A study was carried out to evaluate oil contents, fatty acid composition and tocopherol contents of several walnut types in relation to roasting process. The major fatty acid identified was linoleic acid in both roasted and unroasted walnut oils. Linoleic acid contents of unroasted walnut oil varied from 46.44 (Type 9) and 63.59% (Type 7), while the linoleic acid contents of roasted walnut oils at 120℃/h ranged from 55.95% (Type 3) to 64.86% (Type 10). Interestingly, linolenic acid contents of both roasted and unroasted oils changed between 9.43 (Type 10) and 16.29% (Type 8) to 9.64 (Type 10) and 16.58% (Type 8), respectively and were significant (p < 0.05) different. γ-tocopherol content of unroasted walnut oils varied between 6.3 (Type 3) and 11.4 mg/100g (Type 1) and γ-tocopherol contents of roasted walnut oils ranged between 28.1 (Type 8) and 38.2 mg/100g (Type 3). The oil could be useful for industrial applications owing to good physicochemical properties. Fatty acid values for oil obtained from roasted walnut were slightly higher than those reported for unroasted walnut oils.
Keywords: GC; HPLC; fatty acid; oil; roasting; tocopherol; walnut kernel.