Integrated volatilomics and metabolomics reveal the dynamic landscape and key transformation phases of flavor compounds in indica rice during hydrothermal cooking.

This study employed a novel approach combining GC × GC-O-MS-based volatilomics and UHPLC-MS/MS-based metabolomics to track the dynamic changes of volatile and non-volatile compounds during indica rice hydrothermal cooking. A total of 254 non-volatile metabolites changed significantly, with 63 identified as key differential metabolites (P < 0.05, VIP > 1.5), primarily lipids, organic acids, and heterocyclic compounds. The initial cooking stage (0-5 min) was critical for these changes. Volatilomics detected 107 volatile compounds: aldehydes, ketones, and heterocyclics increased gradually, while alcohols and esters decreased initially then increased. Based on OAV evaluation, 34 key aroma compounds (OAV > 1) were identified, with 2-acetyl-1-pyrroline, nonanal, (E)-2-nonenal, and (E,Z)-2,6-nonadienal contributing most significantly. Temporal analysis showed important changes in aroma during both initial and final stages (20-30 min). The initial phase was particularly crucial for metabolite and aroma transformation, involving both enzymatic and non-enzymatic reactions that collectively shape rice flavor. These findings offer valuable insights into aroma development during rice cooking.