The effect of seven drying treatments (sun, shade, oven 60 °C, oven 80 °C, oven 100 °C, microwave and freeze-drying) were evaluated with respect total flavonoid (TFC), phenolic (TPC), antioxidant activity, vitamin C and color characteristics of green tea. In general, drying increased antioxidant activity, TPC, TFC and chlorophyll content, while it led to a decrease in vitamin C. The highest TPC (209.17 mg Gallic acid/gdw) and TFC (38.18 mg Quercitin/gdw) were obtained in oven drying at 60 and 100 °C, respectively. Among methods, oven drying at 60 °C revealed the highest radical scavenging activity (IC50 = 167.166 μg/ml), while microwave showed the lowest one (IC50 = 505.5 μg/ml). Similar trend was also observed in reducing power assay. The highest vitamin C (16.36 mg/100gDM) and Chlorophyll a (17.35 mg/l) were obtained in freeze drying. Finally, sun and freeze drying methods were considered as the least and the most desirable drying methods, respectively the final color of green tea leaves.

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Evaluation of seven different drying treatments in respect to total flavonoid, phenolic, vitamin C content, chlorophyll, antioxidant activity and color of green tea ( Camellia sinensis or C. assamica ) leaves

This study evaluated freeze drying combined with microwave vacuum drying (FD-MVD) for functional okra snacks. FD-MVD was compared using four different drying methods: hot air drying (AD), freeze drying (FD), microwave vacuum drying (MVD), and hot air drying combined with microwave vacuum drying (AD-MVD). For main antioxidant components including epigallocatechin gallate (EGC), epicatechin gallate (EGCG), epigallocatechin (ECG), quercetin 3-O-diglucoside, and quercetin 3-O-(malonyl) and antioxidant properties (IC50, AEAC, FRAP, ABTS, TF, and TPC) and color (L*, a*, and b*), the values of FD-MVD were similar to those of FD and significantly higher than those of AD, MVD, and AD-MVD (P

Evaluation of freeze drying combined with microwave vacuum drying for functional okra snacks: Antioxidant properties, sensory quality, and energy consumption

Summary
The aim of this study was to investigate the effect of freeze-drying, hot air-drying and vacuum-drying at 70, 90 and 110 °C, on dried lemon pomace polyphenols and antioxidant capacity. The total phenolic content and antioxidant capacity were higher in lemon pomace dried by hot air or under vacuum than those dried by freeze-drying and increased as the temperature increased. The highest total flavonoid content was recorded in the pomace dried under vacuum at 70 and 90 °C. Lemon pomace dried by freeze-drying had the highest neohesperidin content, whereas pomace dried under vacuum at 70 °C had the highest rutin and p-coumaric acid content. The highest gallic acid content was recorded in the pomace dried by hot air at 110 °C. The results of this study indicate that drying technique should be carefully selected according to the bioactive compounds aimed to be extracted.

/pdf/effect-of-vacuum-drying-hot-air-drying-and-freeze-drying-on-3mrg67tmi7.pdf

Effect of vacuum‐drying, hot air‐drying and freeze‐drying on polyphenols and antioxidant capacity of lemon (Citrus limon) pomace aqueous extracts

Combination of argan oil and phospholipids for the development of an effective liposome-like formulation able to improve skin hydration and allantoin dermal delivery

Phenolic content, antioxidant activity and effective compounds of kumquat extracted by different solvents.

Quantitative analysis of allantoin and allantoic acid in yam tuber, mucilage, skin and bulbil of the Dioscorea species

Drying effect on flavonoid composition and antioxidant activity of immature kumquat.

Summary

The purpose of this study was to investigate the enhancing effect of heat treatment (110 and 130 °C for 0.5, 1.0, 1.5 and 2.0 h, and 150 °C for 1.5 h) on antioxidant activity and phenolic compounds of immature calamondin (Citrus mitis Blanco). The results indicated that heat treatment could enhance the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging potency, oxygen radical absorbance capacity (ORAC) and total phenolic content. However, the major flavonoid, 3′,5′-di-C-β-glucopyranosylphloretin (DGPP), decreased drastically after being heated at ≥130 °C over 1.5 h. The increasing ratio of absorbance at UV420 nm coincided with the change of the antioxidant activity. Therefore, it was concluded that the browning products resulted in the increase of the antioxidant activity of immature calamondin heated at ≥130 °C over 1.5 h, while the increase of antioxidant activity at 110 and 130 °C ≤ 1.0 h heating was due to increased phenolic content.

Lin-Huei A. Ferng

Papers

Quantitative analysis of allantoin and allantoic acid in yam tuber, mucilage, skin and bulbil of the Dioscorea species

Drying effect on flavonoid composition and antioxidant activity of immature kumquat.

Enhancing the antioxidant activity of immature calamondin by heat treatment