Optimization of Supercritical CO₂ Extraction Process and Analysis of Physicochemical Properties of Coffee Essential Oil

Taking Baoshan small grain coffee beans from Yunnan Province as the object, the nutrient components of raw and cooked coffee beans were determined according to national standards. On the basis of single factor experiment, the process parameters of supercritical CO₂ extraction of coffee essential oil were optimized by response surface（RSM）. The physical and chemical indexes of the essential oil of raw and cooked coffee were determined. The fatty acid composition of raw and cooked coffee essential oil was analyzed by gas chromatography-hydrogen flame ionization detector (GC-FID). The results showed as follows: after roasting, the contents of water, water extract, caffeine, total sugar, crude fiber and crude fat in cooked coffee beans were significantly different from those in raw coffee beans (P<0.05); The optimum conditions of supercritical CO₂ extraction were as follows: extraction pressure 25 MPa, extraction temperature 54 ℃ and extraction time 150 min. Under these conditions, the extraction yield of raw coffee essential oil was 13.98%. Before and after roasting treatment, there was no significant difference in the routine physical and chemical indexes of coffee essential oil, and all of them met the requirements of national standards. 15 and 16 fatty acids were detected by GC-FID, among which linoleic acid, palmitic acid, stearic acid and oleic acid were the main fatty acids. Roasting had no significant effect on the fatty acid composition of coffee beans, but there were some differences in the content of each fatty acid. In this study, roasting has a certain degree of influence on the indicators of coffee beans and coffee essential oil, which provides a scientific basis for the development of coffee industry in Yunnan.