Effect of Yellowing Duration on the Chemical Profile of Yellow Tea and the Associations with Sensory Traits

Abstract

The yellowing process is the crucial step to form the characteristic sensory and chemical properties of yellow tea. To investigate the chemical changes and the associations with sensory traits during yellowing, yellow teas with different yellowing times (0–13 h) were prepared for sensory evaluation and chemical analysis. The intensities of umami and green-tea aroma were reduced whereas sweet taste, mellow taste and sweet aroma were increased under long-term yellowing treatment. A total of 230 chemical constituents were determined, among which 25 non-volatiles and 42 volatiles were the key chemical contributors to sensory traits based on orthogonal partial least squares discrimination analysis (OPLS-DA), multiple factor analysis (MFA) and multidimensional alignment (MDA) analysis. The decrease in catechins, flavonol glycosides and caffeine and the increase in certain amino acids contributed to the elevated sweet taste and mellow taste. The sweet, woody and herbal odorants and the fermented and fatty odorants were the key contributors to the characteristic sensory feature of yellow tea with sweet aroma and over-oxidation aroma, including 7 ketones, 5 alcohols, 1 aldehyde, 5 acids, 4 esters, 5 hydrocarbons, 1 phenolic compound and 1 sulfocompound. This study reveals the sensory trait-related chemical changes in the yellowing process of tea, which provides a theoretical basis for the optimization of the yellowing process and quality control of yellow tea.

Tea Quality of the Mysterious “Dahongpao Mother Tree” (Camellia sinensis)

“…Based on the above analysis, further analysis of the importance of 16 categories of characteristic metabolites in the process of distinguishing MD from PD using TOPSIS revealed (Figure 5E) that 8 categories had a weight of 10% or more in the process of distinguishing MD from PD, namely phenolic acids (100%), amino acids and derivatives (35.31%), flavones (33.98%), tannin (31.08%), flavonols (31.06%), flavanols (31.02%), organic acids (30.88%), and others (28.06%). The main taste characteristic reported for phenolic acids and tannin is bitterness [32,33]. Flavones, flavonols, and flavanols are also characterized by bitterness [34,35].…”

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

“…Most free amino acids ( e.g ., theanine, glutamic acid, glutamine, valine, leucine, isoleucine, aspartic acid, and asparagine) showed a upward trend in contents during yellowing for 0–8 h, while during further yellowing, their contents remarkably declined, which might result in the increase of their derivatives such as the betaine and pipecolic acid isomers (Wei et al., 2022). Flavonoid glycosides, GBVs, and some phenolic acids showed downward trend in their levels (Table 2) (Fan et al., 2022; Wei et al., 2021). In addition to these changes of non‐volatiles, yellowing also decreased the levels of some volatiles that contributed to the grassy, floral and fruity aromas such as ( Z )−3‐hexen‐1‐ol, 1‐hexanol, pentanal, heptanal, and 1‐octanol, while simultaneously increased the levels of mushroom‐ and sweet‐like aroma compounds like 1‐octen‐3‐ol, benzene‐acetaldehyde, and β‐ionone (Wei et al., 2022).…”

“…In addition to these changes of non‐volatiles, yellowing also decreased the levels of some volatiles that contributed to the grassy, floral and fruity aromas such as ( Z )−3‐hexen‐1‐ol, 1‐hexanol, pentanal, heptanal, and 1‐octanol, while simultaneously increased the levels of mushroom‐ and sweet‐like aroma compounds like 1‐octen‐3‐ol, benzene‐acetaldehyde, and β‐ionone (Wei et al., 2022). Furthermore, the influence factors that constrained the yellowing degree were thought to be temperature, time, and moisture content throughout the yellowing process (Fan et al., 2022; Wei et al., 2021; Xu et al., 2018).…”

Tea as a natural gift for discovering antiviral candidates

“…Yellow tea contains catechins, flavonoids, alkaloids, amino acids, and other ingredients [15] . The initial process is the same as that of green tea regarding to roasting or steaming, and it then requires a unique step known as "sealed yellowing" that can remove the grassy flavor of green tea while still retaining the healthcare values [16] .…”