Impact of enzymatic fermentation on taste, chemical compositions and in vitro antioxidant activities in Chinese teas using E-tongue, HPLC and amino acid analyzer

• Published in: Food science & technology Vol. 163; p. 113549
• Main Authors: Zhou, Binxing, Ma, Bingsong, Xu, Chengcheng, Wang, Jiacai, Wang, Zihao, Huang, Youyi, Ma, Cunqiang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.06.2022
• Subjects: ABTS scavenging ability; Catechins; Electronic tongue; Partial least squares-discriminant analysis; White tea; ABTS scavenging ability; Catechins; White tea; Electronic tongue; Partial least squares-discriminant analysis
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2022.113549

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. •Enzymatic fermentation caused the chemical differences among green, white and black teas.•Enzymatic fermentation significantly impact 5 catechins,5 flavonoids, 6 free amino acids.•Slight enzymatic fermentation might improve the in vitro antioxidant activities in tea-leaves.•Catechins, free amino acids contributed to antioxidant activities, bitterness, umami, astringency.