Abstract: The dynamic changes of flavor compounds during the oxidation of coix seed oil were analyzed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and an electronic nose. The results showed that the characteristic volatile flavor compounds detected during the accelerated oxidation of coix seed oil were mainly aldehydes, ketones and alcohols. (E)-2-Nonenal, (E,E)-2,4-decadienal, (E)-2-decenal, (E,Z)-2,6-nonadienal, 1-octen-3-one, and decanal were the key flavor compounds of fresh coix seed oil, responsible for the grassy, oily, and watermelon-like smell of the oil. The deterioration of oil quality became more serious with the increase in oxidation time. The relative content of aldehydes was 73.815% after accelerated oxidation at 60 ℃ for 30 days, and the relative contents of small aldehydes, acids and alcohols were increased as compared with fresh oil. The key flavor compounds that were newly found in the accelerated oil included the newly added nonanal, octanal, hexanal, and (E)-2-octenal, which had a rancid odor due to the present of these compounds. Linear discriminant analysis (LDA) of the electronic nose data clearly distinguished the fresh oil from the oxidized oil, as well as between flavors in the early and late stages of oxidation. The characteristic compounds of fresh coix seed oil included (E)-2-nonenal, and (E,E)-2,4-decadienal. Small molecules, including nonanal, octanal, and hexanal, were the characteristic volatile compounds after accelerated oxidation of coix seed oil.

Key words: coix seed oil, solid phase microextraction-gas chromatography-mass spectrometry, electronic nose, linear discriminant analysis