Bioscience Evidence 2026, Vol.16, No.4, 235-248 http://bioscipublisher.com/index.php/be 237 which are closely associated with bitterness and astringency, showed the greatest increases. Using an electronic tongue system, Li et al. (2025a) found that summer Lu'an Guapian tea had significantly higher bitterness and astringency but lower umami than spring tea (Figure 1). Ma et al. (2022) further demonstrated that flavonoid biosynthesis was enhanced during summer, whereas umami-related amino acids decreased, providing a metabolic explanation for the stronger bitterness of summer tea. Although summer tea is less fresh than spring tea, its high concentrations of polyphenols and catechins provide considerable processing potential. Liang et al. (2024) suggested that summer tea is well suited for producing black tea, functional teas, and food ingredients through fermentation. During processing, polyphenols are converted into quality-related compounds such as theaflavins and thearubigins, which reduce bitterness and improve aroma. Cultivation practices can also improve summer tea quality. For example, appropriate nitrogen fertilization can increase total polyphenols, catechins, and caffeine while improving the chemical composition of fresh leaves, making them more suitable for different processing purposes. The value of summer tea does not lie in competing with spring tea. Instead, its high polyphenol content and rich bioactive compounds make it an excellent raw material for black tea, fermented tea, tea beverages, and functional foods through targeted processing and product diversification. Figure 1 Processing flow and sensory quality of Lu'an Guapian tea in different seasons. (A) Processing flow charts of Lu'an Guapian tea. Spring tea (SPT), Summer tea (SUT), Autumn tea (AUT). (B) The colorimetric values of SPT, SUT, and AUT tea infusions. Errors bars represent mean ± SD. Different letters indicate a significant difference at the 0.05 level, as determined by one-way ANOVA and Tukey's post-hoc test. (C) Radar chart for quantitative descriptive analysis of taste and E-tongue analysis (Adopted from Li et al., 2025a) 2.3 Quality characteristics of autumn tea The quality of autumn tea generally falls between that of spring and summer tea, although considerable variation exists among tea types and growing environments. Autumn tea usually contains fewer umami compounds than
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