Identification and characterization of goat milk key flavor compounds and their precursors in electron beam irradiation and pasteurization on raw

The electron beam irradiation causes changes in goat milk flavor, which may arise from complex reactions such as fat oxidation. This study aimed to investigate the effects of electron beam irradiation and pasteurization on thiobarbituric acid reactive substance values and the fatty acid composition in goat milk. The multivariate analysis of aroma compounds in goat milk was performed using electron nose and Gas Chromatography and Mass Spectrometry (GC-MS). The results showed that both conventional heat treatments, including pasteurization and electron beam irradiation, resulted in fat content alteration in goat milk. The degree of fat oxidation was proportional to the irradiation dose, with a significant increase in saturated fatty acid content and a significant decrease in unsaturated fatty acid content after irradiation. The multivariate statistical analysis showed that the difference in flavor between milk treated with a high dose (5 kGy) of radiation and raw goat milk was larger. Further, 2,4-dimethyl-1-heptene, 3-methyl pentane, 3,3,5-trimethyl heptane, 2-pentanone, and 1-octene might be the characteristic substances accounting for the flavor difference between raw goat milk, pasteurized milk, and irradiated milk. C10:0, C12:0, C14:0, C16:1, C17:0, and C18:1n9t fatty acids might be the main precursors for the formation of off-flavors of irradiated milk. The results indicated that pasteurization and electron beam irradiation led to flavor alterations in goat milk, and high doses of irradiation might intensify fat oxidation and produce more flavoring compounds.