Determination of fatty acid and tocopherol compositions and the oxidative stability of walnut (Juglans regia L.) cultivars grown in Serbia

Abstract

Five cultivars (Sampion, Jupiter, Sejnovo, Elit, and Geisenheim 139) of walnuts (Juglans regia L.) were collected during the 2008 harvest, from Cacak, Central Serbia. Two techniques of oil extraction were implemented - cold pressing and organic solvent extraction. The influence of the implemented methods on the fatty acid composition, tocopherol content as well as oxidative stability was examined. Predominant fatty acids were palmitic, oleic, linoleic, and linolenic acids. The oleic acid content of the oils ranged from 15.9-23.7% of the total fatty acids, while the linoleic acid content ranged from 57.2-65.1% and that of linolenic acid from 9.1-13.6%. The process of oil extraction had no significant effect on the content and composition of fatty acids in the oil. The total content of tocopherols ranged from 28.40 mg/100 g to 42.40 mg/100 g of the extracted oil. The most common tocopherol in all samples was γ-tocopherol. The oil extracted using the Soxhlet method contained higher amounts of total tocopherols while the stability of the oil samples, expresed as induction period, ranged from 5.0 h to 7.1 hours. Reduced stability of the oil samples as measured by the Rancimat method was negatively correlated with the level of linolenic acid and total content of tocopherols.