Abstract:In order to investigate the effects of different membrane separation processes on product quality, biochemical components and antioxidant activity in vitro, the water extract of Oolong tea was separated by ceramic membrane (500 nm) and ultrafiltration membrane (20, 10, 5, 3.5 kD), and tea powder was prepared by spray drying. The quality of tea powder prepared by different membrane separation processes was evaluated through sensory quality and physical properties, and the main biochemical components of tea powder were analyzed and compared. Meanwhile, the antioxidant activity of tea powder in vitro was evaluated by DPPH radical scavenging capacity, the ferric ion reducing antioxidant power (FRAP), hydroxyl radical scavenging capacity and anti- superoxide anion activity. The results showed that the sensory quality and antioxidant activity of ceramic membrane were the highest. The 500 nm ceramic membrane can effectively separate and enrich tea polyphenols (TPs), free amino acids (FAAs), caffeine (CAF), soluble sugar (SPS) and other substances, but also achieve the effect of impurity removal. The water extract of Oolong tea separated by ceramic membrane and then separated by ultrafiltration membrane, TPs, CAF, SPS, catechin components have no separation and enrichment effect. Ultra- filtration membranes with molecular weight less than 10 kDa can effectively separate and enrich free amino acids. The 500 nm ceramic membrane interception solution had the highest SPS content, but the worst sensory quality and the lowest antioxidant activity. Therefore, considering the three factors of quality, efficiency and energy saving, the comprehensive quality of tea powder prepared by 500 nm ceramic membrane through liquid is the best.
