Chemical Compositions of Walnut (Juglans regia L.) Oils from Different Cultivated Regions in China

This study is a comprehensive report on the quality of Chinese walnut oil, which enriches the research of oil resources. A total of 16 walnut samples from China were selected, and walnut oils were obtained using the pressing process. The lipid compositions and micronutrient contents were analyzed. The fatty acids corresponded to palmitic acid (3.05-8.25%), oleic acid (12.56-26.03%), linoleic acid (51.21-68.97%), and linolenic acid (6.83-15.01%), and the main triacylglycerols were trilinolein (27.87-39.47%), followed by oleoyl-linoleoyl-linolenoyl-glycerol (17.07-24.18%), dilinoleoyl-oleoyl-glycerol (9.65-15.46%), palmitoyl-dilinoleoyl-glycerol (5.96-14.98%), and dilinoleoyl-linolenoyl-glycerol (6.42-12.43%). In addition, high amounts of micronutrients, including phytosterol, squalene, tocopherol, and total phenolic content, were found in walnut oils ranging from 540 to 1594, 17 to 131, 345 to 1280, and 1.04 to 20.39 mg kg(-1) among different samples, respectively. The differences in the geographical location and climate caused different regions of cultivation, which resulted in the differences in the chemical composition of walnut oil. Further multiple linear regression analyses between oxidative stability indices, fatty-acid compositions, and micronutrients revealed that linoleic acid (R = -0.891; P < 0.05), -tocopherol (R = 0.713; P < 0.05), and total phenolic content (R = 0.369; P < 0.05) were the main factors that affect the oxidative stability of the walnut oil.