关键词: 乙酯型金枪鱼油, 分子蒸馏, 气相色谱-质谱联用, 电子鼻, 红外光谱仪

Abstract: Ethyl ester type tuna oil, a high-quality oil obtained after multi-stage molecular distillation of crude tuna oil, is rich in polyunsaturated fatty acids, being colorless and tasteless. During the process, a series of changes may occur. In this paper, gas chromatography-mass spectrometry (GC-MS), electronic nose, and Fourier transform infrared (FTIR) spectroscopy were used to detect tuna oil fractions from different stages of molecular distillation for differences in composition, flavor and properties as well as identification of the main volatile substances. The results showed that the contents of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in fish oil were increased at first, reaching a maximum of 74.10% and 31.41%, respectively and then decreased during the distillation process. The second distillation stage yielded ethyl ester type tuna oil having a total content DHA and EPA of up to 84.26%, which was significantly higher than that of the third, fourth and fifth distillation stage. Electronic nose detection indicated significant differences in the volatile composition of crude fish oil and its distillation fractions. The major flavor components of the different distillation fractions were hexanal, octanal, heptanal and nonanal, 1-octen-3-ol demonstrated, 2-11 ketone, 2-pentyl-furan, which together contributed to the fishy, earth/ muddy and greasy odors, fatty flavor, grassy, vegetable and mushroom aromas. The results of infrared spectroscopy showed that the contents of the main components of the distillation fractions of tuna oil were different. The fractions from the first and second stages contained the largest number of lipid components, showing the highest enrichment effect, which was significantly higher than that of the third, fourth and fifth distillation stage.

Key words: ethyl ester type tuna oil, molecular distillation, gas chromatography-mass spectrometry, electronic nose; infrared spectroscopy