Research on microwave‐assisted extraction with blanching pretreatment effect on bioactive compounds of green tea leaves ( Camellia sinensis ) powder

Abstract

Fresh green tea leaves have been considered by-products. They contain beneficial ingredients of polyphenols, approximately 30%. This study was aimed to investigate the blanching process combined with microwave-assisted extraction of green tea leaves. The best quality extract was obtained by blanching at 85°C for 45 s, then microwave-assisted extracting for 3 min with power of 16 W/g and frequency of 2450 MHz. The extract was added with whey protein isolate of 15%–15.3% and then spray-dried to form green tea powder. The highest antioxidant capacity was observed at 360.20 mg Trolox equivalent antioxidant capacity/g of tea powder. The bioactive compounds were determined as total polyphenol content of 336.65 mg GAE/g, epigallocatechin-gallate of 104.14 mg/g, epigallo-catechin of 62.15 mg/g, epicatechin-gallate of 22.09 mg/g, epicatechin of 19.27 mg/g, and caffeine of 3.13 mg/g. The tea powder was rich in chlorophyll content of 3.52 mg/g with nice green color and nutrition by abundant amino acids. Practical applications In Vietnam, fresh tea leaves, which are not in tea buds, have been often considered as by-products or even wastes. Our project investigated the extraction procedure for creating high-quality extract then used this extract for forming green tea powder by spray drying technology. The product obtained high content of total polyphenol, chlorophyll, and rich content of amino acids, which has better economic efficiency to use for the food or beverage industry in Vietnam.