Abstract:[Objective] This study aims to investigate the effect of exogenous enzyme treatment on the quality of summer green tea and optimize the enzyme treatment conditions. [Method] Sensory evaluation was employed to evaluate and screen the tea samples treated with six exogenous enzymes. The effects of cellulase, tannase, and treatment conditions on the sensory quality, bitter/astringent taste attributes, and main biochemical components of summer green tea were studied by electronic tongue and chemometrics methods. The optimal treatment conditions of cellulase and tannase were comprehensively evaluated by hierarchical cluster analysis, correlation analysis, and principal component analysis (PCA). [Result] Sensory evaluation revealed that cellulase and tannase significantly improved the flavor quality of tea samples. Electronic tongue and biochemical component analysis indicated that both enzyme treatments significantly reduced the predicted mass concentrations of bitterness/astringency as well as the mass fractions of tea polyphenols and ester-type catechins (ETC) while increasing the levels of soluble sugars, non-ester-type catechins (NEC), and gallic acid (GA). Moreover, tannase demonstrated a superior effect compared with cellulase. Hierarchical cluster analysis and PCA showed significant difference between exogenous enzyme-treated tea samples and control tea samples. Predicted mass concentrations of astringency and sensory score were identified as key factors affecting the overall quality of tea samples. The optimal treatment conditions of cellulase and tannase were enzyme concentration of 30 U/mL, solid-to-liquid ratio of 1 kg:20 mL, and treatment time of 40 min. [Conclusion] The results of this study can provide theoretical support for improving the taste quality of summer green tea with exogenous enzymes and the utilization of fresh summer tea leaves.
