Amino acids

Four brands of commercial Huangjiu A, B, C, and D (14% vol.) were purchased from a local supermarket in Beijing. The edible alcohol (14% vol.) was purchased from Azelis Co., Ltd. Glucose and maltose were purchased from Yuanye Biotechnology Co., Ltd. Amino acids were purchased from Sigma‐Aldrich. Putrescine, 2‐phenylethylamine, cadaverine, histamine, tyramine, fusel oil, and acetaldehyde were purchased from Banxia Biotechnology Co., Ltd. Ethyl lactate, ethyl acetate, diethyl succinate, vanillic acid, lactic acid, succinic acid, acetic acid, phenylacetaldehyde, furfural, vitamins C, Ca, K, and Mg were purchased from Sinopharm Chemical Reagent Co., Ltd. The 5‐HT, 5‐HIAA, DA, and NO detection kits were purchased from Nanjing Jiancheng Biological Engineering Co., Ltd. A high‐purity total RNA rapid extraction kit was purchased from Beijing Biotech Biotechnology Co., Ltd. A ReverTra Ace® qPCR RT Master Mix kit was purchased from Toyobo Co., Ltd. Real‐time fluorescent quantitative primers were supplied from Beijing Huada Gene Research Center. All other chemical reagents were of analytical grade.

One bud and one leave of “CuiFeng” were selected in this study, and picked in April 2020 in KaiHua (Zhejiang, China).
All the chromatography-grade standards, such as catechins, amino acids, flavonoid glycosides, gallic acid, and caffeine were purchased from Shanghai Yuanye Biological Technology Company (Shanghai, China). The purity of these chemical standards was ≥ 98%.