Effect of milling degree on volatile profiles of cooked rice determined by electronic nose and HS-SPME-GC-MS

Background and Objectives: Volatile components are mainly distributed in the rice bran layer; thus, rice with different milling levels exhibit different volatile profiles, which affects the aroma of rice and cooked rice. Seven diverse rice varieties were investigated to explore the effect of milling degree on volatile profiles of cooked rice, odor activity value (OAV) was applied to identify key aroma compounds, and partial least squares discriminant analysis (PLS-DA) was applied to determine important marker compounds that may affect aroma.Findings: The volatile profiles of cooked rice with different milling times were different according to the result of electronic nose. A total of 82 volatiles were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry. The number and total content of volatile compounds in most samples decreased with increasing milling time. The number of key aroma compounds (OAV > 1) in most samples also showed a decreasing trend with increasing milling time. PLS-DA model successfully discriminated the differential volatile compounds in cooked rice samples with different milling times. Tridecane, 6-methyl-5-heptene-2-one, nonanal, decanal, 2-butyl-2-octenal, pentadecanal, 2,4-decadienal, anethole, geranylacetone, 1-dodecanol, 2-pentadecanone, 2-methoxy-4-vinylphenol, and indole were identified as 13 marker aroma-active compounds.Conclusions: The effect of milling degree on the volatile profiles of cooked rice was closely related to the rice varieties. Longer milling time was not in favor of the aroma of cooked rice. Milling degree mainly affected the nutty, citrus, fruity, waxy, herbal, fatty, celery, smoky, and floral aromas of cooked rice.Significance and NoveltyThe study provided important information for understanding the impacts of milling degree on volatile compounds and aroma properties of cooked rice. This is of great significance for advocating moderate processing of rice and regulating the aroma quality of cooked rice.