteine. AGE exerts antioxidant action by scavenging ROS, enhancing the cellular antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase, and increasing glutathione in the cells. AGE inhibits lipid peroxidation, reducing ischemic/reperfusion damage and inhibiting oxidative modification of LDL, thus protecting endothelial cells from the injury by the oxidized molecules, which contributes to atherosclerosis. AGE inhibits the activation of the oxidant-induced transcription factor, nuclear factor (NF)-kappa B, which has clinical significance in human immunodeficiency virus gene expression and atherogenesis. AGE protects DNA against free radical--mediated damage and mutations, inhibits multistep carcinogenesis and defends against ionizing radiation and UV-induced damage, including protection against some forms of UV-induced immunosuppression. AGE may have a role in protecting against loss of brain function in aging and possess other antiaging effects, as suggested by its ability to increase cognitive functions, memory and longevity in a senescence-accelerated mouse model. AGE has been shown to protect against the cardiotoxic effects of doxorubicin, an antineoplastic agent used in cancer therapy and against liver toxicity caused by carbon tetrachloride (an industrial chemical) and acetaminophen, an analgesic. Substantial experimental evidence shows the ability of AGE to protect against oxidant-induced disease, acute damage from aging, radiation and chemical exposure, and long-term toxic damage. Although additional observations are warranted in humans, compelling evidence supports the beneficial health effects attributed to AGE, i.e., reducing the risk of cardiovascular disease, stroke, cancer and aging, including the oxidant-mediated brain cell damage that is implicated in Alzheimer's disease.
Processed fruits and vegetables have been long considered to have lower nutritional value than their fresh commodities due to the loss of vitamin C during processing. This research group found vitamin C in apples contributed < 0.4% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals. This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C. Here it is shown that thermal processing elevated total antioxidant activity and bioaccessible lycopene content in tomatoes and produced no significant changes in the total phenolics and total flavonoids content, although loss of vitamin C was observed. The raw tomato had 0.76 +/- 0.03 micromol of vitamin C/g of tomato. After 2, 15, and 30 min of heating at 88 degrees C, the vitamin C content significantly dropped to 0.68 +/- 0.02, 0.64 +/- 0.01, and 0.54 +/- 0.02 micromol of vitamin C/g of tomato, respectively (p < 0.01). The raw tomato had 2.01 +/- 0.04 mg of trans-lycopene/g of tomato. After 2, 15, and 30 min of heating at 88 degrees C, the trans-lycopene content had increased to 3.11+/- 0.04, 5.45 +/- 0.02, and 5.32 +/- 0.05 mg of trans-lycopene/g of tomato (p < 0.01). The antioxidant activity of raw tomatoes was 4.13 +/- 0.36 micromol of vitamin C equiv/g of tomato. With heat treatment at 88 degrees C for 2, 15, and 30 min, the total antioxidant activity significantly increased to 5.29 +/- 0.26, 5.53 +/- 0.24, and 6.70 +/- 0.25 micromol of vitamin C equiv/g of tomato, respectively (p < 0.01). There were no significant changes in either total phenolics or total flavonoids. These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risks of chronic diseases.
To determine the effects of fresh and freeze-dried extracts of Allium sativum on the physiology and morphology of Candida albicans.
Inhibition of growth in glucose-yeast extract-peptone was measured using a multiwell plate reader. Scanning and transmission electron microscopy investigations indicated loss of structural integrity. Gas chromatography-mass spectrometry of extracts was employed to separate and quantify putative inhibitory sulphur-containing components.
Fresh garlic extract has a greater efficacy than garlic powder extract as indicated both by its effects on morphology and inhibition of growth.
The ubiquitous opportunistic pathogen C. albicans is sensitive to garlic; resistance to the broad spectrum of active principles present is unlikely so that its anticandidal effects may provide an important alternative route to chemotherapy.
The inhibitory effect of garlic extract, diallyl sulphide and diallyl disulphide against methicillin-resistant Staphylococcus aureus (MRSA) infection in BALB/cA mice was studied. The influence of these agents upon the levels of fibronectin, interleukin-6 and lipid oxidation in MRSA-infected mice was examined.
Garlic extract at 100% and 50%; diallyl sulphide (DAS) at 10% and 5%; diallyl disulphide (DADS) at 1% and 0.5% were used in this study. Sixteen clinical MRSA isolates obtained from infected patients were used in this study (n=16). Mice were infected by injecting 200 microL MRSA-PBS solution, which contained 10(7) cfu, via the tail vein. At 16 h post-infection (p.i.), garlic extract, DAS or DADS at 200 microL was administrated orally. At 24 h p.i., mice were killed and blood, liver, kidney and spleen of each mouse were collected. Plasma and the filtrate from each organ and serial dilutions were used to determine colony count. Plasma fibronectin level was determined by rabbit anti-rat fibronectin antibody and quantified by ELISA. Interleukin-6 levels were determined by commercial kit. Lipid oxidation was determined by measuring malondialdehyde levels.
The oral administration of these agents significantly decreased the viability of MRSA, in plasma, liver, kidney and spleen (P<0.05). MRSA infection significantly increased fibronectin and interleukin-6 levels in plasma of MRSA-infected mice (P<0.05); however, the oral administration of garlic extract and two diallyl sulphides significantly reduced both fibronectin and interleukin-6 levels (P<0.05). MRSA infection also significantly enhanced lipid oxidation in plasma and three organs (P<0.05). The treatments of garlic extract and two diallyl sulphides significantly decreased the malondialdehyde level and showed antioxidant protection (P<0.05).
These data strongly supported the conclusion that garlic extract, diallyl sulphide and diallyl disulphide possessed multiple protective functions against MRSA infection, in which diallyl sulphide and diallyl disulphide could be considered as novel therapeutic agents for the treatment of MRSA infection.
Multidrug resistance (MDR) mediated by the overexpression of drug efflux protein P-glycoprotein (P-gp) is one of the major obstacles to successful cancer chemotherapy. P-gp acts as an energy-dependent drug efflux pump, reducing the intracellular concentration of structurally unrelated drugs. Modulators of P-gp function can restore the sensitivity of multidrug-resistant cells to such drugs. In the present study, we evaluated the P-gp modulatory potential of diallyl sulfide (DAS), a volatile organosulfur compound present in garlic, known to possess many medicinal properties, including antimutagenic and anticarcinogenic activities. For in vitro studies, K562 leukemic cells were made resistant (K562/R) to the cytotoxicity of vinblastine (VBL) by progressive adaptation of the sensitive K562 parental cells to VBL. Cross-resistance of K562/R was found between vincristine (VCR), doxorubicin and other antineoplastic agents. A non-toxic concentration of DAS (8.75 x 10(-3) M) enhanced the cytotoxic effects of VBL and another vinca alkaloid, VCR, time dependently in VBL-resistant human leukemia (K562/R10) cells but had no effect on the parent (K562/S) cells. The results show that DAS decreased the induced levels of P-gp in resistant cells back to the normal levels as analyzed both qualitatively and quantitatively by western blotting and immunocytochemistry. Furthermore, in vivo combination studies showed that DAS effectively inhibited vinca alkaloid-induced P-gp overexpression in mouse hepatocytes. Quantitation of immunostained tissue sections with image analysis showed that the reduction in P-gp levels was up to 73% for VBL- and 65% for VCR-induced drug resistance. The above features thus indicate that DAS can serve as a novel, non-toxic modulator of MDR and can be used as a dietary adjuvant.