L cysteine

L-Cysteine, D-glucose, nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal, (E,Z)-2,6-nonadienal, 1,2-dichlorobenzene, and the n-alkanes (C₅–C₃₀) were purchasing from J&K Chemical Ltd. (99%, Beijing, China). Dichloromethane, PBS (phosphate buffer, 0.2 M, pH 6.50), Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Stand compounds including: 1-hexanethiol (98%), 2-hexylthiophene (98%), 2-propylthiophene (98%), 3,4-dimethylthiophene (98%), 2-butylthiophene (98%), 2-pentylthiophene (98%), 2-pentylfuran (95%), 2-methylpyridine (98%), 5-methyl-2-thiophenecarboxaldehyde (99%), thieno[3,2-b]thiophene (98%), thieno[2,3-b]thiophene (98%), 2-propylthiazole (99%), 2-ethylthiazole (98%), 2-thiophenecarboxaldehyde (98%), and other lipid degradation products (J & K Chemical Co., Ltd. Beijing, China).

Flaxseeds were procured from the local market of Xi’an city, Shaanxi, China. Defatted flaxseed meal was prepared by removing the oil from flaxseed, according to Wei et al. (2018) (link). To identify the generated volatile flavor compounds, l-Cysteine (99%), d-xylose (98%), and the standard compounds (≥95%) were purchased from J&K Chemical Ltd. (Beijing, China). The n-alkanes (C₇-C₃₀) for retention indices and 1,2-dichlorobenzene for quantification were purchased from Sigma-Aldrich (Shanghai, China).