BACKGROUND: Alterations in the degrees of milling (DOM) could significantly influence the odor of rice. A gas chromatography-mass spectrometry (GC-MS)-based untargeted metabolomics method has been effectively employed to identify the differential volatiles among rice from various origins or varieties, although it has not been utilized to identify the differential volatiles among cooked rice with different DOM. RESULTS: Fifty volatile compounds were detected in cooked brown rice (CBR), cooked medium-milled rice (CMMR) and cooked well-milled rice (CWMR) of the four fragrant Simiao rice by GC-MS. A comprehensive GC-MS-based untargeted metabolomics analysis revealed 25 differential volatiles among CBR, CMMR and CWMR. Among them, seven differential volatiles, namely hexanal, octanal, decanal, (E,E)-2,4-decadienal, vanillin, acetoin and pentanol, as well as one differential volatile (dibutyl phthalate), were determined as volatile markers for CBR and CMMR, respectively. Moreover, acetoin was identified to distinguish among CBR, CMMR, and CWMR of fragrant Simiao rice. CONCLUSION: GC-MS-based untargeted metabolomics could be effectively applied to screen differential volatiles in cooked rice with different DOM. The 25 differential volatiles identified could significantly contribute to the distinctive odor in cooked fragrant Simiao rice with different DOM. © 2024 Society of Chemical Industry.