Analysis On Chemical Components Of Bitterness And Astringency In Green Tea & Interaction Between Taste-Active Components

The bitterness and astringency are very important for describing the quality of tea.Spring green tea taste as mellow and umami,but it is hard for consumers to accept summer and autumn green tea because of its more bitter and astringent taste.It is significant to study the bitter and astringent chemical components in green tea and interactions among taste constituents for improving the taste of tea and utilization of summer and autumn tea.Many researchs have showed that caffeine and catechins are key factors for bitterness and astringency,in addition,glutamic acid and theanine help to weak bitterness and astringency of tea.However,the mechanism of amino acids to bitterness and astringency is unclear and how to evalue the intensity of bitterness and astringency quantitively is still confused by people.In this study,catechins,caffeine and amino acids in 121 green tea with different regions and seasons were analyzed by HPLC to confirmed the taste factors combined with mathematical analysis.Moreover,the influence of amino acids on green tea taste and the effects of amino acids to EGCG and caffeine flavor properties has been explored using quantitative sensory assessment,electronic tongue,coomassie brilliant blue method and SDS-PAGE technology.The results are as following:(1)Main factors for characterising green tea taste were confirmed.5 taste complex factor such as F1: bitter,F2: umami,F3: astringent,F4: sour,F5: fresh obtained by PCA and factor analysis could preferably explain flavor characteristics such as bitterness,astringency,and umami.This method also applies to other tea;(2)Different amino acids take different efffect on bitter and astringent taste.The effects of various amino acids to green tea liquor,EGCG and caffeine were quantitatively evaluated by sensory analysis,electronic tongue,coomassie brilliant blue method,SDS-PAGE and HPLC.These results indicated that glutamic,theanine,aspartic acid,arginine and glycine could weaken the intensity of astringency and the ability fits,and the diminished capacity showed negative correlation with threshold of these amino acids;(3)Developed a new method for exploring astringency of tea soup.SPI and SAPI to represent the setting power of samples to salivary proteins were proposed by measuring the combining degree of polyphenols with salivary proteins and evaluating astringency of tea soup or astringent composition.This could also filter new compositions which influencethe astringency of tea.