Lipid components and oxidative status of selected specialty oils

Abstract

Many vegetable oils are marketed as specialty oils because of their retained flavors, tastes and distinct characteristics. Specialty oil samples which were commercially produced and retailed were purchased from local superstores in Reading, UK, and Uppsala, Sweden and profiled for detailed lipid composition and oxidative status. These oil samples include: almond, hazelnut, walnut, macadamia nut, argan, avocado, grape seed, roasted sesame, rice bran, cold pressed, organic and cold pressed, warm pressed and refined rapeseed oils. The levels of PV were quite low (0.5-1.3mEq O₂/kg) but AV and Rancimat values at 100 °C (except for rapeseed oils) varied considerably at (0.5-15.5) and (4.2-37.0 h) respectively. Macadamia nut oil was found to be the most stable oil followed by argan oil, while walnut oil was the least stable. Among the specialty oils, macadamia nut oil had the lowest (4%) and walnut oil had the highest (71%) level of total PUFA. The organic cold pressed rapeseed oil had considerably lower PUFA (27%) compared with other rapeseed oils (28- 35%). In all the samples, α- and γ- tocopherols were the major tocopherols; nut oils had generally lower levels. Total sterols ranged from 889 to 15,106 μg/g oil. The major sterols were β-sitosterol (61-85%) and campesterol (6-20%). Argan oil contained schottenol (35%) and spinasterol (32%). Compared with literature values, no marked differences were observed among the differently processed, organically grown or cold pressed rapeseed oils and other specialty oils in this study.