Studying the effect of different drying methods on phenolic content, antioxidant activity, color and antimicrobial activity in Assam tea (Camellia assamica)

The present study was conducted to determine the effect of freeze drying (FD), vacuum drying (VD), sun drying (SD) and hot air oven/tray drying (HD) drying on antioxidant activity, antimicrobial activity and color of Camellia assamica (two samples) collected from Kokrajhar area, Assam. The objective of this study is to observe effect of different drying methods on antioxidant, antimicrobial activity and color of Camellia assamica. In the experiment, to determine the antioxidant activity DPPH assay was used. Color of the tea samples are measured with Haunter Lab colorimeter and antimicrobial activity is done by disc diffusion method against Escherichia coli. Experimental evidence has shown that freeze drying exhibit rich source of polyphenol content and flavoind content than the vacuum drying, normal drying and hot air oven drying present in tea. The maximum TPC calculated was 194.5 ± 9.72, TFC of 58.7 ± 2.93 (mg of QAE/gm tea extract), with an antioxidant activity of 87.22% amongst both the samples at − 40 °C, 72 h in FD. The color analysis for the FD sample was found to be lighter than other drying method at − 40 °C, 72 h with ΔL* = 41.3 CIE units, ΔE = 47.8 CIE units, ΔC = 25.6 CIE units and ΔH = 70.06° and analytically chlorophyll was found to be Ch-a = 2.23 (mg/gm), Ch-b = 1.88 (mg/gm), in comparison of both the samples. The maximum inhibition zone was formed of 4.3 cm for FD and against 3 cm for VD sample.