Evaluation of different degree of ripeness and sun-drying process on triacylglycerols composition of Pistacia vera L. Oil

This paper reports the composition of triacylglycerols (TGs) and the fatty acids (FAs) distribution of oil extracted from pistachio kernels at different degree of ripeness (unripe and ripe). Moreover, the effect of sun-drying process was investigated. TGs account for more than 90% of the total glycerolipids content. The main TGs founded in the P. vera oil were: LLL, OLL, LLP, OLO, OLP, OOO and OOP; these accounted for more than 80% of the total TGs content. The mean content of TGs with more polyunsaturated fatty acids (LLLn, LLL, OLLn, LnLP, OLL and LLP) was lower in ripe (29.4%) and dried ripe (29.1%) kernels respect to unripe (32.9%). The FAs detected in the TGs were palmitic (P), margaroleic (Mo), stearic (S), oleic (O), linoleic (L), linolenic (Ln) and gadoleic (G). The saturated FAs, represented by P (C16:0) and S (C18:0) did not change significantly both with ripeness and drying process, being 13.9% in unripe samples, 13.8% in ripe samples and 14.0% in dried ripe samples of the total fatty acids composition. Monounsaturated FAs represented by Mo (C17:1), O (C18:1) and G (C20:1) accounted for 49.5% in unripe kernels, 52.7% in ripe kernels and 52.6% in dried ripe kernels. Polyunsaturated FAs represented by L (C18:2) and Ln (C18:3) acids accounted for 36.6% in unripe kernels, 33.4% in ripe kernels and 33.4% in dried ripe kernels. During seed maturation, the content of polyunsaturated FAs declined in favor of oleic acid, desaturase activity became lower in ripe seeds, permitting the accumulation of its substrate (C18:1) into the TGs. The content of C18:2 and C18:3 declined during seed development, indicating a decrease of photosynthetic activity in ripe seeds because C18:3 is the major FA of photosynthetic biomembranes.