Volatile fingerprints and biomarkers of Chinese fragrant and non-fragrant japonica rice before and after cooking obtained by untargeted GC/MS-based metabolomics

Abstract

China has a rich resource of fragrant japonica rice that is gaining increasing consumers’ interests. In the present study, an untargeted gas chromatography-mass spectrometry-based metabolomics was employed to investigate the volatile profile of Chinese fragrant and non-fragrant japonica varieties. Partial least square discriminative analysis (PLS-DA) along with univariate analysis was taken to seek specific markers in raw and cooked Chinese japonica rice distinguishing fragrant and non-fragrant varieties. Volatile profile of raw Chinese japonica rice dominated by alkanes was completely different from that of cooked rice predominated by aldehydes. Thirteen and eleven volatile compounds were selected as the potential discriminative markers in raw and cooked Chinese japonica rice, respectively. Only 2-acetylpyrrole and decanal served as the specific marker in both raw and cooked Chinese japonica rice. Fragrant Chinese japonica rice varieties contained more 2-acetylpyrrole, (E)-2-octenal, nonanal, 1-tetradecene, decanal and (E)-2-decenal in raw rice. While fragrant Chinese japonica rice varieties contained more 2-acetyl-1-pyrroline, 2-acetylpyrrole, 1-hexanol, decanal and indole in cooked rice. The results provided an in-depth understanding of volatile variation in raw and cooked form of aromatic and non-aromatic cultivars and will benefit rice adulteration identification and marker-assisted flavor breeding in the future.