Article

Effect of Drying Methods on Chemical Composition, Color and Antioxidant Properties of Thai Red Curry Powder

January 2010
Kasetsart Journal - Natural Science 44(1)

Authors:

Thai red curry pastes were transformed into powder by two different drying methods: microwave and hot-air drying. The microwave drying was carried out in a microwave oven with output powers of 180, 360 and 540 W and the hot-air drying was carried out at air temperatures of 60, 70 and 80°C. The quality attributes of Thai red curry powder were evaluated for proximate composition, color (Hunter L, a and b) and antioxidant properties (total phenolic content and antioxidant activities). The Folin-Ciocalteu method was used to determine total phenolic content, while 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidative power (FRAP) assays were used to elucidate antioxidant activities. The drying methods showed no significant effects on the chemical compositions of the red curry powder, whereas color and antioxidant properties were all affected by the two methods to different extents. Microwave drying resulted in darker and less yellow color than the hot-air drying. Almost all red curry powder in the microwave-dried samples had a greater phenolic content and antioxidant activity than hot-air dried samples.

Total Phenolics, Flavonoids, and Antioxidant Activity of Sage (Salvia officinalis L.) Plants as Affected by Different Drying Methods

Article

Mar 2012

In the current study, we determined the effects of seven drying methods on total phenolics, flavonoids, individual phenolics, and antioxidant activity of the methanol extract of Salvia officinalis L. As compared with total phenolic content (TPC) of fresh plants, results showed that the highest TPC was recorded in plants dried by microwave (MW) at a power of 800 W/30 g of fresh plant and was 4.2 times higher than that of fresh plants whereas the lowest content was found in the case of plants dried by far-infrared (FIR) at 45 °C. The analysis of the different extracts by RP-HPLC showed a predominance of phenolic acids particularly in fresh plants and those dried by MW (600 W/30 g of fresh plant) whereas flavonoids predominate in the case of plants dried by FIR (65 °C). The assessment of the radical scavenging activity (RSA) against the stable radical 1,1-diphenyl-1-picrylhydrazyl (DPPH) showed an increase in the scavenging effect particularly in MW (800 W/30 g of fresh plant) dried plants with an IC50 = 13.49 μg ml−1 (IC50 is the concentration required to cause 50 % DPPH inhibition). The complementary assessment of the RSA using the β-carotene/linoleic acid system showed an increase of this activity for all extracts and particularly for the extract derived from MW (600 W/30 g of fresh plant) dried plants as compared to fresh ones. Finally, all the plant extracts showed moderate reducing power as assessed by the ferric-reducing antioxidant potential. These results suggested that MW drying could be applied to retain phenolic contents and to enhance antioxidant activity of sage plant materials.

Total Phenolics, Flavonoids, and Antioxidant Activity of Sage

Data

Full-text available

Oct 2013

Syzyguim guineense Extracts Show Antioxidant Activities and Beneficial Activities on Oxidative Stress Induced by Ferric Chloride in the Liver Homogenate

Article

Full-text available

Sep 2014

Anatole Constant Pieme

The aim of this study was to determine the in vitro antioxidant activity, free radical scavenging property and the beneficial effects of extracts of various parts of Syzygium guineense in reducing oxidative stress damage in the liver. The effects of extracts on free radicals were determined on radicals DPPH, ABTS, NO and OH followed by the antioxidant properties using Ferric Reducing Antioxidant Power assay (FRAP) and hosphomolybdenum (PPMB). The phytochemical screening of these extracts was performed by determination of the phenolic content. The oxidative damage inhibition in the liver was determined by measuring malondialdehyde (MDA) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase. Overall, the bark extract of the ethanol/water or methanol showed the highest radical scavenging activities against DPPH, ABTS and OH radicals compared to the other extracts. This extract also contained the highest phenolic content implying the potential contribution of phenolic compounds towards the antioxidant activities. However, the methanol extract of the root demonstrated the highest protective effects of SOD and CAT against ferric chloride while the hydro-ethanol extract of the leaves exhibited the highest inhibitory effects on lipid peroxidation. These findings suggest that antioxidant properties of S. guineense extracts could be attributed to phenolic compounds revealed by phytochemical studies. Thus, the present results indicate clearly that the extracts of S. guineense possess antioxidant properties and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants. The antioxidant properties of the bark extract may thus sustain its various biological activities. Keywords: antioxidant activity; phenolic content; Syzygium guineense; radical scavenging activity; lipid peroxidation

Syzyguim guineense Extracts Show Antioxidant Activities and Beneficial Activities on Oxidative Stress Induced by Ferric Chloride in the Liver Homogenate

Article

Full-text available

Sep 2014

OPTIMIZATION OF HOT-AIR AND MICROWAVE DRYING PROCESS PARAMETERS FOR EVALUATION OF PHENOLICS AND ANTIOXIDANT ACTIVITY IN SLICED WHITE BUTTON MUSHROOM (Agaricus bisporus) USING RESPONSE SURFACE METHODOLOGY

Article

Apr 2021

This study was conducted to investigate hot-air and microwave dryings on phenolics and antioxidant activity of dried white button mushroom slices (Agaricus bisporus) using the response surface methodology. It was also aimed to determine optimized drying conditions. In hot-air drying, total phenolics content reduced with corresponding increase in drying temperature and slice thickness, whereas in microwave drying, the total phenolics content increased with microwave power. Although the effect of drying temperature on antioxidant activity is not significant, there is a decrease in antioxidant activity as the slice thickness of the samples increases. Microwave power had also a significant linear effect on antioxidant activity of dried samples (p<0.01). Both increases and decreases in individual phenolic compounds were detected with the change of drying conditions and sample thickness. A quadratic model was well fitted to all responses. As a result of numerical optimization, optimum conditions for hot-air drier and microwave oven were suggested as 50 °C and 600 Watt having mushroom slices of 2 mm thickness, respectively. Our results show that the quality of dried mushroom depends on the drying method and conditions. Also, microwave drying is suitable method for drying of mushroom slices within a shorter time compared with hot-air drying.

Drying Characteristics of Lemon By-product (Citrus limon. v. lunari): Effects of Drying Modes on Quality Attributes Kinetics’

Article

Full-text available

Jan 2020

The aim of this work is to establish a comparative investigation of the effect of different drying processes: microwave dehydration (100–600 W), air drying (40–60 °C) and infrared drying (40–60 °C) on drying kinetics and on the main quality attributes (color, total phenols and flavonoids contents, water and oil retention capacities) kinetics’ of lemon (Citrus limon. v. lunari) peels. The experimental drying kinetics’ of lemon peels were fitted to nine thin layer drying models. The Midilli and Kucuk model showed a better fit to experimental drying data for the three drying processes. Microwave drying at 450W preserved the maximum phenols (1.855 ± 0.016 g CAE/100 g DM) and flavonoids (0.802 ± 0.072 g RE/100 g DM) contents respectively. An increase of phenol content was noticed after 9, 13 and 14 min of microwave drying at 600, 450 and 300 W and after 156, 102 and 54 min of infrared drying at 40, 50 and 60 °C. A first-order kinetic model adequately fitted, at the beginning of drying processes, the change of total phenols and flavonoids contents. Total color difference (ΔE) increased progressively with increasing drying time and temperature or microwave power level. ΔE showed a zero-order model whatever the applied drying process. Water retention capacity (WRC) of dried lemon peels decreased during drying processes. However, infrared and microwave drying increased the oil retention capacity (ORC) of lemon peels. The WRC and ORC followed first-order kinetics during air drying and a second order polynomial model during microwave and infrared drying processes.

Bioactive compounds’ contents, drying kinetics and mathematical modelling of tomato slices influenced by drying temperatures and time

Article

Full-text available

Mar 2017

This study investigated the influence of drying temperature, and time on antioxidant activity, phenolic, flavonoid, lycopene and β – carotene contents of tomato slices. It also evaluated the influence of drying process on drying kinetics, moisture diffusivity and activation energy. Oven processed tomato slices had temperature-dependent significant increase in antioxidant activity at 30 and 60 min, phenolic from 30 - 120 min and lycopene contents from 120 - 300 min. Significantly decreased contents of flavonoid and β – carotene were obtained for oven processed tomato slices with increasing drying temperature and time. Page model accurately predicted the drying process of tomato slices. Similarity between experimentally determined moisture ratio and Page predicted moisture ratio was obtained with high correlation (R² = 0.9986). Effective moisture diffusivities indicated that drying process of tomato slices was temperature dependent while Arrhenius equation explained the relationship between activation energy and temperature.

MİKRODALGA-VAKUM KOMBİNE KURUTMA YÖNTEMİNİN KUŞBURNUNUN KALİTE ÖZELLİKLERİ ÜZERİNE ETKİSİNİN İNCELENMESİ

Thesis

Aug 2019

Mahir Cin

Drying is a preservation process commonly used in the food industry. Today, hot-air drying is commonly used to preserve products that do not have a long shelf life such as fruit and vegetables. However, considering the quality losses and long drying times of the final products dried by this method, new drying techniques have started to be used recently. In this study, it was aimed to investigate the effect of microwave-vacuum drying (<10% moisture content) on the drying time characteristic and some quality properties of rosehip. In accordance with this purpose, the drying process was performed under different microwave power (50, 100, and 150 W) and absolute pressures (40, 75 and 110 mbar). Power and pressure effects on quality characteristics were determined. Freeze drying and hot air drying (60 ° C-1.5 m / s) methods were also investigated. The effect of three drying methods on some chemical and physical quality characteristics of dried rose hip was determined and compared. The drying time to the target moisture content by microwave-vacuum method is 75-195 minutes. The shortest drying time was observed under high power and low absolute pressure conditions. In all chemical analysis results (total phenolic content, total antioxidant activity amount and ascorbic acid amount), the lowest value was found in hot-air dried samples. Dried samples with hot-air were found to have the lowest value in all chemical analysis results (Total phenolic content, total antioxidant activity amount and ascorbic acid amount). Total phenolic content was highest in all microwave-vacuum dried samples. Most of the microwave vacuum dried samples had higher total antioxidant activity amount than freeze-dried samples. However, the highest amount of ascorbic acid (vitamin C) was obtained in freeze-dried samples after fresh sample. While the dried samples with Microwave-vacum and freeze drying had a similar open and porous microstructure, the dried samples with hot-air had a completely closed and non-porous structure. Therefore, the rehydration rate values of microwave-vacuum and freeze drying samples were higher than those of hot-air samples. At high microwave powers (150 W) and freze drying dried samples were found rehydration rate was highest and there was no statistically significant difference between them.

Effects of drying conditions in low‐temperature microwave‐assisted drying on bioactive compounds and antioxidant activity of dehydrated bitter melon (Momordica charantia L.)

Article

Full-text available

Jun 2020

Bitter melon (Momordica charantia L.) is a fruit that brings health benefits to consumers because the fruit is rich in bioactive compounds. In this work, a combination of low‐temperature convective drying and microwave radiation was used to dehydrate sliced bitter melon. One‐factor‐at‐a‐time design was performed to evaluate the influence of microwave power density (1.5, 3.0, 4.5 W/g), drying temperatures (20, 25, and 30°C), and air velocity (1.0, 1.2 and 1.4 m/s) on the change of moisture content, nutrient levels (vitamin C and total phenolics), and the antioxidant activities (DPPH and FRAP assays) of the bitter melon. The obtained results showed that all investigated factors affected the rate of moisture removal. Microwave power density output and air‐drying temperature strongly participated in the retention of nutrients. In this study, the drying process was driven by both heat and mass transfer processes, so the increase of air velocity prolonged the drying time causing more loss of nutrient levels and antioxidant activities. It was found that DPPH free radical scavenging ability directly correlated with total phenolic content, but the ferric‐reducing antioxidant power was related to the presence of reductants including phenolic compounds, vitamin C, and other phytochemicals in bitter melons. This work determined that microwave power density and the air‐drying temperature are the main two factors that should be used for further investigations. The effects of drying conditions in the convective low‐temperature microwave‐assisted drying of bitter melon were investigated. The results were used to develop an understanding of how the microwave power density, drying temperature, and air velocity affect the final quality of the dried fruit product.

Effect of Agronomic Practices and Drying Techniques on Nutritional and Quality Parameters of Onions ( Allium cepa L.)

Article

May 2017
DRY TECHNOL

The effects of four drying treatments (freeze-drying, hot air-drying, oven drying and vacuum oven drying) on the bioactive compounds (total phenolics, total flavonoids and quercetins), colour and antioxidant capacity of organic and non-organic onions of two varieties (Red Baron and Hyfort) subjected to two agronomic treatments (OSOP and CSCP) were investigated. The average final dry weight of the samples was 9.82 ±0.41 %. After drying, there was a significant increase in total phenolics, total flavonoids, total quercetin and antioxidant capacity in comparison with fresh onion samples, which suggested that drying can improve the extractability of phenols and accordingly the antioxidant activity of onions. Different drying techniques also resulted in different fractions of individual quercetins. Dried organic onions had higher levels of bioactive compounds and antioxidant capacity than dried non-organic onions for a same variety. The highest antioxidant capacity displayed by freeze-dried and hot air-dried organic Red Baron onion is in agreement with their higher phenolic and flavonoid contents compared to all other samples.

Effect of Drying on Quality and Sensory Attributes of Lemongrass (Cymbopogon Citratus) Tea

Article

Full-text available

Feb 2018

The aim of this study was to investigate the effect of drying on quality and sensory attributes of lemon grass (Cymbopogon citratus) tea. Lemongrass (C. citratus) leaves were dried using four different drying methods: sun, solar, oven (40, 50, and 60°C), and microwave (50 W). Teas made from the grass were analyzed for colour, pH and sensory attribute. Data obtained were statistically analyzed using SPSS Version 23 one way analysis of variance and means were compared using Duncan multiple comparison test (p ˂ 0.05). Results obtained indicate that after drying the moisture content were significantly reduced. Ash content results showed no significant difference amongst lemongrass samples dried under difference drying methods. However, there was a significant difference (p < 0.05) in the pH of tea made from the lemongrass dried under different drying methods. Results indicate that drying temperature and time are the main factors affecting the colour of dried lemongrass leaves for tea. There was a significant difference (p < 0.05) in the colour profile of the dried leaves. Sensory evaluation results showed that the colour, aroma, taste, and overall acceptability scores of tea from lemongrass dried with oven at 40°C was highest. The study revealed that oven drying at 40°C for 15 hours was found to be most suitable for drying of lemongrass leaves for tea production in order to retain appreciable sensory attributes.

Effect of oven and microwave drying on phenolic compounds and antioxidant capacity of coriander leaves

Article

Full-text available

May 2017

In the present study, the effects of two drying methods on antioxidant properties of coriander leaves were investigated. For the rate of drying, results showed that sample weight stability was reached faster in microwave (900 W/70 s) than in oven drying (120°C/290 s). Concerning antioxidants, results showed that the highest total polyphenols and total flavonoids contents were recorded by leaves dried in microwave (48.44 mg GAE/g and 20.28 mg RE/g, respectively) than those dried in oven (26.64 mg GAE/g and 19.60 mg RE/g, respectively). At the end, the assessment of radical scavenging activity against stable radical ABTS and DPPH showed an increase in scavenging effect particularly when microwave technology was used.

Drying kinetics, colour, total phenolic content and antioxidant capacity properties of kiwi dried by different methods

Article

Full-text available

Mar 2017

This study analysed the convective (60, 70 and 80° C), microwave (120 and 350 W) and freeze drying methods in terms of their effects on the drying characteristics, colour, total phenolic content (TPC) and antioxidant capacity of kiwi slices. Nine different mathematical models were applied to experimental data to achieve the most accurate calculation for drying curves. The Midilli et al. and Wang and Singh models proved to be the most suitable at explaining the drying kinetics of kiwi samples as compared to other models according to the statistical tests. Each drying method was significantly affected by colour parameters (L*, a*, b*, C, α and ΔE). The dried samples exhibited respectively 5–49 % and 10–47 % less TPC and antioxidant capacity compared to the fresh sample. According to the correlation analysis conducted between TPC and antioxidant capacity for kiwi slices, there is a positive correlation (R2 = 0.7796). Microwave dried samples at 120 W particularly had the lowest TPC and antioxidant capacity. Freeze drying method yielded the closest values with respect to colour values, total phenol content and antioxidant capacity to those of fresh samples when compared to the other methods.

Functional Properties of Curry Paste in Relation to Digestibility and Fermentation by Gut Microbiota

Article

Apr 2017

The prebiotic properties of sour curry paste in the upper gut and the gut microbiota were investigated in vivo during digestion. The effect of the addition of garcinia as souring agent in curry paste was studied. Curry paste without garcinia (P1) and curry paste with garcinia (P2) increased the number of beneficial bacteria in the gut microbiota, especially bifidobacteria and lactobacilli, and significantly (p<0.05) decreased the number of harmful bacteria (Clostridia). Fecal fermentation with P1 resulted in a prebiotic index (PI) of 1.19, whereas fermentation with P2 resulted in a PI of 2.75. The fermented metabolites produced were lactic acid; vitamins; and short-chain fatty acids (SCFAs) such as acetic acid, propionic acid and butyric acid. P1 produced metabolites including lactic acid, SCFAs and B vitamins in higher amounts than P2. After a 24 h fermentation period with colonic microbiota, P1 produced vitamins B1 (18.38 ± 0.10 µg/ml) and B2 (45.28 ± 2.02 µg/ml) but not folic acid, whereas P2 produced only vitamin B1 (5.99 ± 0.48 µg/ml).

Effects of Drying Conditions on Physicochemical and Antioxidant Properties of Banana ( Musa cavendish ) Peels

Article

Oct 2016

A significant amount of banana peels is generated as waste annually and shows great potential as a lead material for further utilisation in the nutraceutical industry. However, potentiality of banana peel utilization largely depends on the favourable drying condition of the material before it can be used for further processing. Therefore, it is necessary to identify the suitable drying conditions for banana peel. This study investigated the effect of six different drying methods on the quality of banana peels. The results showed that different drying conditions significantly affected the physical, chemical and antioxidant properties of dried peels. Microwave irradiation at the power level of 960 W for 6 min was the most suitable condition, as these dried peels had good physical properties, minimum loss of bioactive compounds and antioxidant properties. This was followed by freeze drying, vacuum oven at 60 °C, hot air oven at 120 °C, dehumidified air at 60 °C and sun drying. The peels dried by microwave possessed a total phenolics content of 25.26 mg GAE/g DM and potent antioxidant capacity (DPPH of 37.70; ABTS of 46.35; FRAP of 45.94, and CUPRAC 64.55 mg TE/g DM). Therefore, the study recommends the use microwave irradiation under the studied condition (power level of 960 W for 6 min) for further processing and utilisation.

Optimization of microwave vacuum drying parameters for germinated lentils based on starch digestibility, antioxidant activity and total phenolic content

Article

Apr 2017

The aim of this study was to optimize the processing parameters of pulse mode microwave-vacuum drying of germinated green and red lentils (CDC Greenland and CDC Maxim) and investigate the changes in their total phenolic content (TPC), total antioxidant activity (TAA) and In-vitro starch digestibility (SD). The lentils were germinated for 5 days and dried by a pulse mode microwave-vacuum method, using 2 s to 8 s out of 10 s pulsed mode at 2000W microwave power and varying the vacuum pressure level between 15 and 45 kPa. In-vitro starch digestibility increased significantly with increased microwave power level. The TPC and TAA appeared to vary distinctively in the two varieties of selected lentils. Vacuum pressure levels did not significantly (p > 0.05) affect any responses. Green lentils could be dried at 8 s microwave power and 45 kPa vacuum pressure and red lentils could be dried at 5.5 s microwave power and 42.19 kPa vacuum pressure. The microwave-vacuum drying showed great potential for the drying of germinated lentils.

Effects of drying process on total phenolics, antioxidant activity and flavonoid contents of common mediterranean herbs

Article

Full-text available

Jan 2015

Four different fresh and dried herb species (sage, thyme, mint and lemonbalm) were evaluated to study the effect of drying process on the total phenolics, antioxidant activity, flavonoid contents and color properties. Fresh mint had the highest contents of total phenolics (335.4 mg GAE/100 g), whereas lower levels were respectively found in sage (316.4 mg GAE/100 g) followed by lemonbalm (303.2 mg GAE/100 g) and thyme (299.2 mg GAE/100 g). Dry processing significantly decreased the phytochemical contents of all investigated herbs. Compare to air drying, total phenolics, antioxidant activity and flavonoids content in herbs decreased apparently by oven dried. Fresh mint had the highest antioxidant activity (87.46%) and flavonoids content (298.51 mg CE/100 g), while the fresh sage, thyme and lemonbalm were found to have antioxidant activity values of 86.81%, 86.56% and 85.26%, respectively. Results showed that air drying herbs contained more total phenolics, antioxidant activity, and flavonoids than oven drying herbs.

Polyphenol Oxidase Inactivation by Microwave Oven and Its Effect on Phenolic Profile of Loquat ( Eriobotrya japonica ) Fruit

Article

Full-text available

Jan 2013
FNS

The objective of this research was investigated the effect of polyphenol oxidase microwave treatment on phenolic composition, antioxidant activity and microstructure of loquat fruit. Phenolic profile of methanolic extracts prepared from fresh, and microwave-treated samples were analyzed. Antioxidant activity was also evaluated by 2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS •+ ) and 1,1-diphenyl-2-picrylhydrazyl (DPPH + ) methods. In addition, polyphenol oxidase inactivation was carried out using a response surface methodology to establish the optimal conditions of treatment. The phenolic content of fresh mesocarp was 311 ± 0.60 mg gallic acid equivalents (GAE)/100g dry weight (DW) and that of microwave-treated mesocarp was 1230 ± 0.36 mg GAE/100g DW. Total phenolic content of water/ methanol extract significantly increases after microwave treatment rather than methanolic extract of fresh loquat. Five glycoside phenolics were identified by HPLC-DAD-MS as 3-caffeoylquinic acid, 3-p-coumaroylquinic acid, 5-caffeoylquinic acid and quercetin-3-O-sambubioside. Methanolic extract of microwave-treated mesocarp showed higher antioxidant activity than that of fresh mesocarp. Thus, polyphenol oxidase inactivation by microwave energy preserved the integrity of phenolic compounds as well as antioxidant activity in mesocarp extracts prepared from loquat fruit. It was also noted that phenolics were more abundant in the microwaved samples than in the fresh samples.

Effect of drying and storage on bioactive components of jambhul and wood apple

Article

Full-text available

Mar 2014

Jambhul and wood apple were subjected to two different drying methods to examine the effect of drying temperatures (80 °C and 60 °C) and influence of storage conditions viz., room temperature (25 °C) and refrigeration temperature (4 °C) on bioactive constituents of jambhul and wood apple powder for 90 days. Results showed that retention of phenolics, ascorbic acid and antioxidant capacity such as ABTS, DPPH and FRAP in jambhul and wood apple were high at 80 °C as compared to 60 °C in both tray and IR drying. Anthocyanin and flavonoid significantly (p<0.05) decreased at 80 °C. Jambhul showed retention of 30.83 %TPC, 10.40% TFC, 9.31 %, TMAC, 12.75 % ascorbic acid, 19.26 % ABTS activity, 98.71 % DPPH activity, and 27.78 % FRAP activitys in IR drying; whereas wood apple showed more retention of 25.74 % TPC, 61 % ascorbic acid, 10.31 % ABTS, 36.45 % DPPH and 0.27 % FRAP in tray drying (TD). During storage bioactive constituents in jambhul powder were preserved at refrigeration temperatures whereas in wood apple they were retained at room temperature.

Effect of different drying methods on drying characteristics, colour, total phenolic content and antioxidant capacity of Goldenberry (Physalis peruviana L.)

Article

Full-text available

Jan 2014
INT J FOOD SCI TECH

In this study, the effects of convective, microwave and microwave–convective drying methods on the drying characteristics, colour, total phenolic content and antioxidant capacity of goldenberry fruits were investigated. To select the most appropriate thin-layer drying model for drying treatments, nine mathematical drying models were fitted to the experimental data. Based on the statistical tests used for evaluation, the Midilli et al. and Wang and Singh models were considered the best models to describe the drying behaviours of goldenberry fruits in all drying methods. The colour values (L*, a* and b*) of fresh fruit were decreased by drying. Compared with the fresh sample, the dried samples exhibited a 64–75% and 65–75% decrease in total phenolic content and antioxidant capacity, respectively. Among the different drying treatments, the values closest to those of fresh samples with respect to colour values, total phenolic content and antioxidant capacity were achieved with the 160 W microwave drying method.

Effect of oven and microwave drying on polyphenols content and antioxidant capacity of herbal tea from strobilanthes crispus leaves

Article

Full-text available

Jun 2018

Objective: This study aimed to evaluate the effect of oven and microwave drying on total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity of unfermented and fermented tea developed from Strobilanthes crispus leaves.Methods: TPC and TFC were estimated using a spectrophotometric method, while antioxidant capacity was determined using ferric reducing antioxidant power assay and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Camellia sinensis (tea plant), that is, used for the production of all varieties of commercial tea and fresh S. crispus leaves were served as controls in this study.Results: The highest antioxidant activity and TPC were observed in S. crispus tea developed from microwave-dried leaves, while the highest TFC was observed in oven-dried tea. Unfermented S. crispus tea showed significantly higher values (p<0.05) for antioxidant activity, TPC, and TFC as compared to fermented S. crispus tea. A strong and moderate correlation was observed between antioxidant activity and TPC as well as TFC values.Conclusion: The present work clearly showed that S. crispus tea developed from microwave-dried leaves able to preserve the polyphenols and hence contribute to excellent antioxidant capacity. Incorporation of unfermented S. crispus tea in the diet can be a good source of natural antioxidant.

Study on the effect of intermittent microwave drying conditions on the bioactive compounds and antioxidant capacity of beetroots

Article

Full-text available

Feb 2022

The object of this research was the beetroots prepared by intermittent microwave drying at different conditions. The paper aimed to investigate the influence of intermittent microwave drying conditions (power density, microwave gap ratio and slice thickness) on the bioactive compounds and antioxidant capacity of beetroots. A microwave drying system SAM-255 (CEM Corporation, USA) was used to intermittent microwave drying of fresh beetroots. The effect of different power densities (1.0, 1.5, 2.0, and 2.5 W/g), microwave gap ratios (1, 2, 3, and 4) and slice thicknesses (2, 4, 6, and 8 mm) on the bioactive compounds and antioxidant capacity of beetroots were investigated. Colorimetric methods were used to determine contents of betalains, total phenolic and total flavonoid, and antioxidant capacity of dried beetroots. The ascorbic acid content was determined using 2,6-dichloroindophenol titration method. Results showed that power density, microwave gap ratio and slice thickness significantly affected the drying time, bioactive compounds and antioxidant capacity of beetroots. The drying time decreased with the increasing of power density, while increased significantly with the growth of slice thickness and microwave gap ratio. The shortest drying time (35.4±2.6 min) of beetroots was occurred at microwave gap ratio of 2. The content of betacyanins was found to be the highest in the dried beetroots with thickness of 2 mm. The beetroots with slice thickness of 2 and 4 mm showed the highest betacyanins content. Moreover, the highest content of ascorbic acid (240.00±2.32 mg/100 g) and total flavonoid (14.52±0.06 mg rutin equivalent (RE)/g) was appeared at power density of 2.0 W/g, while the content of total phenolic to be highest (12.54±0.13 mg gallic acid equivalent (GAE)/g) at slice thickness of 6 mm. For the antioxidant capacity of dried beetroots, the 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity reached to the highest value of 6.43±0.03 mg trolox equivalent (TE)/g at power density of 2.5 W/g. While the highest values of ferric-reducing antioxidant power (FRAP) (15.47±0.10 mg TE/g) and 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity (25.31±0.30 mg TE/g) at microwave gap ratio of 2. It was found that ABTS radical scavenging ability and FRAP were related to the presence of reductions including betalains, ascorbic acid, and total flavonoid in beetroots. The most effective condition for intermittent microwave drying of beetroots were microwave gap ratio of 2, power density of 2.0 W/g, and slice thickness of 4 mm, leads to a better preservation of bioactive compounds and high antioxidant capacity.

Influence of different microwave-assisted drying methods on the physical properties, bioactive compounds and antioxidant activity of beetroots

Article

Full-text available

Feb 2022

The objective of this study was to investigate the effects of different microwave-assisted drying methods on the physical properties, bioactive compounds and antioxidant activity of beetroots. Beetroots were subjected to high-power microwave drying followed by low-power microwave drying (HMD+LMD), high-power microwave drying (HMD), low-power microwave drying (LMD), high-power microwave drying followed by hot air drying (HMD+HAD), hot air drying followed by low-power microwave dry�ing (HAD+LMD), high-power microwave drying followed by vacuum drying (HMD+VD), and vacu�um drying followed by low-power microwave drying (VD+LMD). The drying time, moisture content, hard�ness, color, microstructure, betalains, ascorbic acid, total flavonoids, 2,2′-azino-bis-(3-ethylbenzоthiazo�line-6-sulfonic acid) (ABTS) radical scavenging activ�ity and ferric reducing antioxidant power (FRAP) of beetroots were analyzed. The shortest drying time (67.0 min) was observed in HMD, while VD+LMD required the longest drying time of 308.0 min. There was no significant difference in the moisture content of dried beetroots prepared by different microwave-assisted drying methods. Beetroots dried by HMD+HAD showed the highest hardness of 1332.0 g, VD+LMD led to the most desirable color with the lowest total color change. Porous structures were found in beetroots pro�duced by HMD+LMD, HMD and LMD. Beetroots pre�pared by VD+LMD displayed the highest content of betacyanin, betaxanthin and total flavonoids. While beetroots dried by HMD illustrated the highest ascor�bic acid content of 272.3 mg/100 g dry weight (DW). In terms of antioxidant activity, the highest FRAP value of beetroots obtained using VD+LMD was 14.95 mg trolox equivalent (TE)/g DW. Meanwhile, beetroots dried by VD+LMD exhibited the largest ABTS radical scavenging activity (16.92 mg TE/g DW). Compared to other microwave-assisted drying methods, VD+LMD is a more promising method for drying beetroots

Effect of sodium carbonate solution pretreatment on drying kinetics, antioxidant capacity changes, and final quality of wolfberry (Lycium barbarum) during drying

Article

Sep 2018
LWT-FOOD SCI TECHNOL

Bioactive compounds and antioxidant activity of beetroots prepared by different drying methods

Article

Full-text available

Dec 2021

Introduction. The aim of the research is to investigate the influence of different drying methods, including freeze drying, vacuum drying, microwave drying and microwave vacuum drying, on the bioactive compounds and antioxidant activity of beetroots. Materials and methods. Bioactive compounds and antioxidant activity of dried beetroots prepared by freeze drying (FD), vacuum drying (VD), microwave drying (MD), and microwave vacuum drying (MVD) were investigated. Moisture analyzer was used to determine moisture content of beetroots. Beetroot powder was extracted three times with 50% ethanol (v/v). Colorimetric methods were used to determinate contents of betalain, ascorbic acid and total phenolic, and 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP) and 2,2′-azino-bis-(3- ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity of dried beetroots. Results and discussion. Drying methods significantly affected the drying time, bioactive compounds and antioxidant activity of beetroots. The shortest drying time (0.56±0.01 h) was occurred at MVD, while FD required the longest drying time of 29.67±0.58 h. There was no significant difference in the final moisture content of dried beetroots prepared by different drying methods. It was found that the dried beetroots prepared by VD showed the highest ascorbic acid content of 8.73±0.23 mg/g, and the beetroots dried by FD displayed the highest betaxanthin content of 2.57±0.01 mg/g, while the beetroots obtained by MD showed the lowest betacyanin content of 2.98±0.02 mg/g, and FD led to significantly lower total phenolic content of beetroots in comparison with other drying methods. In terms of antioxidant activity, the beetroots prepared by MD and MVD showed significantly higher DPPH radical scavenging activity than the beetroots prepared by VD and FD. Meanwhile, the beetroots obtained by VD exhibited the largestABTS radical scavenging activity of 17.22±0.35 mg trolox equivalent (TE)/g. Besides, the beetroots prepared by MVD displayed the highest FRAP value of 13.36±0.17 mg TE/g. Compared to beetroots prepared by other drying methods, the beetroots prepared by FD showed the lowest FRAP, DPPH and ABTS values, indicating the weakest antioxidant activity. Conclusions. Considering the drying time, bioactive compounds and antioxidant activity, MVD is recommended to prepare dehydrated beetroots, which can reduce drying time and better preserve bioactive compounds and antioxidant activity of beetroots.

Toasted yerba mate: Impact of drying methods on bioactive compounds, antioxidant capacity, and mate tea consumer acceptance

Article

Sep 2021
J FOOD PROCESS PRES

This work investigates the consumer's acceptance of hot and iced mate tea, bioactive compounds content and antioxidant capacity of toasted yerba mate leaves dried from various processes, aiming at presenting drying alternatives to the traditional, and mostly used, methods. Therefore, five drying methods were tested, traditional rotary dryer, conveyor dryer and three alternatives including microwave oven, over dryer at 40, 60, 80 °C and freeze-drying, which was followed by toasting. Overall, the microwave oven and freeze dryer were highly efficient and can be considered as drying alternatives with high values of total phenolic compounds (78.72 mg GAE.g-1), antioxidant capacity by DPPH/ABTS (376.6 TEAC µmol.g-1 /1062.04 TEAC µmol.g-1), caffeine (13.25 mg.g-1) and caffeoylquinic acids (69 mg.g-1). Using a reworked python script, the preference map of teas dried in microwave oven and freeze-drying resulted in similar sensory acceptance for hot tea, produced using traditional drying methods, with a slight decrease for the iced tea. Novelty Impact statement The tea industry can adopt microwave and freeze drying as alternative methods for drying mate leaves, this is followed by toast in order to obtain the commercial tea. These methodologies present smaller equipment sizes and removes the dangerous traditional process known as "zapeco". The microwave and freeze drying have a small decrease in sensory acceptance compared to traditional methods used in agri-food industry but with high content of total phenolic compounds, caffeoylquinic acids and high antioxidant activities; also, in the case of microwaves, this method has the advantage of reducing the drying time.

Optimization of Phenolic Compound Recovery and Antioxidant Activity of Bay Leaves Using Sequential and Response Surface Methodologies

Article

Sep 2021

Background The laurel is a shrub native to the Mediterranean basin. It is too often wrongly relegated to the kitchen as a simple condiment while it possesses many therapeutic properties and virtues. The valorization of this plant in terms of bioactive compounds seems to be important. Objective The aim of the present study is to optimize total phenolic content (TPC) extraction and antioxidant activity from dried bay leaves using conventional process and response surface methodology (RSM). Method The study of optimization was firstly tested three extraction methods (maceration, ultrasonic-assisted extraction (UAE), and Microwave-assisted extraction (MAE)) then the best one was considered for RSM. Results The results for the sequential procedure indicated that MAE was the best method for TPC extraction and antioxidant activity of Laurus nobilis leaves. The mathematical modeling of MEA using response surface methodology showed that optimal conditions for phenolic compounds extraction were 57% methanol with microwaves power of 602W during 3.48 minutes. These conditions allowed TPC extraction of 83.53 mg/g and manifested an antioxidant activity of 32.51 mg EAG/g. Conclusion The validation of models indicated that experimental values were in accordance with predicted ones, demonstrating the suitability of developed models and the success of RSM in the optimization of antioxidants extraction from Laurus nobilis leaves. Therefore, the bay leaves could be considered as an interesting source of phenolic antioxidants.

In vitro antioxidant and antibacterial activities of phenolic and alkaloid extracts of Laurus nobilis

Article

Full-text available

May 2021

Laurus nobilis one of medicinal and aromatic plant endemic to the Mediter-ranean region. It is highly appreciated for the condiment benefits of its leaves. Due to its richness in bioactive compounds, the leaves are also used in traditional therapy to treat several infectious diseases. Phenolic com-pounds and alkaloids are particularly important because they are used in many pharmaceutical, food supplement, and cosmetic fields. The presence of phenolic compounds and alkaloids in L. nobilis leaves attracted our atten-tion due to their various functions such as antioxidant capacity and antibac-terial properties. The main objective of this study was to determine antioxi-dant and antibacterial activities of phenolic and alkaloid extracts of L. nobilis. The quantification of antioxidant substances allowed obtaining phenolic compounds content of 86.46 EAG mg/g and a total alkaloids yield of 700 μg/g. The results of antioxidant activity show that, although the alkaloid concen-trations are low, their antioxidant power is higher than phenolic compounds. The results of antibacterial activity of L. nobilis extracts revealed that the highest inhibition was recorded for alkaloid extract against staphylococcal strains responsible for food poisoning. However, L. nobilis phenolic com-pounds showed better activity against phytopathogenic strains associated particularly with potato rot.

Physico-chemical aspects of Thai fermented fish viscera, Tai-Pla, curry powder processed by hot air drying and hybrid microwave-infrared drying

Article

Full-text available

Jun 2021
PLOS ONE

The objective of this research was to comparatively investigate the effect of hot air drying (HA) and hybrid microwave-infrared drying (MI) on physico-chemical characteristics of Thai fermented fish viscera, Tai-Pla , curry powder (TCP). HA was carried out at 60°C, 70°C, and 80°C and MI was carried out at a microwave power of 740, 780, and 810 W with a constant infrared heating power (500 W) for different drying times to obtain the final moisture content ≤ 12.0% and the water activity (a w ) ≤ 0.6. The quality characteristics of TCP were governed by HA temperature and MI output power. TCP dried using HA and MI at all conditions had similar contents of protein, lipid, ash, fiber, and carbohydrate (p>0.05). The fastest drying rate was detected when MI at 810 W for 40 min was applied (p < 0.05). In this condition, TCP had the lowest browning index (A 294 and A 420 ) and the highest lightness ( L* value) (p < 0.05). TCP dried with MI at all powers had higher phenolic content and lower TBARS compared to HA (p < 0.05). However, no significant differences in DPPH • scavenging activity were observed among TPC made by HA and MI (p>0.05). Similar Fourier transform infrared (FTIR) spectra with different peak intensities were observed in all samples, indicating the same functional groups with different contents were found. The bulk density of all TCP ranged from 0.51 g/mL to 0.61 g/mL and the wettability ranged from 24.02% to 26.70%. MI at 810 W for 40 min effectively reduced the drying time (5-fold faster) and lowered the specific energy consumption (18-fold lower) compared to the HA at 60°C for 210 min. Therefore, MI is a promising drying technique to reduce the drying time and improve the overall quality of TCP.

In vitro antioxidant and antibacterial activities of phenolic and alkaloid extracts of Laurus nobilis

Article

Full-text available

May 2021

Laurus nobilis is one of medicinal and aromatic plant endemic to the Mediter-ranean region. It is highly appreciated for the condiment benefits of its leaves. Due to its richness in bioactive compounds, the leaves are also used in traditional therapy to treat several infectious diseases. Phenolic compounds and alkaloids are particularly important because they are used in many pharmaceutical, food supplement, and cosmetic fields. The presence of phenolic compounds and alkaloids in L. nobilis leaves attracted our attention due to their various functions such as antioxidant capacity and antibac-terial properties. The main objective of this study was to determine antioxi-dant and antibacterial activities of phenolic and alkaloid extracts of L. nobilis. The quantification of antioxidant substances allowed obtaining phenolic compounds content of 86.46 EAG mg/g and a total alkaloids yield of 700 µg/ g. The results of antioxidant activity show that, although the alkaloid concentrations are low, their antioxidant power is higher than phenolic compounds. The results of antibacterial activity of L. nobilis extracts revealed that the highest inhibition was recorded for alkaloid extract against staphylococcal strains responsible for food poisoning. However, L. nobilis phenolic compounds showed better activity against phytopathogenic strains associated particularly with potato rot.

In vitro antioxidant, anticholinesterases, anti-α-amylase, and anti-α-glucosidase effects of Algerian Salvia aegyptiaca and Salvia verbenaca

Article

Full-text available

Nov 2020
J FOOD BIOCHEM

In this study, Salvia aegyptiaca and Salvia verbenaca aerial part decoction and methanol extracts (SAE DE, SAE ME, SVR DE, and SVR ME) were screened for their in vitro antioxidant, anti-Alzheimer, and antidiabetic enzymes inhibition activities. The antioxidant properties of Salvia extracts were determined using DPPH radical scavenging, ABTS radical scavenging, Alkaline DMSO superoxide radical scavenging, β-carotene bleaching, reducing power, and metal chelating activity assays. All extracts showed high antioxidant capacity and the antioxidant properties with the best performance were detected in the SAE ME and SVR ME. The extracts of S. aegyptiaca and S. verbenaca showed a low inhibitory activity of acetylcholinesterase (AChE), whereas, the methanol extract of S. aegyptiaca had the highest inhibitory activity on butyrylcholinesterase (BChE) (71.60 ± 4.33% for 100 µg/ml) compared to the other extracts. In vitro inhibitory effect on diabetic enzymes showed that the ME inhibited α-amylase enzyme with an IC50 86 and 101 µg/ml for SAE and SVR, respectively. Similarly, both extracts inhibited α-glucosidase with (IC50 97 and 150 µg/ ml, respectively). The decoction extracts exhibited lower activity on both enzymes

Effects of drying process on total phenolics, antioxidant activity and flavonoid contents of common Mediterranean herbs

Preprint

Full-text available

Apr 2015

Effects of drying process on total phenolics, antioxidant activity and flavonoid contents of common Mediterranean herbs

Article

Full-text available

Apr 2015

Total phenolic content and antioxidant capacity of hydromethanolic extracts of in vitro and ex vitro plantlets of Drosera spp

Article

Full-text available

Jun 2020

Drosera, is one of the most numerous genera of carnivorous plants. It has been reported to have pharmacological activities such as anticancer, antibacterial and anti-inflammatory. However, total phenolic content and antioxidant capacity have been poorly studied. Five specimens were in vitro propagated (D. binata, D. capensis Alba, D. capensis All Red, D. spatulata and D. spatulata x nidiformis) and acclimatized for three months. Total phenolic content (TPC) was quantified by the Folin-Ciocalteu test and the antioxidant capacity of the hydromethanolic extracts against the free radical 2,2-Diphenyl-1-picrylhydrazyl (DPPH) was determined. In vitro plantlets of D. capensis All Red showed the highest TPC (3.32 0.07 mg GAE/g) determined in dry weight. While, the highest antioxidant capacity determined in fresh weight, was obtained in D. capensis All Red and D. spatulata with 692.36 66.91 and 665.14 41.82 TE/g, respectively. The acclimatized plantlets of D. spatulata x nidiformis showed the highest TPC and the highest antioxidant capacity (both evaluated in fresh weight), with 6.13 0.07 mg GAE/g and 1027.91 4.56 TE/g, respectively. The specimen and the origin of the extracts influence the response of total phenolic content and antioxidant capacity.

Determination of drying kinetics, some physical, and antioxidant properties of papaya seeds undergoing microwave vacuum drying

Article

Full-text available

Oct 2019
J FOOD PROCESS ENG

The effects of microwave power (MP, 100–600 W) on the drying kinetics, as well as the physical and antioxidant properties of papaya seeds dried under microwave vacuum drying (MVD) were investigated. The results found that moisture diffusivity increased in the order of 10⁻⁸ with an increase in MP. Shrinkage increased from 1.2 to 4.9% and bulk density decreased from 3,441 to 1,091 kg/m³, respectively, while the moisture content decreased. The antioxidant contents of all of the MVD samples were higher than those of the samples dried under ambient air ventilation. An increase in MP decreased the total phenolic content from 14.69 to 10.66 mg gallic acid equivalent per gram dry weight (DW), increased both the β‐carotene and the total flavonoid content in the ranges of 0.2–0.35 mg β‐carotene equivalent per gram DW and 20.71 to 23.51 mg catechin equivalent per gram DW, respectively. Higher values of antioxidant activity were obtained at higher MP. The results have shown that the use of novel MVD technique in appropriate conditions can improve the overall drying efficiency and enhance the total yield of antioxidant content. Practical Applications Papaya seeds have great potential for use as a source of antioxidants. However, the best novel techniques for retaining high values of antioxidant compounds, and therefore recouping value from the wasted seeds, has not been widely reported on. This study has found that combined microwave vacuum drying (MVD) is a very beneficial drying method for the preservation of antioxidant content. A better antioxidant yield from dried papaya seeds was obtained using MVD at a higher MP of 600 W. Trolox equivalent antioxidant capacity of seeds dried using MVD was 27.62% higher than the samples dried using ambient air ventilation.

Ethanol Extraction of Active Ingredients and Antioxidants from Germinated Sangyod Rice

Article

Mar 2019

Dehydration of red bell-pepper ( Capsicum annuum L.): Change in drying behavior, colour and antioxidant content

Article

Oct 2011
FOOD BIOPROD PROCESS

The sun, oven (50 and 70°C) and microwave oven (210 and 700W) drying behaviors of red bell-pepper slices were investigated. Effects of these drying methods in terms of colour indices and antioxidant activity of pepper slices were also studied. “Midilli and Küçük” model exhibited high coefficient of determination (R2) values for all the drying methods used in the assay, ranging between 0.994–0.999, while “Page” and “Modified Page” models fit better for oven drying at 70°C. The calculated effective diffusivity (Deff) values (m2/s) of pepper slices for the drying processes ranged between 0.31 and 87.39×10−9. Sun dried and followed by microwave oven (700W) dried samples revealed the highest L*, a* and b* colour values than the other dried samples. Microwave oven dried (210W) and oven dried (50°C) samples exhibited the lowest TEAC and DPPH radical scavenging activities among the dried samples.

The Impact of Drying Methods on Quality Parameters of Purple Basil Leaves

Article

May 2021

Purple basil leaves dried with natural drying, which was the traditional method, convective drying at 50°C, which was the most common method, and microwave drying at 200, 600, and 1000 W, which were low, medium, and high powers. The drying processes lasted 4320, 195, 48, 25, and 14 minutes for natural, 50°C, 200, 600, and 1000 W, respectively. The most convenient color parameters and chlorophyll concentration to the fresh product were obtained at natural drying. While all drying methods were very close to fresh products regarding protein content; natural drying, 50°C, and 1000 W were found to had the highest concentration regarding P and K. Contrarily, 200 and 600 W were suitable for Ca and Mg conservation. The drying methods in which Na, Fe, Cu, Mn, and Zn reached the maximum were natural, 1000 W, 600 W, 200 W, and 50°C, respectively.

Antioxidative Activities of Aqueous and Ethanolic Extracts of Licorice Roots

Article

May 2014
Pakistan J Nutr

Suhayla K. Mohammed

The licorice roots, is known as a healthy nutrient for more than 3000 years. The antioxidant activities of licorice roots, aqueous and ethanolic extracts, have been studied by using two different methods (reducing power and chelating ability). It was found that the total phenolic compounds in aqueous and ethanolic extracts of licorice roots were 4.8 and 9.2 mg/100 mg dry extract, respectively. The flavonoids (which are a part of the phenolic compounds) were found to be 2.3 and 6.8 mg/100 mg dry extract in aqueous and ethanolic extract of licorice roots respectively. The ethanolic extract shows high antioxidative activity as compared with aqueous extract. The aqueous and ethanolic extracts of licorice roots show high reducing power ability comparing with their abilities as chelating agents. Thus, this study suggests that licorice extract can be used as a potential source of natural antioxidants.

Effect of Drying Methods on Total Antioxidant Capacity of Bitter Gourd (Momordica charantia) Fruit

Conference Paper

Full-text available

Nov 2013

The effect of thermal and non-thermal drying methods on hydrophilic and lipophilic antioxidant capacities of bitter gourd fruit was investigated in this study. The bitter gourd fruits were dried by following methods: (i) oven drying 40 degrees C, (ii) oven drying 50 degrees C, (iii) oven drying 60 degrees C, (iv) microwave drying (medium low power), (v) microwave drying (medium power) and (vi) freeze drying. Pure acetone and hexane were used to extract the hydrophilic and lipophilic antioxidant compounds from dried bitter gourd fruits. Freeze dried extracts reported to have highest values in DPPH scavenging activity (hydrophilic and lipophilic fractions), FRAP (lipophilic fraction) and TPC (hydrophilic and lipophilic fraction). Thermal drying slightly increased the values of DPPH scavenging activity, FRAP and TPC assays for hydrophilic extracts. Results concluded bitter gourd fruit is a good source of natural antioxidants and its total antioxidant quality was most preserved by freeze drying. Additionally, the higher value reported in DPPH scavenging activity, FRAP and TPC assays for lipophilic extracts than the hydrophilic extracts suggested that the lipophilic antioxidant compounds of bitter gourd fruit might possess stronger antioxidant power than its counterpart.

Effect of gamma and microwave irradiation on antioxidant and antimicrobial activities of Cinnamomum zeylanicum and Echinacea purpurea

Article

Jan 2014

The effect of gamma and microwave irradiation on antioxidant and antimicrobial activities of Cinnamomum zeylanicum and Echinacea purpurea were investigated. In this study, all samples were exposed to gamma irradiation at doses 10, 15, 20 and 25 kGy and microwave irradiation at power of 100, 180 and 300 W for 5 min. In order to undergo the sequence expriments, the hydroalcoholic (EtOH 50%) extracts of two medicinal plants were prepared. The antioxidant activity of irradiated and control samples were evaluated by DPPH radical scavenging (RS), ferric reducing power (FRP), β-carotene bleaching (BCB) and total phenolic content (TPC) of sampels. In order to study the antimicrobial activity, for determination of minimal inhibitory concentration (MIC) on E. coli and S. aureus, broth diluting method was used. Regarding gamma irradiation, no significant effect on antioxidant and antimicrobial activities of Cinnamon was observed. However, at doses higher than 10 kGy, higher radical scavenging activity (RSA) of was observed for Cinnamon extract (by DPPH method). By increasing the irradiation dose, FRP and TPC of samples increased and no adverse effect was observed on antimicrobial activity of Echinacea extract. Microwave treatments of Cinnamon, had no significant effect on antioxidant and antimicrobial activities of its extract. However, at 300 W an increase in antioxidative and antimicrobial activities of Echinacea extract was observed.

Effect of microwave blanching on antioxidant activity, phenolic compounds and browning behaviour of some fruit peelings

Article

Aug 2019
FOOD CHEM

Fruit peelings are increasingly being used as ingredients for the formulation of functional foods. In this study, the antioxidant activity and browning behaviour of free and bound phenolic fractions of mango, apple, orange and banana peelings microwave-blanched at 720 W for 1, 3 and 5 min were determined. The fractions were equally analyzed for their phenolic content and composition. Generally, increased microwave blanching was accompanied by a significant increase of total phenolics content in free and bound fractions. Increased antioxidant activities at 3 and 5 min of blanching varied with the type of fruit peelings. Browning rates decreased with microwave blanching time except in the case of apple peelings. Epicatechin, ferulic acid, caffeic acid, rosmarinic acid, p-coumaric acid and gallic acid were identified in fruit peelings. Generally, microwave blanching for 3 or 5 min was found to preserve antioxidant activities and reduce the browning rate.

Drying Kinetics and Changes of Total Phenolic Content, Antioxidant Activity and Color Parameters of Mango and Avocado Pulp in Refractance Window Drying

Article

Jan 2022

Refractance window drying is an innovative technology belonging to the fourth generation of drying technologies that could enhance the quality of the dried product and improve the drying process. In this study, two factors with the type of fruit pulps (avocado and mango) and drying temperature (ranging from 80 to 95°C) were investigated. Results showed that in refractance window drying, the evaporation process rapidly occurred, mainly in the falling-rate period with undetectable the constant-rate period. The Weibull was the best fit model among eight investigated mathematical models that could determine the drying behavior. The effective diffusivity was found to be from 4.25x10 -10 m 2 /s to 7.24x10 -10 m 2 /s for avocado pulp, and from 4.50x10 -10 m 2 /s to 10.67x10 -10 m 2 /s for mango pulp when the drying temperature was changed from 80 to 95°C. Moreover, the corresponding activation energy was 32.06 and 66.03 kJ/mol for avocado and mango pulp moisture evaporation, respectively, and the highest quality of powders of both dried pulps was obtained after processing at 90°C. The refractance window drying revealed a high potential in the production of fruit powders from avocado and mango due to the high retention of more than 80% of total phenolic content (TPC) and antioxidant activity. TPC could be used as a useful criterion for the evaluation of the drying process in terms of dried product quality.

Phenolic compounds and antioxidant activity are differentially affected by drying processes in celery, coriander and parsley leaves

Article

Mar 2022

Convective drying (CO) is the most common technique for drying herbs, although it may diminish phenolic compounds content. Microwave drying (MW) has been suggested as an alternative, although its effects on phenolic compounds remain to be explored. The aim of this study is to compare the effects of different convective temperatures (40, 80 and 120 °C) and microwave powers (100, 500 and 1000 W) on drying time, polyphenols classes (HPLC‐DAD) and antioxidant capacity in celery, coriander and parsley leaves. Microwave procedure reduced drying time (MW: 3 h–7 min; CO: 25–1.5 h) resulting more effective than CO. Increasing temperatures led to an initial decrease in total phenolic content (TPC) and antioxidant activity followed by an increase, potentially by the release of bound phenolic acids. Regarding MW, the highest polyphenol content was generally observed at 500 W, probably due to the hydroxycinnamic acid's rise. Antioxidant capacity was similar at 500 and 1000 W. There was a good agreement between TPC and antioxidant capacity. Consequently, MW seems a good alternative to reduce drying time. However, the maintenance or improvement of phenolic activity depends on the food matrix. Indeed, the best drying system and conditions to preserve phenolic compounds were variable depending on the herb type: celery (CO at 40 °C), coriander (both CO at 40 °C and MW at 500 W) and parsley (MW at 100 W). Effect of drying process type on polyphenols content and activity in three culinary herbs.

Protein Content and Antioxidant Activity of Distillers’ Spent Grain Dried at 150°C with Superheated Steam and Hot Air

Article

Sep 2012

The quality of dried distillers’ grain (DDG) is of great importance, and due to concerns regarding drying efficiency, various drying methods have been proposed. The objective of this study was to evaluate the protein content and antioxidant activity of DDG using two different drying media: (1) hot air at 150°C and (2) and superheated steam (SS) at 150°C. The results were compared to a reference sample dried at near ambient air temperature of 30°C. Protein content ranged from 15.1 to 16.4% wb for all samples. With respect to phenolic content, ethanolic extraction (3.1–12.9 mg GAE/g) was more effective than aqueous extraction (0.87–2.9 mg GAE/g). The DDG samples dried with SS had the highest phenolic contents among the analyzed samples (p

Antioxidant Activity and Total Phenolics in Selected Fruits, Vegetables, and Grain Products

Article

Full-text available

Oct 1998

The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. The total phenolic content, determined according to the Folinâˆ’Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the Î²-carotene bleaching method expressed as AOX (Î” log A470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products

Effect of Heat Treatment on the Antioxidant Activity of Extracts from Citrus Peels

Article

Full-text available

Jul 2004

The effect of heat treatment on the antioxidant activity of extracts from Citrus unshiu peels was evaluated. Citrus peels (CP) (5 g) were placed in Pyrex Petri dishes (8.0 cm diameter) and heat-treated at 50, 100, or 150 degrees C for 10, 20, 30, 40, 50, and 60 min in an electric muffle furnace. After heat treatment, 70% ethanol extract (EE) and water extract (WE) (0.1 g/10 mL) of CP were prepared, and total phenol contents (TPC), radical scavenging activity (RSA), and reducing power of the extracts were determined. The antioxidant activities of CP extracts increased as heating temperature increased. For example, heat treatment of CP at 150 degrees C for 60 min increased the TPC, RSA, and reducing power of EE from 71.8 to 171.0 microM, from 29.64 to 64.25%, and from 0.45 to 0.82, respectively, compared to non-heat-treated control. In the case of WE from CP heat-treated at the same conditions (150 degrees C for 60 min), the TPC, RSA, and reducing power also increased from 84.4 to 204.9 microM, from 15.81 to 58.26%, and from 0.27 to 0.96, respectively. Several low molecular weight phenolic compounds such as 2,3-diacetyl-1-phenylnaphthalene, ferulic acid, p-hydroxybenzaldoxime, 5-hydroxyvaleric acid, 2,3-diacetyl-1-phenylnaphthalene, and vanillic acid were newly formed in the CP heated at 150 degrees C for 30 min. These results indicated that the antioxidant activity of CP extracts was significantly affected by heating temperature and duration of treatment on CP and that the heating process can be used as a tool for increasing the antioxidant activity of CP.

Bioavailability of Phenolic Compounds

Article

Full-text available

Feb 2004

Sibel Karakaya

Phenolic compounds in foods originate from one of the main classes of secondary metabolites in plants. They are essential for the growth and reproduction of plants, and are produced as a response for defending injured plants against pathogens. In recent years, there is a growing interest in phenolic compounds and their presumed role in the prevention of various degenerative diseases, such as cancer and cardiovascular diseases. The importance of antioxidant activities of phenolic compounds and their possible usage in processed foods as a natural antioxidant have reached a new high in recent years. The absorption and bioavailability of phenolics in humans are also controversial. Data on these aspects of phenolics are scarce and merely highlight the need for extensive investigations of the handling of phenolics by the gastrointestinal tract and their subsequent absorption and metabolism. In this article, absorption, metabolism, and the bioavailability of pheniolic compounds are reviewed.

Quantitative evaluation of the antioxidant properties of garlic and shallot preparations

Article

Apr 2006
NUTRITION

Shallots and garlic are an important part of the diet of many populations and there is long-held belief in their health enhancing properties. This study tested whether fresh and commercial shallot and garlic preparations have antioxidant properties that might justify such claims. Samples produced by pressing and extraction of bulbs were tested for their ability to decrease free radicals of 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and the results were compared with commercial preparations of aged garlic and with trolox, butylated hydroxytoluene, N-acetyl cysteine, and gallic acid. We also measured the phenolic content of the extracts and the amounts of diallyl sulfides present. Antioxidant activities were directly related to the contents of phenolic compounds, with the fresh freeze-dried extracts significantly more potent than commercial preparations. Hexane-extracted shallot and garlic had the highest antioxidant activity, followed by water extracts, bulb pressings, and commercial products. Fresh shallot and garlic preparations inhibited lipid oxidation and accelerated their decomposition but had no effect on protein oxidation. Organic solvent and aqueous extracts of garlic and shallot bulbs had significant antioxidant potential, as measured by decreases in free radicals and an ability to inhibit lipid oxidation.

Erratum to: “Advances in dehydration of foods”

Article

Jan 2001

Microwave/air and microwave finish drying of banana

Article

May 2000
J FOOD ENG

Medeni Maskan

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.

Antioxidant in fruits and vegetables — The millennium's health

Article

Jul 2008
INT J FOOD SCI TECH

Some of the most exciting research in the last decade has been the discovery of a group of nutrients, which have protective effects against cell oxidation. These naturally occurring compounds impart bright colour to fruits and vegetables and act as antioxidants in the body by scavenging harmful free radicals, which are implicated in most degenerative diseases. Epidemiological studies have established a positive correlation between the intake of fruits and vegetables and prevention of diseases like atheroscelerosis, cancer, diabetes, arthritis and also ageing. So pronounced has been their effect on ageing that they have been called ‘fountains of youth’. Fruits and vegetables have thus had conferred on them the status of ‘functional foods’, capable of promoting good health and preventing or alleviating diseases. Phenolic flavonoids, lycopene, carotenoids and glucosinolates are among the most thoroughly studied antioxidants. The present review highlights the potential of fruits and vegetables rich in antioxidants, their health benefits and the effect of processing on the bioavailability of these nutrients. The paper also reviews some of the important methods used to determine the antioxidant activity.

Microwave Drying Characteristics of Parsley

Article

Oct 2004

Yurtsever Soysal

Parsley (Petroslinum crispum Mill.) leaves were dried in a domestic microwave oven to determine the effects of microwave output power on drying time, drying rate and the dried product quality in terms of colour. Seven different microwave output powers ranging from 360 to 900 W were used in the drying experiments. Drying took place mainly in constant rate and falling rate periods. After a short heating period a relatively long constant rate period was observed. Approximately 40·5% of the water was removed in this period. The rapidly decreasing falling rate period followed the constant rate period. As the drying progressed, the loss of moisture in the product caused a decrease in the absorption of microwave power and resulted in a fall in the drying rate. Increasing the microwave output power resulted in a considerable decrease in drying time (probability P<0·01). The semi-empirical Page's equation used to describe the drying kinetics of dried leaf materials gave an excellent fit for all data points with values for the coefficient of determination R2 of greater than 0·997 and for the standard error of estimates (SEE) of lower than 0·0188. The value of the drying constant increased with increased microwave output power. No significant differences were observed between the colour parameters of fresh and microwave-dried leaf materials, except for some decrease in whiteness L value (P>0·05). The change in colour values was not dependent on the microwave output power. Although some darkening occurred, microwave drying maintained a good green colour close to that of the original fresh parsley leaves. By working at 900 W instead of 360 W, the drying time could be reduced by 64% with a good quality product.

The application of response surface methodology to the production of phenolic extracts of lemon grass, galangal, holy basil and rosemary

Article

Feb 2006
INT J FOOD SCI TECH

The effects of independent variables (ethanol:water ratio, temperature and time) on the extraction yield and antioxidant properties of phenolic extracts from lemon grass, galangal, holy basil and rosemary were studied. The extraction solvent ratio of ethanol to water was found to have a significant (P < 0.05) influence on extraction yield, reducing power and total phenolic content, but not on the antioxidant activity of all herb and spice samples, while extraction temperature had only minor effects. Extraction time had a significant (P < 0.05) effect only on the reducing power of holy basil extracts. The optimum extraction conditions, i.e. extraction solvent ratio of ethanol to water, extraction temperature and extraction time for maximum total phenolic content, were 3:1 at 25 °C for 30 min for lemon grass, 3:1 at 75 °C for 90 min for galangal and holy basil and 3:1 at 75 °C for 30 min for rosemary.

Antioxidant properties of Phyllanthus amarus extracts as affected by different drying methods

Article

Nov 2007
LWT-FOOD SCI TECHNOL

The total phenolic content (TPC) and antioxidant activity of fresh and dried Phyllanthus amarus plant materials were evaluated using the Folin-Ciocalteau method, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and ferric reducing antioxidant power (FRAP) assays. Different drying treatments led to significant reduction (P<0.05) in antioxidant properties of P. amarus methanolic extracts, with microwave drying causing the highest decrease in TPC and antioxidant activity exhibited by the reduction in both radical scavenging activity and FRAP. On the other hand, boiling water extracts appeared to exhibit significantly stronger antioxidant potentials (P<0.05) even in dried plant materials due to greater solubility of compounds, breakdown of cellular constituents as well as hydrolysis of tannins. Its strong free radical scavenging activity suggests that it has great potential in the food industry as functional food ingredient.

Effect of drying method on the sorption of model fruit powders

Article

Dec 1998
J FOOD ENG

Pectin-sugar gels were dehydrated with four different drying methods: freeze, microwave, vacuum and conventional drying to a moisture content of about 5%. The effect of the drying method on the water sorption properties of dehydrated products was evaluated at 25 °C. Freeze-dried gel adsorbed more water vapour than microwave-dried gel, which had a higher sorption capacity than vacuum- and conventional-dried product. The sorption isotherms were in agreement with the reported shape for high sugar foodstuffs. Three different equations proposed in the literature (GAB, Oswin, Hasley) were used to fit the sorption data. The GAB equation gave the best fit to the experimental data. The porosity of the dehydrated products depended on the drying method, ranging between 0.2 and 0.5. Freeze- and vacuum-dried pectin developed the highest porosity, whereas the lowest porosity was obtained using conventional and microwave drying. Hunter colour parameters (L, a, b) also depended on the drying method. The colour of freeze- and vacuum-dried pectin was close to that of commercial pectin, while the colour of the conventional- and microwave-dried product changed significantly.

Influence of processing on the antioxidant properties of fruit and vegetables

Article

Mar 1999
TRENDS FOOD SCI TECH

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.

Drying of carrots in microwave and halogen lamp-microwave combination ovens

Article

Aug 2005
LWT-FOOD SCI TECHNOL

Carrot slices were dried by using microwave, halogen lamp–microwave combination and hot-air drying. Microwave and halogen lamp–microwave combination drying were applied after carrots were dried to 0.47 kg moisture/kg dry solid by hot-air drying. Drying time, rehydration capacity and colour of the carrots dried by different methods were compared. The increase in microwave oven power level decreased the drying time. Microwave drying at the highest power and halogen lamp–microwave combination drying reduced the drying time to an extend of 98% in comparison to conventional hot-air drying and a high-quality dried product was obtained. Moreover, in the case of halogen lamp–microwave combination drying, moisture level was reduced to a level, which is lower than the one achieved by other methods. Less colour change occurred when microwave and halogen lamp–microwave combination drying were applied. Carrots dried in microwave and halogen lamp–microwave combination oven had lower L*, higher a* and b* values and had higher rehydration capacity as compared to hot-air drying.

Drying of garlic (Allium sativum) cloves by microwave-hot air combination

Article

Nov 2001
J FOOD ENG

Garlic cloves were dried with hot air and combined microwave–hot air drying methods in an experimental dryer. The combined microwave–hot air drying experiments were carried out with 100 g sample sizes at temperatures of 40°C, 50°C, 60°C and 70°C at air velocities of 1.0 and 2.0 m/s, using continuous microwave power of 40 W. For comparison of hot air drying, the same sample sizes were taken for experiments and the drying air temperatures and air velocity were 60°C and 70°C, and 2.0 m/s respectively. The total drying time, the color and flavor strength of dried garlic cloves were used to evaluate the performance of the combined microwave–hot air drying and the conventional hot air drying processes. Combined microwave–hot air drying resulted in a reduction in the drying time to an extent of 80–90% in comparison to conventional hot air drying and a superior quality final product.

Microwave and air drying I. Fundamental considerations and assumptions for the simplified thermal calculations of volumetric power absorption

Article

Jul 1997
J FOOD ENG

The thermal modelling of foods in a microwave field was investigated. The purpose of this work was to simplify the complex thermal modelling necessary for the drying calculations. The calorimetric technique was used to model the power absorbed with respect to sample size and oven loading. A linear relationship between power absorbed and sample diameter was obtained, while a non-linear behaviour was observed between the power absorbed by samples of various diameters and oven loading.

Effect of microwave power, air velocity and temperature on the final drying of osmotically dehydrated bananas

Article

Jul 2007
J FOOD ENG

This paper reports on a study of the final stage of microwave-hot air drying of osmotically dehydrated bananas, focusing on the effects of microwave power, air temperature and air velocity on drying kinetics and product quality, evaluated in terms of colour, apparent volume and porosity. The drying process was divided into three periods: phase I (760 W; 2 kgmoisture/kgdry matter); phase II (380 W; 0.67 kgmoisture/kgdry matter); and phase III (0 W, 76 W, 150 W or 230 W up to the final sample moisture of 0.17 kgwater/kgd m). Three conditions for the hot air were tested: 50 °C and 3.3 m/s; 70 °C and 3.3 m/s; 70 °C and 5.7 m/s. The results show that increasing the microwave power in phase III increased the drying rate, thus making the drying time shorter. However, higher microwave power also caused temperature runaway leading to charring on the dried product. Air flow cools the product surface and improves product quality by reducing charring.

Trends in microwave-relate drying of fruits and vegetables

Article

Oct 2006
TRENDS FOOD SCI TECH

Microwave (MW)-related (MW-assisted or MW-enhanced) combination drying is a rapid dehydration technique that can be applied to specific foods, particularly to fruits and vegetables. Increasing concerns over product quality and production costs have motivated the researchers to investigate and the industry to adopt combination drying technologies. The advantages of MW-related combination drying include the following: shorter drying time, improved product quality, and flexibility in producing a wide variety of dried products. But current applications are limited to small categories of fruits and vegetables due to high start-up costs and relatively complicated technology as compared to conventional convection drying. MW-related combination drying takes advantages of conventional drying methods and microwave heating, leading to better processes than MW drying alone. This paper presents a comprehensive review of recent progresses in MW-related combined drying research and recommendations for future research to bridge the gap between laboratory research and industrial applications.

Chemical composition, physical properties, and antioxidant activities of yam flours as affected by different drying methods

Article

Oct 2003
FOOD CHEM

Yams (the tubers of the Dioscorea spp.), consumed and regarded as medicinal food in traditional Chinese herbal medicine, are seasonal foods and easily deteriorate during storage. It is of great importance to prolong the storage of yams for supplying in the off-season and without losing nutritional functionality. Three varieties of yams, Dioscorea alata (cultivars of Tai-Nung no. 2 and Ta-Shan) and D. purpurea (cultivar of Ming-Chien), were made into flours by freeze-drying, hot air-drying, and drum-drying in this report. The proximate compositions and physical properties, as well as antioxidant activities, of yam flours were determined. While drying methods showed significant effects on the moisture contents of yam flours, they had no marked effects on other components of yam flours. Colour attributes and physical properties were all affected by drying methods to different extents. While freeze-drying usually preserved more antioxidant activity of the yam flours, yam flours made of different yam varieties showed different antioxidant mechanisms.

Effect of far-infrared radiation on the antioxidant activity of water extracts from peanut hulls

Article

Mar 2006
FOOD CHEM

The antioxidant activities of peanut (Arachis hypogaea L.) hull extracts were evaluated after far-infrared (FIR) radiation or heat treatment. Peanut hulls in petri dishes were FIR-irradiated or heat-treated (150 °C) for 5, 10, 15, 20, 40 or 60 min. The water extracts (300 mg/10 mL) of peanut hulls (WEPH) were prepared and their total phenol contents (TPC), radical scavenging activity (RSA), and reducing power were determined. The antioxidant activities of WEPH increased as the time of heating or FIR-radiation increased. When peanut hulls were FIR-irradiated at 150 °C for 60 min, the values of TPC, RSA, and reducing power of WEPH increased from 72.9 to 141.6 μM, 2.34% to 48.83%, and 0.473 to 0.910, respectively, compared to the untreated controls. Heat treatment of peanut hull under the same conditions (150 °C for 60 min) also increased the TPC, RSA, and reducing power of WEPH from 72.9 to 90.3 μM, 1.90% to 23.69%, and from 0.471 to 0.718, respectively. The result indicated that FIR-radiation or heat treatment on peanut hulls increased the antioxidant activities of WEPH.

Antioxidant activities of aqueous extracts of selected plants

Article

Dec 2006
FOOD CHEM

The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxidant capacity (TEAC), were studied using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical) scavenging and reducing ferric ion antioxidant potential (FRAP) assays. Their cupric ion chelating activities (CCA) and total polyphenol contents (TPC) were also determined. A strong correlation between TEAC values obtained for the DPPH assay (TEACDPPH) and those for the FRAP assay (TEACFRAP) implied that compounds in the extracts were capable of scavenging the DPPH free radical and reducing ferric ions. A satisfactory correlation of TPC with TEACDPPH and TEACFRAP suggested that polyphenols in the extracts were partly responsible for the antioxidant activities while its correlation with CCA was poor, indicating that polyphenols might not be the main cupric ion chelators. Principal component analysis (PCA) indicated that TEACDPPH, TEACFRAP and TPC contributed to the total variation in the antioxidant activities of the plants.

The Effect of Microwave Heating of Fresh Orange Peels on the Fruit Tissue and Quality of Extracted Pectin

Article

Jun 2004
CARBOHYD POLYM

The effect of microwave pretreatment of fruit raw material on some physical properties of the orange tissue was investigated. Scanning electron micrographs showed that microwave heating led to destruction of the parenchymal cells. It was also found that specific surface and the water absorption capacity of the orange tissue, and the endogenous enzymes of the peels were inactivated. As a result of this pectin extraction was facilitated. Considerable increasing in pectin yield and was attained (190% from oranges from crop of 1996 and over 250% for oranges of crop 1997 as compared with control). The quality of the pectin was also improved.

Advances in dehydration of food

Article

Sep 2001
J FOOD ENG

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.

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Article

Dec 2007
FOOD CHEM

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.

A Fraction Conversion Kinetic Model for Thermal Degradation of Color in Red Chilli Puree and Paste

Article

Sep 2002
LWT-FOOD SCI TECHNOL

The kinetics of degradation of color was evaluated using a fraction conversion model during thermal treatment of red chilli puree at 60, 70, 80 and 90°C (up to 20 min) and storage of red chilli paste at 5, 25 and 37°C (up to 6 mo). Red chilli puree was subjected to heat treatment at different temperatures in a well-stirred water bath. Test samples were removed from the bath at selected time intervals (0–20 min after come-up), cooled immediately and analysed for color using a Hunterlab colorimeter. Chilli paste was prepared by a standard formulation by adding common salt (8%) and the required volume of citric acid to bring the pH to 4.0. The paste was thermally processed at 85°C for 15 min, filled into glass bottles and stored at selected temperatures for 6 mo. Red chilli color was expressed as a tristimulus combination value (L·a·b) as well as the total color difference (ΔE). The fraction conversion model adequately described the kinetic changes in both color values during thermal treatment of puree and storage of puree. The process activation energies were 24.2 and 24.8 kJ/mol, respectively, for ΔE and L·a·b during the thermal treatment, and during the storage the respective values were 24.1 and 25.0 18;kJ/mol. Up to the end of the 6-mo storage, the paste was microbiologically stable with no major changes in other physico-chemical characteristics.

Approaches to improving the quality of dried fruit and vegetables

Article

Microwave and hot-air drying of Thai red curry paste

Article

Nov 2008
MAEJO INT J SCI TECH

Inchuen Sudathip

Thai red curry paste was dried with two different drying methods: microwave and hot-air drying. The microwave drying was carried out in a microwave oven with output power of 180, 360 and 540 W, while the hot-air drying was carried out at drying air temperatures of 60, 70 and 80 C. The drying time of microwave drying process to reduce the moisture content of red curry paste from 2.58 to 0.08 g water/g dry matter was much shorter than that of the hot-air drying process. An increase in the microwave power significantly decreased the drying time. In the hot-air drying, increasing the drying air temperature also significantly decreased the drying time. Microwave drying process of red curry paste consisted of three drying periods, i.e. heating up, constant rate and falling rate periods, while hot-air drying process consisted of two drying periods, i.e. heating up and falling rate periods. To describe the effect of microwave power and drying air temperature on drying kinetics of red curry paste, three different mathematical thin-layer equations, i.e. Lewis, Page and Henderson-Pabis models, were used to fit the drying data. The fitness by these models was evaluated using the coefficient of determination (R2), the reduced chi-square (2) and the root mean square error (RMSE). The Page model provided the best fit to both microwave and hot-air drying experimental data.

Antioxidant Activity and Phenolic Compounds in Selected Herbs

Article

Nov 2001

The antioxidant capacities (oxygen radical absorbance capacity, ORAC) and total phenolic contents in extracts of 27 culinary herbs and 12 medicinal herbs were determined. The ORAC values and total phenolic contents for the medicinal herbs ranged from 1.88 to 22.30 micromol of Trolox equivalents (TE)/g of fresh weight and 0.23 to 2.85 mg of gallic acid equivalents (GAE)/g of fresh weight, respectively. Origanum x majoricum, O. vulgare ssp. hirtum, and Poliomintha longiflora have higher ORAC and phenolic contents as compared to other culinary herbs. The ORAC values and total phenolic content for the culinary herbs ranged from 2.35 to 92.18 micromol of TE/g of fresh weight and 0.26 to 17.51 mg of GAE/g of fresh weight, respectively. These also were much higher than values found in the medicinal herbs. The medicinal herbs with the highest ORAC values were Catharanthus roseus, Thymus vulgaris, Hypericum perforatum, and Artemisia annua. A linear relationship existed between ORAC values and total phenolic contents of the medicinal herbs (R = 0.919) and culinary herbs (R = 0.986). High-performance liquid chromatography (HPLC) coupled with diode-array detection was used to identify and quantify the phenolic compounds in selected herbs. Among the identified phenolic compounds, rosmarinic acid was the predominant phenolic compound in Salvia officinalis, Thymus vulgaris, Origanum x majoricum, and P. longiflora, whereas quercetin-3-O-rhamnosyl-(1 --> 2)-rhamnosyl-(1 --> 6)-glucoside and kaempferol-3-O-rhamnosyl-(1 --> 2)-rhamnosyl-(1 --> 6)-glucoside were predominant phenolic compounds in Ginkgo biloba leaves.

Antioxidant Activity of the Main Phenolic Compounds Isolated from Hot Pepper Fruit ( Capsicum annuum L.)

Article

Apr 2005

Four cultivars (Bronowicka Ostra, Cyklon, Tornado, and Tajfun) of pepper fruit Capsicum annuum L. were studied for phenolics contents and antioxidant activity. Two fractions of phenolics, flavonoids (with phenolic acids) and capsaicinoids, were isolated from the pericarp of pepper fruit at two growth stages (green and red) and were studied for their antioxidant capacity. Both fractions from red fruits had higher activities than those from green fruits. A comparison of the capsaicinoid fraction with the flavonoid and phenolic acid fraction from red fruit with respect to their antioxidant activity gave similar results. Phenolic compounds were separated and quantified by LC and HPLC. Contents of nine compounds were determined in the flavonoid and phenolic acid fraction: trans-p-feruloyl-beta-d-glucopyranoside, trans-p-sinapoyl-beta-d-glucopyranoside, quercetin 3-O-alpha-l-rhamnopyranoside-7-O-beta-d-glucopyranoside, trans-p-ferulyl alcohol-4-O-[6-(2-methyl-3-hydroxypropionyl] glucopyranoside, luteolin 6-C-beta-d-glucopyranoside-8-C-alpha-l-arabinopyranoside, apigenin 6-C-beta-d-glucopyranoside-8-C-alpha-l-arabinopyranoside, lutoeolin 7-O-[2-(beta-d-apiofuranosyl)-beta-d-glucopyranoside], quercetin 3-O-alpha-l-rhamnopyranoside, and luteolin 7-O-[2-(beta-d-apiofuranosyl)-4-(beta-d-glucopyranosyl)-6-malonyl]-beta-d-glucopyranoside. The main compounds of this fraction isolated from red pepper were sinapoyl and feruloyl glycosides, and the main compound from green pepper was quercetin-3-O-l-rhamnoside. Capsaicin and dihydrocapsaicin were the main components of the capsaicinoid fraction. A high correlation was found between the content of these compounds and the antioxidant activity of both fractions. Their antioxidant activities were elucidated by heat-induced oxidation in the beta-carotene-linoleic acid system and the antiradical activity by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) decoloration test. The highest antioxidant activity in the beta-carotene-linoleic acid system was found for trans-p-sinapoyl-beta-d-glucopyranoside, which was lower than the activity of free sinapic acid. Quercetin 3-O-alpha-l-rhamnopyranoside had the highest antiradical activity in the DPPH system, which was comparable to the activity of quercetin. The activities of capsaicin and dihydrocapsaicin were similar to that of trans-p-feruloyl-beta-d-glucopyranoside in the DPPH model system.

Effect of method drying on sorption characteristics of model fruit powders

Jan 1999
J FOOD ENG
381-392

E Tsami
M K Krokida
A E Drouzas

Tsami, E., M.K. Krokida and A.E. Drouzas. 1999. Effect of method drying on sorption characteristics of model fruit powders. J. Food Eng. 38: 381-392.

Effect of Drying Methods on Chemical Composition, Color and Antioxidant Properties of Thai Red Curry Powder

Abstract

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