Lipid class compositions, tocopherols and sterols of tree nut oils extracted with different solvents

The chemical compositions of tree nut oils were examined. The oils of almonds, Brazil nuts, hazelnuts, pecans, pine nuts, pistachios and walnuts were extracted using hexane and chloroform/methanol. The chloroform/methanol system afforded a higher oil yield for each tree nut type examined (pine nuts had the highest oil content while almonds had the lowest). The lipid class compositions of the tree nut oils were analyzed using the thin-layer chromatography-flame ionization detector and showed that triacylglycerols were the predominant lipid class present. Smaller amounts of sterols, sterol esters, phospholipids and sphingolipids were also present. The fatty acid compositions of the tree nut oils were analyzed using gas chromatography, showing that oleic acid was the predominant fatty acid in all samples except pine nut and walnut oils, which contained high amounts of linoleic acid. The sterol and stanol content and compositions were analyzed using gas chromatography; beta-sitosterol was the predominant sterol present in all samples, with lower amounts of campesterol, stigmasterol, Delta 5-avenasterol, 22-nordehydrocholesterol, 24-methylenecholesterol, cholesterol, cholestanol and beta-sitostanol also present. The tocopherol compositions were analyzed using high-performance liquid chromatography, showing that alpha- and gamma-tocopherols were the predominant tocopherol homologs present; however, delta- and beta-tocopherols were also detected in some samples.