Analysis of the key aroma volatile compounds in rice bran during storage and processing via HS-SPME GC/MS

Rice bran is one of the most valuable nutritional byproducts of rice milling. It is known to have an unacceptable flavor to consumers, so the development of reliable analytical methods to determine its unpleasant volatile compounds should be developed. Comparative volatile profiling of rice bran at different times of accelerated storage was performed using solid-phase microextraction (SPME) coupled to GC/MS, and the impact of stabilizing methods on the odor of rice bran was evaluated using E-nose, GC/MS and gas chromatography-olfactometry (GC-O) analyses. Sixty-five volatile compounds were identified and classified into six groups. Among them, the relative concentration of aldehydes increased with storage time, and hexanal was the compound with the highest content. Similar behavior was exhibited by ketones and alcohols, which were connected with early oxidation of rice bran. The main characteristic odor compounds of rice bran were vanillin, 2-methoxy-4-vinylphenol and 5-amino-2-methoxyphenol regarding ferulic acid. Through PCA, the volatile compounds of six kinds of rice bran were distinguished. The GC-O experiment verified that the processed products changed from the original grassy, oily flavor to vanilla, cheese, and caramel flavors. These results comprehensively elucidate the flavor characteristics of rice bran and provide important theoretical support for the development of rice bran products.