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Changes of Radical Scavenging Activity and Polyphenols Content During Storage of Dried Apples
International Journal of Food Properties
Abstract
The aim of the present research was to analyze the influence of the heating method used during convection, microwave-convection, and infrared-convection drying of apple tissue on its polyphenols content and radical scavenging activity, as evaluated both directly after dry-ing and after a 12-month period of storage. In the course of drying, a decrease in radical scavenging activity and polyphenols content occurred. At the same time, changes in the for-mer parameter depended on the length of the drying process. The kinetics of the decrease were described by means of first-order reactions. Furthermore, radical scavenging capacity as well as polyphenols content significantly decreased during the storage.
... However, the preservation of these products is associated with significant losses of valuable antioxidants. Drying is the most popular method of preserving herbaceous plants; therefore, the search for the method and the parameters of drying leading to the preservation of antioxidant capacity is very important [46,48,49]. ...
... The results were expressed as EC 50 , i.e., the concentration of the leaf extract (fresh and dried) required to inhibit half of the initial amount of the radical. This means that lower EC 50 values indicate higher antiradical activity [17,41,46,48]. ...
... mg TE/g d.m. A decrease in radical scavenging activity during the drying of herbaceous plants was found in many works [2,14,[46][47][48]. ...
Moldavian dragonhead leaves are a valuable waste product from the production of seed oil, from a nutritional point of view. It has been shown that dried leaves can be used for the production of functional foods. Despite the wide possibilities of using dried Moldavian dragonhead leaves, research on the selection of drying methods is scarce. This particular study investigated the traditional convection and the hybrid microwave–convection methods to dry Moldavian dragonhead leaves. We showed that the convection method supported by microwaves allowed us to obtain dried leaves in a much shorter time than traditional convection drying (the convection drying lasted, depending on the parameters, 184-75 min, while the convection–microwave drying lasted 33-7 min). Moreover, the microwave–convection-dried leaves contained more polyphenols (the average TPC in the convection droughts was 29.532, while in the microwave–convection droughts, it was 41.880 mg GAE/g d.m.) and chlorophylls (an average of 2.326 in the convection-dried and 2.675 mg/g d.m. in the microwave–convection-dried material) and were characterized by significantly higher antioxidant activity, compared to convection-dried ones.
... Quality changes during the storage of dried food materials have been studied by many researchers (Nowacka et al., 2014;Rocha-Parra et al., 2016;Tavares et al., 2020;Tereucan et al., 2021;Tripetch & Borompichaichartkul, 2019). ...
... Storage conditions, such as packaging types, temperatures, % relative humidity levels as well as storage times, are known to play a major role in the changes. In addition, the types of storage conditions influence differently the quality changes of the dried materials (Nowacka et al., 2014;Rocha-Parra et al., 2016;Tavares et al., 2020;Tereucan et al., 2021;Tripetch & Borompichaichartkul, 2019). Therefore, studies of suitable storage conditions for each food material should be individually conducted. ...
... However, the key factor affecting the changes of both TFC and DPPH values was storage time. As can be seen, both values increased to their peak levels at 30 days of storage, which is caused by the emergence of new compounds such as the products from the Maillard reaction or enzymatic browning resulting in the increment of antioxidant activity (Nowacka et al., 2014). ...
A petal of red water lily is considered as a medicinal plant due to its various health benefits. However, it suffers from a short shelf life due to a high moisture content of its fresh form. So, moisture sorption isotherm is used to design drying and storage conditions for extending its shelf‐life. Up to now, there is no research on sorption isotherms and factors affecting the quality changes during storage of the dried petal. Therefore, this study aimed at fulfilling this research gap for designing or controlling drying process and storage condition. The GAB model well‐described sorption isotherms data and the monolayer moisture content ranged from 3.60 to 4.57% d.b. The Blahovec‐Yanniotis model provided the information of water contribution in adsorption and desorption processes. Storage time and relative humidity were the main factors affecting the quality changes during storage while storage temperature served as a facilitator for these changes.
... Total phenolic content (TPC): The total phenolic content was determined using Folin-Ciocalteau's method [45], in accordance with modified procedure presented previously [46,34]. The absorbance was measured at 750 nm against sample without extract (Hekios Thermo Electron v. 7.03 spectrophotometer). ...
... compounds in 100 g d.m. (dry matter), whereas the concentration of apple tissue which allowed to scavenge 50% of DPPH radical (EC50) totaled 2.34 mg d.m./mL. Similar findings regarding polyphenols were presented by Duda-Chodak et al. [10] for the same cultivar -Ligol, whereas around three times higher concentration was noted for Idared [34]. It means that amount of polyphenols is highly dependent on the apple variety. ...
... Analogous linear relationship was reported previously for apples (var. Idared) [34]. The sonication treatment significantly altered the phenolic content and thus antioxidant activity in the investigated apples. ...
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. Sustainability 2021, 13, x FOR PEER REVIEW 11 of 16 reported that antioxidant activity is correlated with reducing power. ...
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. ...
Citation: Hossain, M.S.; Ramachandraiah, K.; Hasan, R.; Chowdhury, R.I.; Kanan, K.A.; Ahmed, S.; Ali, M.A.; Islam, M.T.; Ahmed, M. Application of Oxalic Acid and 1-Methylcyclopropane (1-Mcp) with Low and High-Density Polyethylene on Post-Harvest Storage of Litchi Fruit. Sustainability 2021, 13, 3703. https://doi.org/10.3390/su 13073703 Academic Editor: Dario Donno
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. Sustainability 2021, 13, x FOR PEER REVIEW 11 of 16 reported that antioxidant activity is correlated with reducing power. ...
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. ...
Citation: Hossain, M.S.; Ramachandraiah, K.; Hasan, R.; Chowdhury, R.I.; Kanan, K.A.; Ahmed, S.; Ali, M.A.; Islam, M.T.; Ahmed, M. Application of Oxalic Acid and 1-Methylcyclopropane (1-Mcp) with Low and High-Density Polyethylene on Post-Harvest Storage of Litchi Fruit. Sustainability 2021, 13, 3703. https://doi.org/10.3390/su 13073703 Academic Editor: Dario Donno
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. Sustainability 2021, 13, x FOR PEER REVIEW 11 of 16 reported that antioxidant activity is correlated with reducing power. ...
... Several bioactive compounds (ascorbic acid, anthocyanins, phenol, and flavonoid content) could have contributed to this study's higher reducing power reduction. However, the loss of reducing power is related to the oxidation of polyphenolic compounds, complex formation with other food components, or transformation from active polyphenols to inactive compounds [46]. ...
The present study investigates the effects of oxalic acid and 1-methylcyclopropane (1-MCP) treatments in combination with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) on the post-harvest storage of litchi fruits. The physicochemical properties, bioactive compounds, antioxidant activities, and dismutase enzyme activity (SOD) of treated and untreated litchi fruits were examined during 30 days of storage at 4 ℃. The most effective combination was 1-MCP and HDPE packaging, which lowered the weight loss and preserved the red pericarp. Fruits treated with 1-MCP and HDPE also exhibited higher content of ascorbic acid (74.73–34.95 mg/100 g), total phenol (55.70–28.83 mg/100 g), and total flavonoid content (82.46–48.54 mg/100 g), whereas anthocyanin content (0.24–0.39 mg/100 g) was lowered during the entire storage period. In addition, higher levels of DPPH activity, reducing power, and SOD activity were observed in 1-MCP and HDPE-treated fruits. While antioxidants, SOD activities, and acidity were positively associated with total phenol and flavonoid content, these were negatively associated with anthocyanin content. Thus, the combined treatment of 1-MCP and HDPE are proposed as a sustainable strategy to preserve red pericarp, improve quality, and increase fruit shelf life of litchi.
... The sample of the material was homogenized with an aqueous solution of ethanol (80%) and boiled for 3 min. Afterwards, the extract was filtered [54]. Three extraction experiments were carried out and the mean value was taken for the data analysis. ...
... The antioxidant capacity was measured spectrophotometrically based on the degree of scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH; Sigma Aldrich, St. Louis, USA) radical by antioxidants present in fresh and dried soups extracts within the 30-min time period. The method was described by Brand-Williams et al. [55] and modified by Nowacka et al. [54]. The base solution of DPPH was prepared by solute of DDPH in a 99% solution of methanol. ...
The aim of this study was to investigate selected physical and biochemical properties of four vegetable freeze-dried soups. The water content, water activity, pH, color parameters, antioxidant activity (EC50), total polyphenolic content of fresh tomato, pumpkin, beetroot, and cucumber, and freeze-dried soups were measured. Sensory analysis was applied to compare sensory attributes of fresh and rehydrated soups. The sorption isotherms of freeze-dried soups were obtained with the application of the static and dynamic vapor sorption (DVS) method. The application of the freeze-drying method enabled the obtaining of dry soups with a low water content of 2–3%. The drying caused a significant change of color of all soups. The redness of soups decreased after drying for the beetroot soups from +39.64 to +21.91. The lower chroma value of 25.98 and the highest total color change ΔE*ab = 36.74 were noted for freeze-dried beetroot soup. The antioxidation activity and total polyphenolic content were reduced after drying, especially for the cucumber and tomato soups. The Peleg model was selected to describe the sorption isotherms of dried soups. The sorption isotherm of freeze-dried cucumber and beetroot soups had a sigmoidal shape of type II. The shape of the moisture sorption isotherm for freeze-dried tomato and pumpkin soups corresponded more with type III isotherms. The DVS method can be used to characterize the moisture sorption isotherms of freeze-dried products.
... Phenolic compounds were extracted from the plant material with 80% ethanol solution, as previously described by Nowacka et al. [2014]. The extracts were prepared in duplicate for each type of material and were used for total phenolic content and free radical scavenging activity determinations. ...
... The extracts were prepared in duplicate for each type of material and were used for total phenolic content and free radical scavenging activity determinations. Total phenolic content (TPC) was determined according to Folin-Ciocalteu (FC) methodology [Nowacka et al. 2014]. For this purpose, 30 cm 3 of distilled water, 1.5 cm 3 of extract, and 2.5 cm 3 of FC reagent were mixed in a flask. ...
... To 0.6 g ± 0.001 g of spray-dried powder 30 ml of distilled water was added, then vortexed till obtained homogeneous solution. Prepared material was infiltrated into volumetric flask and filled to 50 ml with distilled water (Nowacka et al. 2014). Two test-tubes for each sample were prepared. ...
... The extracts were prepared according to methodology presented by Nowacka et al. (2014) with some modifications. Water extracts were prepared for measurement: spray-dried powders (A), chokeberry juice concentrate (B) and solution of chokeberry juice (C). ...
Chokeberry juice is used in the food industry because of its antioxidant activity as well as anti-diabetes, anti-mutagenic, bacteriostatic, anti-inflammatory and anti-virus properties. However in a liquid form its active ingredients can be unstable, so conversion into powder form is required. To improve the quality of the final product and extend information about the properties of chokeberry powder the aim of the study was to examine the relationship of inlet air temperature (160 °C, 200 °C) and carrier type maltodextrin (MD) 10DE and 15.6DE, arabic gum (AG) and their mixtures (AG:MD10 and AG:MD15—1:1, 1:3, 3:1) with the amounts of anthocyanins and polyphenols and selected physical properties of powders obtained after spray drying. Moreover stability of anthocyanin was tested after storage Obtained powders were characterized by low water activity (< 0.26), high dry matter content (97–99%) and good hygroscopic properties. Saccharification level of maltodextrin had no impact on the amount of bioactive components enclosed inside the capsules. Moreover, the mixtures of carriers, AG:MD appeared to have a large potential to ensure a high quality of chokeberry powder with high content of anthocyanin (1694–2028 mg/100 g) and polyphenols (about 3000 mg/100 g d.m.). Storage temperature mostly has no statistically significant influence on content of active ingredients, but an increase in colour coefficents was observed. The contents of anthocyanins and polyphenols were higher in powders stored at 4 °C than at 25 °C.
... Phenolic compounds were extracted from the intact and PEF treated samples by 80% ethanol solution (Nowacka et al., 2014;Sledz et al., 2013). Extracts were prepared in two replications for each type of material and were used for the determination of the content of total phenolic compounds and antioxidant activities. ...
... The total phenolic content (TPC) was determined according to the Folin-Ciocalteu procedure proposed by Singleton et al. (1999) with some modifications (Nowacka et al., 2014;Sledz et al., 2013). For this purpose, 30 mL of distilled water, 1.5 mL of extract and 2.5 mL of Folin-Ciocalteu reagent (POCH, Gliwice, Poland) were mixed and after 3 min the 5 mL of 1.7 M sodium carbonate was added. ...
In this study, the impact of a pulsed electric field (PEF) treatment on the final quality of freeze-dried apples was investigated. The PEF treatment has been performed at an electric field intensity equal to 1.07 kV/cm and a specific energy input of 0.5, 1 and 5 kJ/kg. The samples were freeze-dried (without a separate pre-freezing step) at varying temperatures (set on 40 °C and 60 °C) and pressures (0.1, 0.25 and 1 mbar). The quality of dried material was evaluated by the analysis of residual moisture content, macro- and microscopic properties, colour, the total content of phenolic compounds and the antioxidant activity as well as texture and acoustic properties. It was found that the residual moisture content of PEF treated samples was reduced by up to ∼82% in comparison to the intact tissue. For electroporated samples, a good preservation of macro-shape, an inhibition of shrinkage and the development of large pores were observed. The PEF treated material exhibited a higher total phenolic content, but a smaller antioxidant activity. Mechanical and acoustic analysis showed a higher crunchiness and brittleness for PEF-treated tissue, whereas untreated tissue was characterised by a harder and rather crackly texture.
... Color is recognized as a major factor affecting raw materials and food product acceptance. It is known that natural pigments can participate in different reactions and hence, generally they can be considered as unstable during processing or storage (Nowacka & Witrowa-Rajchert, 2010;Puértolas et al., 2013;Wilska-Jeszka, 2007). Therefore, a lot of effort is put to find optimal processing conditions or new processing methods which could enhance or preserve the native optical properties of treated material. ...
... PEF treatment as a non-thermal technique may have no significant detrimental effect on heat-labile components present in food such as vitamins or antioxidants (Vega-Mercado et al., 2007). It is known that properties of bioactive food components can change significantly during the thermal food processing (Nowacka & Witrowa-Rajchert, 2010). Fruits and vegetables are reported to contain a wide variety of antioxidant components, including carotenoids, vitamins, phenols, flavonoids. ...
... A combinational use of convective and IR dryers can offer the advantages of both methods (i.e., maintaining the quality of the final product and shorter drying time) [22]. Hybrid dryers have been used for drying various products including rice by fluidized bed-IR-microwave [23], apple by microwave/CV and CV/IR [24], chrysanthemum by CV/IR dryer [25], walnut kernel by the IR-vacuum and IRfluidized bed with microwave pretreatment [26], tomato by CV/IR and microwave-CV [27], and okra by IR-freeze-drying and microwave vacuum [28]. ...
In this research, a convective/infrared (CV/IR) dryer was used to dry pumpkin slices. For optimization of the drying conditions, the influence of three levels of independent variables including air temperature (40, 55, and 70 °C), air velocity (0.5, 1, and 1.5 m/s), and IR power (250, 500, and 750 W) were assessed by response surface method (RSM) through a face-centered central composite design. Analysis of variance (non-fitting factor and R2 value) was employed to determine the desirability of the model. Response surfaces and diagrams were also utilized to show the interactive influence of the independent variables with the response variables (drying time, energy consumption, shrinkage, total color variation, rehydration ratio, total phenol, antioxidant, and vitamin C contents). According to the results, optimal drying conditions involved a temperature of 70 °C, air velocity of 0.69 m/s, and IR power of 750 W. At the mentioned conditions, response variables of drying time, energy consumption, shrinkage, color, rehydration ratio, total phenol, antioxidant, and vitamin C contents were 72.53 min, 24.52 MJ/kg, 23%, 14.74, 4.97, 617.97 mg GA/100 g dw, 81.57%, and 4.02 mg/g dw, with a confidence level of 0.948, respectively.
... The total polyphenolic content was determined using Folin-Ciocalteu method, in accordance with modified procedure presented previously by Nowacka et al. [2014] and Wiktor et al. [2016]. Extraction from the samples was carried out using an 80% ethanol solution. ...
The objective of the research study was to determine of on biochemical proper-ties and bioactive compounds content changes of kiwiberry (Actinidia arguta) stored for up to 10 days at storage temperature (5, 15, 25°C) then kiwiberry fruits was frozen and stored until testing. This work examines the temperature and storage time of the fruit of the Actinidia arguta on their acidity, flavonoid content, the total content of polyphenol compounds and antioxidant activity. The results resulted in the finding that different tem-peratures and storage time had a statistically significant effect of the physico-chemical properties of the minikiwi fruit. The use of higher temperatures accelerated the ripening process, which resulted in a decrease in fruit acidity. Additionally, during storage at higher temperatures an increase in the content of valuable compounds, including flavonoids having a beneficial effect on human health, was noted.
... The extracts were prepared according to methodology presented by Bednarska & Janiszewska-Turak (2020) and Nowacka et al. (2014). Water extracts of spraydried powders were prepared for measurement: for this purpose, 0.3 g of material (AE0.0001 ...
The aim of this study was to evaluate the influence of bacteria type and carrier addition during microencapsulation process by spray‐drying on the microorganism survival and physicochemical properties of fermented beetroot juice powder. Selected bacteria were as follows: L. fermentum, L. plantarum and L. brevis and its mixture in proportion 1:1:1. Fermented beetroot juice containing selected LAB was spray‐dried at 160 °C. Maltodextrin and gum Arabic were used as drying carriers at 10% (w/w). All powders were stable (low water activity below <0.25, high dry matter content 95–98%). Bacteria type had the main influence on the chemical properties and amount of bacteria. The highest bacteria content was observed in powders with L. brevis as a starter, and the same was observed for polyphenols and betalain content. However, the method of drying fermented juices still needs to be refined due to the 50% reduction in the number of microorganisms during the drying process.
... All cultivars showed a significant decrease in TAC with each measurement throughout the cold storage period ( Table 2) which is due to the decomposition of antioxidants throughout the storage period [41]. Total phenolic compounds content were expressed as gallic acid equivalents (GAE) in a Kg of fresh fruit tissue Total antioxidant capacity was expressed as the percentage of neutralized DPPH radicals ...
Pre-harvest nutritional condition is one of the major fruit quality influencers in apple whether directly after harvest or throughout cold storage. Here, the influences of various levels of ammonium to nitrate on vitamin C content, total phenolic compounds, and total antioxidant capacity of three apple cultivars ('Granny Smith', 'Gala', and 'Golab Kohans') throughout cold storage period were studied. Five different ammonium nitrogen levels (0, 0.08, 0.16, 0.19, and 0.27 meq/L) were applied. After harvest, the fruits were transferred to cold storage and stored at 0±1˚C for 45, 90, and 160 days for 'Golab Kohans', 'Gala', and 'Granny Smith', respectively. Vitamin C content, total phenolic compounds, and total antioxidant capacity were determined throughout the storage period. The results showed that all cultivars showed different responses toward ammonium nitrogen application in terms of vitamin C content. 'Golab Kohans' recorded an increase in vitamin C content by increasing ammonium in nutrition solutions. On the other hand, minor changes were recorded in 'Granny Smith' and 'Gala'. Total phenolic compounds and total antioxidant capacity were significantly increased under all tested levels of ammonium in comparison to control in all cultivars. Furthermore, all cultivars showed a significant decrease in vitamin C, total phenolic compounds, and total antioxidant capacity throughout cold storage, indicating that these bioactive compounds were subjected to decomposition and metabolic degradation during the storage period. Surface response analysis results showed that more vitamin C degradation was attributed to the increase in ammonium application, while less total phenolic compounds degradation and total antioxidant capacity decrease were observed under similar treatments.
... It also depended on other factors, including the properties of processed material, water content, oxygen availability, etc. (Fang and Bhandari 2011). The impact of the high temperature on the content of polyphenols was examined by Fang and Bhandari (2011) and Nowacka and Witrowa-Rajchert (2010), who observed their degradation during the drying process. ...
The objective of this study was to explain the effect of osmotic dehydration pre-treatment (chokeberry juice or inulin) and drying method (microwave-convective drying or freeze-drying) on polyphenols content, antioxidant activity and sensory properties of dried strawberries. The addition of a chokeberry juice concentrate to the osmotic solution significantly influenced the increase of polyphenols content in the fruit. Their content was significantly higher in the samples treated via osmotic dehydration in solutions containing the chokeberry juice concentrate, followed by freeze-drying and also by microwave-convective method. The ability to bind DPPH• radicals ranged from 40% in the dried strawberries without osmotic dehydration to 82% in fruit osmo-dehydrated in a mixture of inulin and the chokeberry juice concentrate and dried by freeze-drying. Study results indicate that the concentrated chokeberry juice and inulin can be used as beneficial osmotic substances. The dried strawberries can represent an alternative to snacks or may be attractive component of other products. One of the very attractive proposals for today’s increasingly demanding consumers can therefore be dried fruit snacks enriched with natural bioactive ingredients.
... Ultrasound pre-treatment led to a significant increase of weight reduction and water loss in all the samples. It is well known that ultrasound create microscopic channels which may ease moisture removal and increase the diffusivity of the water (Fernandes, Gallão, et al., 2008;Fernandes & Rodrigues, 2007;Nowacka, Sled z, et al., 2014). On the other side, for SA_US and T_US samples the US pre-treatment did not promote any differences for solid gain, while it caused a significant decrease in samples STV_US. ...
Cranberries are appreciated for their high amount of antioxidants such as flavonoids, anthocyanins, phenolic acids, carotenoids and vitamins. However, due to their sour and tart taste they request to be processed into sweeter dried fruits in order to be acceptable for the consumers. The aim of this work was to analyse the effect of ultrasound assisted osmotic dehydration on mass transfer parameters and on quality characteristics during storage of cranberries. Ultrasound treatment was performed at the frequency of 21 kHz for 30 min in three osmotic solutions - 61.5% sucrose, 30% sucrose with an addition of 0.1% of steviol glycosides and 40% trehalose on cut in half cranberries. Afterwards, the cranberry samples were subjected to osmotic dehydration process at 40 °C for 72 h. The osmodehydrated samples both with or without ultrasound pre-treatment were collected and stored at 10 °C in climatic chamber in microperforated plastic bags (PLA) for 8 weeks. The weight reduction, dry matter, water activity, colour, and microbiological analysis were performed after 1, 2, 4 and 8 weeks of storage. The obtained results indicated that ultrasound application significantly affected the mass transfer parameters during osmotic treatment, as well as it did the type of osmotic solution used. Thermal analysis showed variations in sugar melting temperature and enthalpy as a result of osmotic treatment and storage. During the storage, lower weight loss and higher lightness were observed in US pre-treated samples. The sample that preserved the best chemico-physical and microbiological characteristics during storage was the one treated with 61.5% sucrose solution, due to its lowest water activity.
... For this purpose, 3 g of sample (±0.0001 g accuracy) was placed in the beaker and 25 mL of an 80% (v/v) aqueous ethanol solution was added. The samples were homogenized, boiled and then the extract was filtered into a 50 mL volumetric flask, which was filled with ethanol solution [33]. The procedure was repeated thrice for each type of the material. ...
The aim of the study was to investigate the effect of ultrasound treatment in two osmotic solutions, carried out at different time, on some physical properties, antioxidant activity and cell survival of cranberries. Ultrasound treatment was conducted at 21 kHz for 30 and 60 min in liquid medium: 61.5% sucrose solution and 30% sucrose solution with 0.1% steviol glycosides addition. Some samples before the ultrasound treatment were subjected to cutting or blanching. The results showed that dry matter content and concentration of the dissolved substances increased during ultrasound treatment in osmotic solution, however higher value was observed for treatment in 61.5% sucrose solution and for longer time. Water activity and volume of cranberries did not change after the ultrasonic treatment. Combined treatment led to colour and antioxidant activity alterations as well. A cell viability of whole and cut samples decreased after 60 min of osmotic treatment and completely lost in the blanched samples.
... The samples were homogenized and boiled. The extract was filtered into a volumetric flask and filled to 50 mL with ethanol solution [16]. The procedure was repeated thrice for each type of material. ...
The aim of the study was to investigate the influence of ultrasound treatment applied in osmotic solution on bioactive compounds, such as vitamin C, polyphenols, anthocyanins and flavonoids content as well as antioxidant activity in cranberries var. Vaccinium oxycoccus. Ultrasound treatment was performed at the frequency of 21 kHz for 30 and 60 min in two osmotic solutions - 61.5% sucrose and 30% sucrose with an addition of 0.1% of steviol glycosides. Before the ultrasound treatment the material was subjected to cutting and/or blanching. The obtained results indicated that the influence of ultrasound waves on cranberries depends on a type of bioactive component. The ultrasound treated cranberries as well as the ones subjected to cutting and/or blanching enhanced by ultrasound were characterized mainly by a lower content of bioactive compounds.
... An increase in relative humidity has a negative impact on the ascorbic acid content as well (Sigge et al. 1999). Furthermore, the reduction of polyphenols in apples during drying depends on drying time and follows a first order reaction (Nowacka et al. 2014). ...
Besides energy efficiency, product quality is gaining importance in the design of drying processes for sensitive biological foodstuffs. The influence of drying parameters on the drying kinetics of apples has been extensively investigated; the information about effects on product quality available in literature however, is often contradictory. Furthermore quality changes obtained applying different drying parameters are usually hard to compare. As most quality changes can be expressed as zero, first or second order reactions and mainly depend on drying air temperature and drying time, it would be desirable to cross-check the results in function thereof. This paper introduces a method of quality determination using a new reference value, the cumulated thermal load. It is defined as the time integral of the product surface temperature and improves the comparability of quality changes obtained by different experimental settings in drying of apples and tomatoes. It could be shown that quality parameters like color changes and shrinkage during apple drying and the content of temperature sensitive acids in tomatoes vary linearly with the integral of product temperature over time.
... Using near infrared spectroscopy to determine the in-situ decomposability of leaf material the authors found that polyphenols were negatively correlated with leaf persistence. Despite their usefulness in functional ecological research, an obstacle is seen in the sensitivity of extractable tannins and non-tannin phenolics in plant tissues to differences in sampling, sample storage and sample processing conditions (see [22] [23] [24] [25]). Mueller-Harvey [26] noted that leaves are best stored on ice or cooled directly after collection; conditions that in some biomes, such as tropical or subtropical regions, can hardly be met when collecting samples in the field. ...
Plant polyphenols are involved in important ecosystem processes and may affect nutrient cycling. Previous investigations have demonstrated detrimental effects of suboptimal sample treatment on the quantity of extractable plant polyphenols. We compared leaf polyphenol concentrations of 20 tree species from East China in two sample sets collected under different conditions: (a) according to established protocols and stored more than three years, (b) under conditions optimised for leaf polyphenols. We investigated the variance brought about by suboptimal sample handling as compared to the variance caused by the taxonomic range of species. Family-affiliation explained the largest proportion of variance, whereas sample handling had only minor effects. Reducing the taxonomic range increased the impact of differences in sample handling. Additionally, we showed that the concentrations of leaf polyphenols were phylogenetically more conserved than other leaf traits. Non-metric-multi-dimensional scaling revealed similar ordination patterns for leaf polyphenol concentrations in both sample sets with both ordinations being closely correlated. Finally, we computed separate ordinations including an extended set of leaf traits and found that both analyses led to similar ecological conclusions. Consequently, in studies comprising a wide taxonomic range, the adverse effects of suboptimal sample handling may be overridden by the variation brought about by phylogeny.
... Despite their usefulness in functional ecological research, an obstacle is seen in the sensitivity of extractable tannins and non-tannin phenolics in plant tissues to differences in sampling, sample storage and sample processing conditions (see [22][23][24][25]). Mueller-Harvey [26] noted that leaves are best stored on ice or cooled directly after collection; conditions that in some biomes, such as tropical or subtropical regions, can hardly be met when collecting samples in the field. ...
Plant polyphenols are involved in important ecosystem processes and may affect nutrient cycling. Previous investigations have demonstrated detrimental effects of suboptimal sample treatment on the quantity of extractable plant polyphenols. We compared leaf polyphenol concentrations of 20 tree species from East China in two sample sets collected under different conditions: (a) according to established protocols and stored more than three years, (b) under conditions optimised for leaf polyphenols. We investigated the variance brought about by suboptimal sample handling as compared to the variance caused by the taxonomic range of species. Family-affiliation explained the largest proportion of variance, whereas sample handling had only minor effects. Reducing the taxonomic range increased the impact of differences in sample handling. Additionally, we showed that the concentrations of leaf polyphenols were phylogenetically more conserved than other leaf traits. Non-metric-multi-dimensional scaling revealed similar ordination patterns for leaf polyphenol concentrations in both sample sets with both ordinations being closely correlated. Finally, we computed separate ordinations including an extended set of leaf traits and found that both analyses led to similar ecological conclusions. Consequently, in studies comprising a wide taxonomic range, the adverse effects of suboptimal sample handling may be overridden by the variation brought about by phylogeny.
The study aimed to optimize the ultrasound assisted osmotic dehydration process of white mulberry using response surface methodology. Effects of three variables including ultrasonic treatment time (10, 20, and 30 min), osmotic solution concentration (25, 42.5, and 60 % w/w), and frequency intensity (10‐90 %) were investigated. Three responses were studied; water loss (WL), sugar gain (SG), and color parameters (a*, b*, L*, and ΔE). Results represented that, in comparison to the osmotic dehydration alone, the application of ultrasonic treatment reduced the total processing time and increased effective water diffusivity. Results revealed that frequency intensity had significant effects on all response variables except for L* and b *. Increasing the frequency intensity led to increased WL (10 times) and ΔE in the samples and a decrease in SG (2.8 times). It was also observed that time‐ concentration interaction term of response models is statistically significant for all responses except for ΔE, a*and b*, while time‐amplitude interaction term was statistically significant for ΔE, alone. Finally, multi objective optimization according to the response surface models showed that the best conditions are osmotic solution concentration: 60%, frequency intensity: 75% and ultrasound time: 10 min. At this optimum conditions, WL, WR, SG, a*, b*, L* and ΔE were found to be 0.127%, 0.097%, 0.03 %, ‐3.700, 32.071, 81.969 and 3.955 respectively.
Drying is one of the most important steps in processing of edible insects biomass for their potential utilisation in food applications. In this study, the impact of pulsed electric field (PEF) pre-treatment (at E = 1.07 kV/cm and Wspec = 5 and 20 kJ/kg) on infrared-assisted air drying kinetics of black soldier fly (Hermetia illucens) and yellow mealworm (Tenebrio molitor) larvae has been evaluated. Moreover, microbial load and physical quality parameters of dried matter have been analyzed. The results show that PEF enhances the kinetics of water evaporation from insects biomass, especially in the range of the moisture ratio (MR) from 1.0 to 0.2. For instance, in the case of having been drying H. illucens larvae for 20 min, MR equalled 0.86, 0.75, and 0.72 for the untreated sample, 5 kJ/kg PEF-treated and 20 kJ/kg PEF-treated one, respectively. The effect of the PEF treatment was less visible in the case of H. illucens larvae and for low MR values. The PEF pre-treatment did not affect the water binding properties of dried insect biomass, regardless of species. However, the PEF pre-treated matter exhibited the same or even higher hygroscopic properties than the untreated ones. The difference in optical properties between untreated and PEF-treated samples was marginal. Nevertheless, for microbial contamination, 20 kJ/kg PEF treatment reduced the total number of microorganisms by 0.5–1.0 log cycle in comparison to the dried matter that had not been pre-treated. Nevertheless, the total number of microorganisms was too high to be feasible for food production purposes which would require additional operations to ensure food safety.
Industrial relevance
The interest in utilisation of insects as an alternative source of macronutrients for food and feed is growing tremendously. Drying is one of the most popular first steps in further processing technology applicable to insect biomass. Since air drying is one of the longest and the most energy consuming unit operation, there is a need to seek alternative methods that can be coupled with pre-treatment to enhance the process kinetics. In this paper, the combination of infrared drying of two species of insects preceded by pulsed electric field treatment has been discussed.
Different aspects of terebinth drying in a microwave-rotary dryer were investigated including energy and exergy analysis, quality, and bioactive compounds. Experiments were performed using different parameters of microwave power (270, 450, and 630 W) and chamber rotation speed (5, 10, and 15 rpm). Drying time and effective moisture diffusivity were ranging from 43 to 137 min and 6.25 × 10⁻⁹ to 9.28 × 10⁻⁸ m² s⁻¹, respectively. Energy and energy efficiency increase with increasing microwave power and rotation speed. Exergy loss and improvement potential decreased with increasing microwave power and rotation speed. The physical parameters (shrinkage and total colour difference) increased with increasing microwave and rotation speed, while for the rehydration rate, an inverse relationship was observed. Also for bioactive compounds like total phenolics, total flavonoid content, and antiradical activity, a higher reduction was noticed with used higher microwave power and with higher rotation speed. Thus, the best parameters to obtain the highest content of bioactive compounds were microwave power of 270 W and rotation speed of 5 rpm. Comparison of different algorithms revealed that the grey wolf optimisation (GWO) algorithm had greater accuracy than the whale (WO) optimisation algorithm to predict all parameters of dried terebinth.
Most agricultural products are harvested with a moisture content that is not suitable for storage. Therefore, the products are subjected to a drying process to prevent spoilage. This study evaluates an infrared rotary dryer (IRRD) with three levels of infrared power (250, 500, and 750 W) and three levels of rotation speed (5, 10, and 15 rpm) to dry terebinth. Response surface methodology (RSM) was used to illustrate and optimize the interaction between the independent variables (infrared power and rotation speed) and the response variables (drying time, moisture diffusivity, shrinkage, color change, rehydration rate, total phenolic content, and antioxidant activity). As infrared power and rotation speed increased, drying time, rehydration rate, antioxidant activity, and total phenolic content decreased, while the other parameters were increased. According to the results, the optimum drying conditions of terebinth were determined in the IRRD at an infrared power of 250 W and drum rotation speed of 5 rpm. The optimum values of the response variables were 49.5 min for drying time, 8.27 × 10−9 m2/s for effective moisture diffusivity, 2.26 for lightness, 21.60 for total color changes, 34.75% for shrinkage, 2.4 for rehydration rate, 124.76 mg GAE/g d.m. for total phenolic content and 81% for antioxidant activity.
The aim of the study was to analyse the effect of osmotic treatment assisted by ultrasound on the physico-chemical properties of blueberries from Suceava county, Romania. Ultrasound treatment was conducted at the frequency of 25 kHz (using different values of amplitude – 20, 60 and 100%, respectively) in 61.5% sucrose solution at 30, 40 and 50 °C for 20, 40 and 60 min. The Box-Behnken design was used to investigate the influence of independent variables (time, temperature and amplitude) on the osmotic dehydration. The results showed that for physico-chemical characteristics (mass transfer parameters; moisture content; total content of anthocyanins, flavonoids and polyphenols; DPPH assay scavenging activity) that optimal conditions were obtained at 30 °C for 40 min at a 100% amplitude. Ultrasound treatment stimulated changes in the main characteristics, especially of colour leading to a higher lightness (L*), decreasing AsA-POD and water activity. The results indicated that the higher the values of independent variables are, the more representative is the correlation between them.
Background and Objective: Apples play an essential role in human nutrition, as they are a well-documented source of natural antioxidants as vitamins, carotenoids and phenolic compounds. This research was conducted to study some bioactive compounds and activities of five apple varieties (Black, Apricot, Jester, Big Ariane and Medium Ariane). Materials and Methods: In vitro antioxidant and anti-inflammatory activities were determined and analyzed by using a spectrophotometer. Replications of all apple varieties were applied to ANOVA test using SPSS (20.00). Significant differences between means (±SD) were significant at (p<0.05) by using Duncanʼs New Multiple Range Test. Results: Medium Ariane apples had the highest total antioxidant value followed by Big Ariane, Apricot, Black and Jester apples. Apricot had the highest antioxidant activities, (93.67, 7.71 and 85.98 µmol TE g-1 fw) for DPPH, ABTS and FRAP, respectively. Total phenol values were 21.65-35.11 mM and the total flavonoids were 36.86-55.52 mg Qe g-1. The extracts showed high anti-inflammatory activity values (0.32-5.46 µg mL-1). Medium Ariane, Jester and Apricot had highly anti-inflammatory activity followed by Big Ariane and Black extracts, respectively. Conclusion: The results presented that apples, especially Apricot variety had the highest bioactive compounds, antioxidant and anti-inflammatory activities.
The aim of this study was to investigate the effects of pre-treatment in ethanol solution carried out in variable time with and without ultrasound (US) assistance on convective drying kinetics, total phenolic content (TPC) and hygroscopicity of an apple. The drying time after immersion in ethanol solution was shorter up to 13.4 (without US) and 18.3 % (with US) in comparison to intact slices. The most appropriate model that described kinetics of drying was the one proposed by Sledz et al. Drying of the untreated apple resulted in a decrease of the TPC by 18 %, compared with raw apples and the pre-treatment led to further losses. The tissue after ethanol pre-treatment was less hygroscopic, which proves the possibility to maintain a characteristic texture of the dried apple with prolonged storage stability. The best quality of dried apples was obtained after 1 min of ethanolic pre-treatment with US.
Parsley leaves contain a high amount of bioactive components (especially lutein), therefore it is crucial to select the most appropriate pre-treatment and drying conditions, in order to obtain high quality of dried leaves, which was the aim of this study. The optimization was done using response surface methodology (RSM) for the following factors: microwave power (100, 200, 300 W), air temperature (20, 30, 40 °C) and pre-treatment variant (ultrasound, steaming and dipping as a control). Total phenolic content (TPC), antioxidant activity, chlorophyll and lutein contents (using UPLC-PDA) were determined in dried leaves. The analysed responses were dependent on the applied drying parameters and the pre-treatment type. The possibility of ultrasound and steam treatment application was proven and the optimal processing conditions were selected.
The ethanol extracts of apple fruits harvested from the cultivars Aldas, Auksis, Ligol, and Lodel grown in Lithuania were analyzed by the high-performance liquid chromatography method. Chlorogenic acid was found to be a predominant component in the apple fruits of all the cultivars, except the cultivar Ligol. (-)-Epicatechin was the major compound in the ethanol extracts of apple fruits obtained from all the cultivars, while the amount of (+)-catechin was lower. The following quercetin glycosides were identified and quantified: hyperoside, isoquercitrin, avicularin, rutin, and quercitrin. Hyperoside was the major quercetin glycoside in apple fruits.
The in vitro total antioxidant capacity (TAC), and the total phenol (TP) contents of commercial fruit juice samples widely consumed in Turkey were determined. TAC methods were more recently developed methods (TAC1 and TAC2) using Fe-o-dianisidine complex and ABTS radical, FRAP (Ferric Reducing Ability of Plasma) method (TAC3). Folin Ciocalteu assay were used for determining TP contents and the mean TP results were well correlated significantly and positively with the TAC2 and TAC3 results. Among the fruit juice, orange had the highest TAC1, strawberry had the highest phenol, TAC2, and TAC3 values. Generally, strawberry and sour cherry samples had the highest TP, TAC2, and TAC3 values.
The effects of pretreatment solutions and drier types (solar vs sun) were investigated for grapes (var. sultanas). Pretreatment solutions containing 5% K2CO3 plus 1.5% olive oil and 4% K2CO3 plus 2% ethyl oleate accelerated drying rates nearly to the same extent, as compared to untreated grapes. Drying rates were classified for the tested drying methods: solar drying > sun drying on concrete ground > sun drying on wooden racks, or on polypropylene canvas sheets. Increasing K2CO3 concentration from 4 to 7% in ethyl oleate (2%) solution increased drying rates on concrete ground. Treatment with SO2 gas (645 mg/kg) in addition to ethyl oleate, further increased the drying rates but the color of the product was rated to be too light and unacceptable to the market. The moisture content and color intensities of the sun-dried grapes were found to be non-uniform. Storage stability of treated, dried grapes was investigated in (1) modified atmosphere (1% O2 plus 13% CO2), (2) vacuum packed and (3) ordinary plastic pouch packed storage at 6 °C. Untreated grapes had the lowest Hunter L (lightness), a (redness) and b (yellowness) values compared to treated grapes. Storage caused color parameters to decline, but this reduction was less pronounced for SO2 gas treated products.
Total polyphenolics and free radical scavenging properties of extracts obtained from osmotically dehydrated, and spiced mushroom snack food with raw unprocessed mushrooms were studied. Sensorially acceptable mushroom snack was prepared in the laboratory by osmotically dehydrating Agaricus bisporous in 5% salt solution followed by addition of an adequate combination of spices and vacuum drying. The extracts of raw and dry snack-mushrooms were then evaluated for their scavenging activities against the 2,2-diphenyl-1-picryhydrazyl (DPPH) free radical and 2,2-azobis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS). The scavenging activity of free extracts of raw and dry snack mushrooms on DPPH radical were 76% and 72%, respectively. The ABTS radical scavenging activity of the free extracts of raw sample expressed as ascorbic acid equivalent antioxidant activity (AEAC) was 2.76 mg ascorbic acid equivalents/100 g and 2.67 mg ascorbic acid equivalents/100 g snack mushroom. Both free and bound polyphenolic contents in mushroom snacks were slightly higher than raw mushrooms whereas total flavonoids levels decreased marginally. No change in antioxidants status of the dry snack product was observed when dry snack stored at ambient temperature for up to 15 days. The results of this study suggested that mushroom snacks prepared using a combination of the above methods was able to retain a significant amount of antioxidants, phenols and flavonoids and mushroom snacks may prove to be an alternative nutritious snack.
This study examined the effects of freezing, storage, and cabinet drying on the anthocyanin content and antioxidant activity of blueberries (Vaccinium corymbosum L). Fresh samples were stored for two weeks at \5^\circ C while frozen samples were kept for up to three months at C. There were two drying treatments, one including osmotic pretreatment followed by cabinet drying and the other involving only cabinet drying. Total anthocyanins found in fresh blueberries were mg/g dry matter, expressed as cyanidin 3-rutinoside equivalents. In comparison with fresh samples, total anthocyanins in untreated and pretreated dried blueberries were significantly reduced to mg/g solid content, 41% loss, and mg/g solid content, 49% loss, respectively. Osmotic treatment followed by a thermal treatment had a greater effect on anthocyanin loss than the thermal treatment alone. In contrast, the frozen samples did not show any significant decrease in anthocyanin level during three months of storage. Measurement of the antioxidant activity of anthocyanin extracts from blueberries showed there was no significant difference between fresh, dried, and frozen blueberries.
Methods available for the measurement of antioxidant capacity are reviewed, presenting the general chemistry underlying the assays, the types of molecules detected, and the most important advantages and shortcomings of each method. This overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. From evaluation of data presented at the First International Congress on Antioxidant Methods in 2004 and in the literature, as well as consideration of potential end uses of antioxidants, it is proposed that procedures and applications for three assays be considered for standardization: the oxygen radical absorbance capacity (ORAC) assay, the Folin-Ciocalteu method, and possibly the Trolox equivalent antioxidant capacity (TEAC) assay. ORAC represent a hydrogen atom transfer (HAT) reaction mechanism, which is most relevant to human biology. The Folin-Ciocalteu method is an electron transfer (ET) based assay and gives reducing capacity, which has normally been expressed as phenolic contents. The TEAC assay represents a second ET-based method. Other assays may need to be considered in the future as more is learned about some of the other radical sources and their importance to human biology.
Foods that we eat supply our bodies with nutrients essential for good health. Foods that are classified as functional foods contain components that impart health benefits beyond basic nutrition. An example of a functional food is fruits, which are good sources of antioxidants. In addition to the usual nutrients such as vitamins and minerals, fruits are also rich in anthocyanins, flavonoids, and phenolic acids. Today’s consumers are more educated and increasingly demand functional foods. Though the mechanisms through which they work are not always clear, when eaten on a regular basis as part of a varied diet, functional foods may lower the risk of developing certain diseases. It is estimated that more than 5000 phytochemicals have been identified. However, a large percentage remains unknown and needs to be identified before their health benefits are fully understood.
A solar drying process for persimmon (Diospyros kaki) was developed. The ripened but hard fruits were sliced (2.5-3.0 mm) and sulphited (0.2% SO2, 3 min) before drying in a solar cabinet dryer. It took about 10 hours for the samples to reach a moisture content of 15-16%. The moisture content of the dried fruit ranged from 14.3 to 16.8% after storing for 6 months at ambient temperature (18 degrees-30 degrees C). The ascorbic acid content of the dried fruit ranged from 116.0 - 126.0 mg/100 g. A significant (P<0.05) reduction in this vitamin was recorded after 6 months of storage with values ranging from 102 to 109 mg/100 g. Phenolic compounds such as sinapine, catechin, anthocyanidin, leucoanthocyanidin and total phenols which impart astringency showed a decreasing trend during storage. Although all the dried samples were completely non-astringent, on sensory evaluation, the sulphited samples were rated higher (7.8) than control samples (6.1) for overall acceptability scores.
The hypothesis that the rehydration process reflects the changes incurred to the plant material by drying has been proved. Creation of space with larger surface area made by mechanical destruction of internal structures is the evidence of physical changes occurring in plant materials during drying. Different course of water imbibition, way of mass and volume increase, change of the state of equilibrium between crystalline and amorphous regions are the confirmation of physicochemical changes. Leaching of solubles and the loss of plant tissue respiration ability confirm biological changes in dried materials.
The purpose of this study was to determine the influence of the internal structure of dried apples on such physical properties as density, porosity, or shrinkage. Apple slices were dried using convection, microwave-convection, and infrared-convection methods. The apple slices dried by means of the microwave and infrared methods showed between 11 to 12% lower shrinkage, 30-34% lower volume, 18-23% lower density, and porosity of 25-28% higher than the slices dried exclusively by the convection method. Considerable differences in the density and porosity of the apple slices dried using the above methods were confirmed by analyzing the tissue images made with the help of scanning electron microscopy. Convective drying caused significant changes in the actual size and distribution of the apple cells. The cells dried using both the microwave and infrared methods had a larger cross-sectional area compared with the convective-dried material. 2009 Taylor & Francis Group, LLC.
Little detailed information is available for the far-infrared and microwave drying characteristics on peach and far-infrared combined with microwave drying on other food products. Experiments were conducted to study microwave and far-infrared dehydration characteristics and two-stage drying process involving far-infrared following microwave drying on peach. As microwave drying power and infrared drying power increased, dehydration rate of peach increased and whole drying energy consumption decreased. Peach experienced two falling rate periods when dried with microwave drying or far-infrared drying, and the first falling rate period under moisture content of peach more than 1.7 (dry basic, d. b.), the second falling rate period under less than moisture content 1.7 (d. b.). The same water loss will consume more energy and the steeper curve of energy versus moisture content were obtained when the moisture content is less than 1.7 (d. b.). However, differed from microwave drying, an accelerating dehydration rate period existed in the initial period of far-infrared drying. The effects of infrared drying power, microwave drying power and exchanging moisture content at former far-infrared drying converting into latter microwave drying (three factors) on energy consumption rate and sensory quality (two indices) are significant. The interaction effect of infrared drying power and exchanging moisture content on two indices is significant. The effects of second-order of microwave drying power and of interaction between infrared drying power and microwave drying power on energy consumption rate were not significant. The effects of second-order of exchanging moisture content and of interaction between exchanging moisture content and microwave drying power on sensory quality were not significant.
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.
Banana samples (4.3±0.177,7.4±0.251and14±0.492 mm thick) were dried using the following drying regimes; convection (60°C at 1.45 m/s); microwave (350, 490 and 700 W power) and convection followed by microwave (at 350 W, 4.3 mm thick sample) finish drying. The drying of banana slices took place in the falling rate drying period with convection drying taking the longest time. Higher drying rates were observed with the higher power level. Microwave finish drying reduced the convection drying time by about 64.3%. A physical model was employed to fit the experimental data and gave good fit for all experimental runs except microwave finish data. Microwave finish dried banana was lighter in colour and had the highest rehydration value.
This work aimed at studying the effects of pretreatment, namely, hot water blanching, and hot air-drying (60–120°C) on the evolutions of vitamin C, phenolic compounds, nomilin and limonin, which are potential bioactive compounds in lime residues during drying. Blanching was found to decrease both the antioxidant contents and activities of the residues due to thermal degradation and loss with the blanched water. During drying, nomilin and limonin contents first increased, probably due to the remaining enzyme activity after blanching. After this period, the amounts of both nomilin and limonin dropped rapidly, due to thermal degradation. Product temperature was found to be a major factor controlling the changes of limonoids and there was no direct correlation between the moisture change during drying and limonoid contents. During degradation of vitamin C and phenolic compounds, the amounts of both substances decreased as the product temperature increased and the moisture content decreased during drying. The amount of phenolic compounds correlated well with the total antioxidant activity and phenolic compounds were found to be a major contributor to antioxidant activity of the product.
The development of new citrus products, such as dry products for direct use or for rehydration, is interesting to promote their consumption. Combined microwaves (MW)–air (2 m/s, 60 °C) drying of orange slices has been studied in terms of process kinetics and of the rehydration capability as affected by the applied MW power (0, 0.17, 0.36, 0.69 and 0.88 W/g). Drying curves were modelled considering two periods, with different kinetic constants, related with the effective water diffusivity. These constants increased linearly with the applied MW power and, despite the low levels of MW power used, a sharp reduction in drying time of orange slices was obtained. Rehydration behaviour of orange slices was modelled through Peleg's and Weibull's equations. No differences in rehydrating behaviour were observed as a function of the applied MW power. So, the highest level, which was limited to avoid sample browning, will be recommended to reduce the drying time.
Dried shrimp is a high value fishery product of Thailand. Since it is known that drying and storage conditions affect the color changes of dried shrimp, but the quantitative information on this aspect is still very limited, the objective of the present study was to investigate the long-term effects of drying air temperature (80, 100, 120 °C) and various storage parameters, namely, storage atmosphere (air, vacuum) and storage temperature (4, 15, 25 °C), on the kinetics of astaxanthin degradation and of color changes, in terms of CIELAB parameters L∗, a∗ and b∗, of dried shrimp during 16-week storage. In addition, the relationship between astaxanthin retention ratio and color retention ratio of dried shrimp was established. The degradation of astaxanthin and color loss was found to follow a first-order kinetic reaction; the temperature dependence of reaction constants was found to be well explained by the Arrhenius relationship. Drying shrimp at higher temperature led to lower astaxanthin degradation during storage than drying at lower temperatures. Storage of dried shrimp under vacuum atmosphere at low temperatures enhanced the retention of astaxanthin in dried shrimp. Good correlations between astaxanthin degradation and color changes were also observed.
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.
Clear and cloudy apple juices from Idared and Champion varieties were studied for their radical-scavenging effects. The polyphenolic content and composition of the juices before and after thiolysis were determined by high-performance liquid chromatography with diode array detection. Cloudy juices, especially that prepared from Champion variety, had a higher content of procyanidins than clear juices. Radical-scavenging activity was measured by electron paramagnetic resonance (EPR) spectroscopy using the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. All juices showed long-lasting radical-scavenging activity, and EPR spectra were recorded over time to follow the reaction kinetics. Scavenging of DPPH showed pseudo-first-order kinetics, which might be expected in the presence of polymerised antioxidants that prevent closer contact between the DPPH radical and hydroxyl groups. The content of polymeric procyanidins showed a linear dependence on the rate constant, suggesting that these compounds are mainly responsible for time-extended radical-scavenging activity. The antioxidant properties of apple juices were much better reproduced by EPR spectroscopy than by UV–visible measurements. The former method is especially sensitive to the concentration of polymerised or bound procyanidins, whilst the latter method requires transparent (clear) samples. Apple juices, especially cloudy ones, are a rich source of natural antioxidants that may be used in the pharmaceutical or food industry. Copyright © 2006 Society of Chemical Industry
Public awareness of the purported health benefits of dietary antioxidants has increased the demand for fruit and vegetable products with recognized and improved antioxidant quality and has created new opportunities for the horticulture and food industry to improve fruit and vegetable quality by enhancing antioxidant content. This review describes the production and processing factors that influence the content of the major fruit and vegetable antioxidants, namely vitamin C, carotenoids, and phenolics. There is substantial genetic variation in the content of each of these antioxidant types among fruit and vegetable cultivars. Compared with vitamin C and carotenoids, the levels of phenolic antioxidants appear to be more sensitive to environmental conditions both before and after harvest. Although vitamin C can be readily lost during fresh storage, the content of certain carotenoids and phenolics can actually increase during suitable conditions of fresh storage. Vitamin C and phenolics are more susceptible to loss during processing, especially by leaching from plant tissues into processing water. The combination of cultivar variation and responsiveness to specific environmental conditions can create opportunities for the production and processing of fruits and vegetables with improved antioxidant properties.
Infrared (IR) heating provides significant advantages over conventional heating, including reduced heating time, uniform heating, reduced quality losses, absence of solute migration in food material, versatile, simple, and compact equipment, and significant energy saving. Infrared heating can be applied to various food processing operations, namely, drying, baking, roasting, blanching, pasteurization, and sterilization. Combinations of IR heating with microwave heating and other common conductive and convective modes of heating have been gaining momentum because of increased energy throughput. This article reviews aspects of IR heating and presents a theoretical basis for IR heat processing of food materials and the interaction of IR radiation with food components. The effect of IR on food quality attributes is discussed in the context of samples and process parameters. Applications of IR heating in food processing operations and future research potential are also reviewed.
The rate of scavenging of peroxyl radicals and of diphenylpicrylhydrazyl radicals by flavanones, flavones, flavanols and
flavonols commonly occurring in foods was found, when determined by ESR spin trapping and by stopped-flow spectroscopy, respectively,
to be the highest for the most reducing of the flavonoids. Among 12 flavonoids investigated a threshold potential of approximately
+0.4 V seems to exist, above which the flavonoids become ineffective radical scavengers, as determined by ESR spectroscopy
using 5,5-dimethyl-1-pyrroline-N-oxide as spin trap. Scavenging of diphenylpicrylhydrazyl radicals showed (pseudo) first order kinetics for excess of flavonoids,
and the reaction half-life could also be determined for the less effective flavonoids. For kaempferol and eriodictyol, flavonoids
with very similar reduction potentials for their phenoxyl radicals, rate constants for the bimolecular scavenging could be
determined in methanol and had the value (7.0 ±0.7)×102 s−1 M−1 and 33±1 s−1 M−1 at 25°C, respectively, showing that other factors than the driving force, such as hydrophilic/lipophilic balance are important,
as was further confirmed in an oxygen consumption assay based on a linoleic acid emulsion, where decreasing antioxidant efficiency
followed the order: (+)-catechin>(±)-taxifolin≥luteolin>kaempferol>quercetin>>naringenin.
Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol
(30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared
was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTSo−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared
extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed
tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol)
acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically
significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of
Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the
modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e.,
measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTSo− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays.
The antiradical activities of various antioxidants were determined using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH*). In its radical form. DPPH* has an absorption band at 515 nm which dissappears upon reduction by an antiradical compound. Twenty compounds were reacted with the DPPH* and shown to follow one of three possible reaction kinetic types. Ascorbic acid, isoascorbic acid and isoeugenol reacted quickly with the DPPH* reaching a steady state immediately. Rosmarinic acid and δ-tocopherol reacted a little slower and reached a steady state within 30 min. The remaining compounds reacted more progressively with the DPPH* reaching a steady state from 1 to 6 h. Caffeic acid, gentisic acid and gallic acid showed the highest antiradical activities with a stoichiometry of 4 to 6 reduced DPPH* molecules per molecule of antioxidant. Vanillin, phenol, γ-resorcylic acid and vanillic acid were found to be poor antiradical compounds. The stoichiometry for the other 13 phenolic compounds varied from one to three reduced DPPH* molecules per molecule of antioxidant. Possible mechanisms are proposed to explain the experimental results.
Browning reactions represent an interesting research area for the implications in food technology, nutrition and health. The development of some non-enzymatic browning reactions, such as Maillard reaction, has been recently associated to the formation of compounds with strong antioxidant capacity. In this paper, the relation between colour changes due to non-enzymatic browning and the formation of compounds with antioxidant activity is discussed. Simple positive or complex correlation between colour and antioxidant properties can be found depending on composition and technological history of the product. Complex relations between these variables are generally obtained in multi-component and in formulated foods, where the simultaneous development of a number of reactions, interacting or prevailing Maillard reaction itself, can affect in opposite ways the overall antioxidant properties and colour of the product.
Application of combined electromagnetic radiation and hot air is gaining momentum in food processing. A combined infrared and hot air heating system was developed for drying of vegetables. A conveyorised drying system having three chambers was fitted with mid-infrared (MIR) heaters for radiative heating. Through-flow hot air circulation was also provided for convective mode heating. The system was designed to operate under infrared, hot air and combination mode independently. The performance evaluation studies indicated that combination drying of carrot and potato at 80 °C with air at a velocity of 1 m/s and temperature of 40 °C reduced the drying time by 48%, besides consuming less energy (63%) compared to hot air heating. Combination drying also gave better results over infrared heating alone. The energy utilization efficiency of the dryer was estimated to be 38% for both carrot and potato drying.
Low-cost drying technologies suitable for rural farming areas are presented. Some of the important considerations with regard to their suitability include: 1. Low initial capital; 2. easy-to-operate with no complicated electronic/mechanical protocol, and 3. effective in promoting better drying kinetics. The drying technologies that were selected include fluidized bed, spouted bed, infrared, solar, simple convective and desiccant drying. A brief introduction on each drying technology has been presented followed by some technical details on their working operations. Examples of farming crops suitable for the employment of individual drying technology are provided to illustrate their potential application in agricultural product drying.
This paper gives an update of recent developments in the dry conservation of foodstuffs, focusing on fruits and vegetables. Technological progress in microwave and radio frequency assisted drying processes will be presented. The effects of dehydration on product quality will be discussed. As these technological developments are driven by consumer demand for healthy, fresh-like and convenient food, the effects of dehydration will be discussed. Increasingly, the link between the process and product quality can be elucidated by quantifying the mobility of complex food matrices. The role of the glass transition temperature on the quality and shelf-life of dehydrated foods will be described.
Food dehydration is still one of the most relevant and challenging unit operations in food processing, although the art of food preservation through the partial removal of water content dates back several centuries. This article provides essential information on the fundamental, including psychrometry, and applied engineering aspects of food dehydration with up-to-date available commercial applications. The evolution of drying technology, divided into four generations, is thoroughly reviewed, from tray drying to the combination of some drying technologies (the hurdle technology approach in drying) in order to optimize the process in terms of final food quality and energy consumption. The study of each generation covered numerous examples of different dryers, including their principles of operation, basic configurations and most common applications, as well as their main advantages and disadvantages.
A study was conducted to investigate [by high-performance liquid chromatography (HPLC)]the antioxidant vitamin content of paprika during ripening, processing and storage. The most biologically effective antioxidant vitamins, such as ascorbic acid, tocopherols and carotenoids, were separated, identified and quantitated in different samples.The rate of in vivo synthesis of the three antioxidants increased after onset of the ripening process was induced in the climacteric fruits. As ripeness advanced, antioxidant vitamins tended to increase proportionally except that ascorbic acid reached a maximum level at the colour break-II stage and then declined. During drying and storage there was a dramatic decrease in the concentration of tocopherol and ascorbic acid as a result of active antioxidation performance, while carotenoid content decreased at a lower rate.Application of a forced-air drying technique resulted in a significantly high retention of antioxidant vitamins by dried or ground paprika. The different cultivars showed significant differences in their antioxidant vitamin contents.
Drying of food consists of three steps, namely pre-drying processing, dehydration and post-drying handling of the material. The pre-drying processes depend on the physical state of the material subjected to drying. Liquids are vacuum concentrated, treated with enzymes or foamed, while solids are sulfited, soaked in solutions of different compounds, dewatered by osmosis, blanched, frozen or treated by high pressure. Drying of the pre-treated material can be done under vacuum or at atmospheric pressure. Material undergoing drying can be heated by surface heating or by volumetric heating, and it can be stationary or set in motion. Storage stability of a dry material depends on the state at which the drying process is finished. The effect of all these steps on quality of the final product are discussed. It is shown that to design a process of hot air drying a thorough understanding of all the operations affecting quality is needed.
Regular fruit consumption lowers the risk of cardiovascular diseases and certain cancers, which has been attributed in part to fruit-derived antioxidant flavonoids. However, flavonoids are poorly absorbed by humans, and the increase in plasma antioxidant capacity observed after consumption of flavonoid-rich foods often greatly exceeds the increase in plasma flavonoids. In the present study, six healthy subjects consumed five Red Delicious apples (1037 +/- 38 g), plain bagels (263.1 +/- 0.9 g) and water matching the carbohydrate content and mass of the apples, and fructose (63.9 +/- 2.9 g) in water matching the fructose content and mass of the apples. The antioxidant capacity of plasma was measured before and up to 6 h after food consumption as ferric reducing antioxidant potential (FRAP), without or with ascorbate oxidase treatment (FRAPAO) to estimate the contribution of ascorbate. Baseline plasma FRAP and FRAPAO were 445 +/- 35 and 363 +/- 35 microM trolox equivalents, respectively. Apple consumption caused an acute, transient increase in both plasma FRAP and FRAPAO, with increases after 1 h of 54.6 +/- 8.7 and 61.3 = 17.2 microM trolox equivalents, respectively. This increase in plasma antioxidant capacity was paralleled by a large increase in plasma urate, a metabolic antioxidant, from 271 +/- 39 microM at baseline to 367 +/- 43 microM after 1 h. In contrast, FRAP and FRAPAO time-dependently decreased after bagel consumption, together with urate. Consumption of fructose mimicked the effects of apples with respect to increased FRAP, FRAPAO, and urate, but not ascorbate. Taken together, our data show that the increase in plasma antioxidant capacity in humans after apple consumption is due mainly to the well-known metabolic effect of fructose on urate, not apple-derived antioxidant flavonoids.
In this study the main chemical parameters, ascorbic acid and polyphenol content, and antioxidant activity of two varieties of prunes, dried by high-temperature (85 + 70 degrees C) and low-temperature (60 degrees C) procedures, were monitored during storage. Ascorbic acid content was higher in the prunes dried at 60 degrees C but significantly decreased in both varieties during storage. The different classes of polyphenols analyzed (cinnamates, anthocyanins, flavonols) showed different stabilities during storage. Neochlorogenic acid decreased only in the President variety, whereas chlorogenic acid increased in both varieties; anthocyanins, present only in the President prunes, disappeared in the first months of storage, and the flavonol content fell significantly in both cultivars during the year of the study. Drying temperature significantly affected the polyphenol content, with different effects according to the class of polyphenols. Antioxidant activity showed a significant increase at the end of the storage period and in the President variety was higher in the sample dried at the higher temperature.
Apples are an important source of flavonoids in the human diet. The effect of processing apples into juice on polyphenolic antioxidant content and activity is described. Raw juice obtained from Jonagold apples by pulping and straight pressing or after pulp enzyming had an antioxidant activity that was only 10 and 3%, respectively, of the activity of the fresh apples. The levels of flavonoids and chlorogenic acid in the juice were reduced to between 50% (chlorogenic acid) and 3% (catechins). Most of the antioxidants were retained in the pomace rather than being transferred into the juice. Apparently, most of the antioxidant compounds are absorbed to the solid matter of the pomace. In apple juice, 45% of the total measured antioxidant activity could be ascribed to the analyzed antioxidants. For three apple cultivars tested (Elstar, Golden Delicious, and Jonagold), the processing methods had similar effects. The results indicate that processing can have a major impact on the bioactivity of products.
Antioxidant activity and phenolic compound capacity in dried highbush blueberries
- ´ Scibisz
- I Mitek
´ Scibisz, I.; Mitek, M. Antioxidant activity and phenolic compound capacity in dried highbush blueberries (Vaccinum Corymbosum L.). ˙ Zywno´ Technologia Jako´, 4 (49), 68–76 (in Polish).
Convective-microwave drying of apples and carrots
- P P Lewicki
- D Witrowa-Rajchert
- A Sawczuk
Lewicki, P.P.; Witrowa-Rajchert, D.; Sawczuk, A. Convective-microwave drying of apples and carrots. ˙ Zywno´ Technologia Jako´, 2 (27), 28–42 (in Polish).
The effect of drying temperature and storage period of dried parsley leaves on vitamin C content
- W Kmiecik
Kmiecik, W. The effect of drying temperature and storage period of dried parsley leaves on vitamin C content. Bromatology and Toxicology Chemistry 1995, 28 (3), 235–241 (
Fruits with high antioxidant activity as functional foods. In: Functional Food Ingredients and Nutraceuticals: Processing Technologies
- S Y Wang
Wang, S.Y. Fruits with high antioxidant activity as functional foods. In: Functional Food Ingredients and Nutraceuticals: Processing Technologies; Shi, J.; Ed.; Boca Raton, FL: Taylor & Francis Group., LLC, 2006; 371 pp.
Effect of heat treatment on antioxidant content in foods Hydrothermal treatment of dry legume seeds
- M Kulczak
Kulczak, M. Effect of heat treatment on antioxidant content in foods. Hydrothermal treatment of dry legume seeds. In: Przeciwutleniacze w ˙ Zywno´. Aspekty Zdrowotne, Technologiczne, Molekularne i Analityczne; W. Grajek, WNT: Warszawa, Polska, 2007; 441 pp. (in Polish).