Impact of enzymatic fermentation on taste, chemical compositions and in vitro antioxidant activities in Chinese teas using E-tongue, HPLC and amino acid analyzer
LWT(2022)
Abstract
Green, white and black teas showed different degrees in enzymatic fermentation through relevant processing procedures. To reveal the impact of enzymatic fermentation in tea-leaves, 44 chemical components including 17 phenolic compounds, 3 purine alkaloids, 19 free amino acids and γ-aminobutyric acid (GABA) in 27 various tea samples were determined by HPLC and amino acid analyzer, respectively. Additionally, E-tongue and 5 various assays were developed for taste evaluation and in vitro antioxidant activities analysis. Multivariate statistical analyses, such as PCA, HCA and PLS-DA (R2X = 1.000, R2Y = 0.932, Q2 = 0.908, respectively) divided theses teas into green, white and black tea categories, indicating the profound impact of enzymatic fermentation on tastes and chemical compositions. The enzymatic fermentation highly significantly (p < 0.001) promoted the decreases of 5 catechins (i.e. C, EC, GC, ECG and EGCG), gallic acid, rutin and 6 free amino acids, and the accumulations of 4 flavonoids (i.e. taxifolin, myricetin, queretin and luteolin), ellagic acid and 4 free amino acids in tea-leaves. The bivariate correlation analysis confirmed that 7 catechins, GG and 7 free amino acids might impress bitterness, umami and astringency, which also contributed to the antioxidant activities in tea-leaves. This study advanced the knowledge about enzymatic fermentation in tea-leaves processing.
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Key words
White tea,Electronic tongue,Partial least squares-discriminant analysis,Catechins,ABTS scavenging ability
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