Physicochemical Properties and Volatile Profiles of Cold-Pressed Trichosanthes kirilowii Maxim Seed Oils

The physicochemical properties and volatile profiles of cold-pressed Trichosanthes kirilowii Maxim (T. kirilowii) seed oils from four regions in China were determined in this study. The total oil content and cold-pressed oil yield of the four different sourced seeds were 38.06–44.33% and 15.17–30.97%, respectively. All the cold-pressed oil samples were found to be rich in polyunsaturated fatty acids, with content ranging from 45.41 to 75.32% of the total fatty acids. Punicic, α-eleostearic and catalpic acids were the main conjugated linolenic acid isomers in the cold-pressed T. kirilowii seed oils. The results of melting and crystallization profiles indicated that each oil sample exhibited different transitions steps due to its triacylglycerol composition, crystal structure and total unsaturation. Analysis of volatile profiles showed that 2,4-nonadienal was one of the most important aldehydes in the cold-pressed T. kirilowii seed oils, and less short chain acids (0.20%) but more esters (5.48%) were found in the sample with high content of punicic acid (Hebei sample). Results of oil quality indices indicated that cold-pressed T. kirilowii seed oils were liable to be oxidized, and their stabilities reduced with the increase of acid values. In general, more attention should be paid to improve the oxidative stability of cold-pressed T. kirilowii seed oils in their further application in food industry.