The chemical basis of aroma/taste and color formation in green tea infusion during cold brewing revealed by metabolomics analysis.

In this study, metabolomics and chemometrics were utilized to comprehensively investigate chemical mechanisms of aroma, taste, and color formation in cold-brewed green tea (4 °C). The results showed that the typical flavor of cold-brewed green tea (tea-to-water ratio: 1:50 g/mL) developed gradually after 1 h. Compared with the hot-brewed (80 °C) condition, volatile alcohols accumulated more under cold-brewing conditions. The extraction rate of bitter compounds such as caffeine decreased by more than 40 %, while the umami compound L-theanine increased about 9.2 % compared to hot-brewed green tea. The low temperatures also reduced flavonoid extraction ratio and retained high level of chlorophyll, resulting in a greener infusion. These differences led to cold-brewed green tea exhibiting a floral aroma, umami, sweet taste, and green color. This study revealed the impact of extraction temperature on the extraction efficiency of compounds from green tea. These findings can provide analysis methods for controlling quality of cold-brewed green tea.