Determination of Fatty Acids in Rice Oil by Gas Chromatography-Mass Spectrometry (GC-MS) with Geographic and Varietal Discrimination by Supervised Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA)

Rice is a major crop and the main staple for more than half of the world's population. With the continuous improvement of the living standard, people pay more attention to the taste, flavor, and nutrition of rice. In this study, a one-step method was used to derivatize the free fatty acids and glyceride fatty acids in rice oil with determination by gas chromatography-mass spectrometry (GC-MS). Rice varieties cultivated in Guangdong and Hunan, including Xiangwanxian 17, Huanghuazhan, Xiangwanxian 13, and Nongxiang 32, were analyzed by this method. The results showed that the main components in rice oil include palmitic acid (29.80-21.41%), oleic acid (33.81-38.29%), and linoleic acid (25.17-31.40%). The content of unsaturated fatty acids (69.41-72.55%) was higher than for saturated fatty acids (27.45-30.59%). Supervised orthogonal partial least squares discriminant analysis (OPLS-DA) was used to identify the differences in the fatty acids in rice oil from different locations and varieties. There are small differences among rice varieties cultivated in the same locations and larger differences between the same varieties from different locations. According to the results from Student's t-test and variable importance in projection (VIP) value of the OPLS-DA model, the contents of myristic acid, stearic acid, palmitoleic acid, and arachidic acid were significantly affected by the location (p < 0.05 and VIP > 1). These results provide useful information for the further development and utilization of rice resources.