Characterization of the Changes in Volatile Flavor Substances of Rice and Rice Bran With Different DOM by HS-SPME-GC-MS and HS-GC-IMS.

A combined headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) approach was employed to examine changes in volatile organic compounds (VOCs) in rice and rice bran across different degrees of milling (DOM) and to identify characteristic VOCs. A total of 43 and 63 VOCs were detected in rice samples using HS-SPME-GC-MS and HS-GC-IMS, respectively, while 73 and 63 VOCs were identified in rice bran. With increasing DOM, the VOC content in both rice and rice bran showed a fluctuating trend, initially decreasing, then increasing, and finally declining, with peak levels observed in samples R-3 and B-4, respectively. Based on odor activity value (OAV) analysis, 13 and 20 key VOCs were identified in rice and rice bran, respectively, among which 2-acetyl-1-pyrroline, (E)-2-nonene, and (E, E)-2,4-decadienal were the most influential compounds. Principal component analysis and partial least squares discriminant analysis (PLS-DA) successfully distinguished rice and rice bran with different DOM based on their changes in VOCs. PLS-DA further identified 7 VOCs with OAV > 1 as key VOCs of rice at different DOM. Similarly, 8 VOCs with OAV > 1 were identified as key VOCs for rice bran. From the perspective of aroma compound content, sample R-3 represented the optimal DOM. Moreover, B-4, corresponding to the outermost layer of R-3, played a significant role in shaping its flavor profile. PRACTICAL APPLICATIONS: The findings indicated that the DOM governed both the retention and generation of VOCs, significantly shaping the overall VOC profile and flavor characteristics of rice and rice bran. These results established a theoretical basis for understanding how milling precision affects rice flavor quality.