Effect of spreading time on the taste quality of steamed green tea based on E-tongue evaluation and chemometric statistical analysis

Processing plays a decisive role in the flavor of steamed green tea (SGT), especially spreading, which is the basis of its taste formation. However, the effect of spreading time on the taste quality of ‘Qiancha 1’ (Camellia sinensisvar. sinensis) steamed green tea (QSGT) has not been reported. In this study, fresh leaves from ‘Qiancha 1’ were made into SGTs after spreading at different times and evaluated using a chromatographic method combined with an electronic tongue (E-tongue) and sensory evaluation, using ‘Huacha 1’ (Camellia sinensisvar. sinensis) steamed green tea (HSGT) as the control. Galloylated catechins were transformed to non-galloylated catechins more drastically in ‘Huacha 1’ than in ‘Qiancha 1’ during spreading. QSGT made from fresh leaves after 6 h of spreading was among the best with umami and mellow tastes in the sensory evaluation, and QSGT had higher bitter, astringent, umami, and sweet taste values than HSGT in the E-tongue evaluation. In QSGT, l-theanine, l-glutamate (Glu), (−)-epigallocatechin-3-gallate (EGCG), l-histidine (His), and l-methionine (Met) were the predominant compounds for umami, bitter, and astringent tastes, while in HSGT, l-theanine, Glu, EGCG, His, Met, and l-arginine (Arg) were predominant. The principal component analysis and orthogonal partial least squares discriminant analyzes further revealed that differences in the metabolism of polyphenols contributing to the formation of bitter and astringency tastes were essential indicators for distinguishing SGTs made from different spreading times and cultivars. Overall, this study provides an approach for the enhancement of taste in SGT using the personalized processing method for different tea cultivars.