Effect of brewing conditions on the chemical and sensory profiles of milk tea

Abstract

The brewing conditions of beverage milk tea determine the taste of milk tea. This study investigated the changes in sensory characteristics and small molecule compounds in milk tea made from large-leaf yellow tea under different brewing conditions by sensory analysis, colorimeter, and LC-MS. The results show that the tea to milk ratio is the most important process affecting the taste, and the color values of b* (+yellow, - blue) can be used to evaluate the taste of milk tea made from large leaf yellow tea. The composition of small molecular compounds is affected by tea to milk ratio, which can change the taste of milk tea. l-cysteine and 8-methylsulfinyloctyl glucosinolate are significantly positively correlated with taste by metabolomics analysis. l-cysteine was used to verify the analysis results by LC-MS. The total acceptance of milk tea is improved by adding l-cysteine at a low level (0.025-0.035 mM).

Keywords: Color; Large leaf yellow tea; Milk tea; Non-targeted metabolomics; Response surface methodology; l-cysteine.

Fig. 1

Surface and contour plots for the effect of different variables on taste profiles with significant (p < 0.05). Effects of (a)(b) temperature and tea: milk ratio on bitterness, (c)(d) temperature and tea: water ratio on sweetness, (e)(f) temperature and tea: milk ratio on sweetness, (g)(h) temperature and tea: milk ratio on total acceptance.

Fig. 2

Taste wheel of milk tea (Large-leaf yellow tea). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Effect of different production conditions to the color of milk tea. (a) Images of 30 milk tea samples (from top left Sample 1) down the columns to the bottom right Sample 30). (b) Color of 30 milk tea samples made under different conditions and with different recipes. (c) Effect of different parameters during processing on the color of milk teas. (d) Correlation between taste and color of milk tea.

Fig. 4

Multivariate statistical analysis of milk tea mixed with different tea: milk ratios; (a): Principal component analysis score chart (PCA); (b): Orthogonal partial least squares discriminant analysis (OPLS-DA); (c): Heat map and hierarchical clustering of the levels of non-volatile compound in milk tea mixed with different tea: milk ratios; (d): Pearson correlation analysis of chemical composition of major differential metabolites and sensory perception of taste in LYT milk tea.

Fig. 5

Taste profile evaluations of samples with additional l-cysteine. (a) LYT tea samples; (b) LYT tea milk tea samples. Points with * are significantly different (P < 0.05), ** are extremely different (P < 0.01), and without * are not significantly different (P < 0.05).