Fatty Acid Composition and Basic Physicochemical Attributes of Persian Walnut Oil as Affected by Different Extraction Methods

In this study, the effect of three various extraction methods (Hexane, Modified Bligh–Dyer and cold-press) on oil yield, fatty acids profile, and physical and chemical properties of the walnut oil was investigated. Result showed that crude oil extracted by Modified Bligh–Dyer method had the highest yield (37.33%) followed by hexane (55.85%) and cold-press extraction method (34.93%), respectively (p<0.01). The fatty acids content was not influenced by extraction method. The oleic acid content ofthe oils ranged from 24.23 to 25.17% of the total fatty acids while the linoleic acid and linolenic contents ranged from 50.11 to 50.18%% and 12.04 to 12.07% respectively. The physicochemical properties analysis demonstrated that the Modified Bligh–Dyer method was considered to be the optimum process for extracting walnut oil with a higher quality with respect to the other two methods. A high positively correlation was found between Rancimat values and percentages of oleic acid (r = 0.52, p<0.01), but negatively correlated with linolenic acid content (r = -0.63, p<0.01). Moreover, the oil extracted from Hexane method had more hydroperoxides and secondary products than the obtained oil from other extraction methods.

Keywords:

Walnut oil , Fatty acid composition , Extraction method , Oil stability , Iodine value