Evolution of Fatty Acid Composition, Volatile Flavors and Bioactive Ingredients of Coffee Oil during Coffee Bean Roasting

In this study, the physicochemical properties, fatty acid composition, volatile components and bioactive ingredients of oil from Arabica coffee beans from Yunnan roasted for different periods were systematically investigated. The results showed that as the degree of roasting increased, the color of the oil deepened, the acid value showed an increasing trend from 1.60 to 3.75 mg/g, the iodine value decreased from 142.04 to 83.12 mg/100 g, the anisidine value first increased and then decreased, ranging from 3.40 to 16.26, and the saponification value decreased slightly but not significantly. A total of 11 fatty acids were identified, the most predominant being linoleic acid, whose content ranged from 43.06% to 64.39%, followed by stearic and palmitic acids with contents ranging from 12.67% to 27.55% and oleic acid in the range of 9.03% to 17.20%. The effect of roasting degree on the type of fatty acid was not significant, but there were some differences in the content of fatty acid. A total of 25, 33, 36, 53, 54, 59, 64 and 58 volatile components were identified in oils from coffee beans roasted to eight different degrees from JQ to FZ, respectively. The major volatile components were furans, pyrazines, ketones and pyrroles, whose type and content showed a decreasing trend. The contents of bioactive ingredients including kahweol, α-tocopherol, γ-tocopherol and δ-tocopherol decreased, while the total phenolic content increased continuously from 7.75 to 15.96 mg/100 g. The results of this study provide a theoretical basis and technical support for the fine and deep processing and high-value utilization of coffee beans.