Changes in main components of raw and roasted peanut and sesame seeds I Oil properties, fatty acid composition, hydrocarbons and sterol constituents

ABSTRACT

The physical and chemical properties of oils of peanut and sesame seeds that were roasted at 100, 120, 140 and 160°C for two hours were studied. The refractive index increased while acid value and unsaponifiable matter decreased. Iodine value showed a slight fluctuation. Peroxide value increased to a higher value at 120°C in the case of peanut seeds and at 140°C for the sesame seeds then it decreased when the seeds were heated at higher temperatures. As the roasting temperatures increased, the total saturated fatty acids increased while total unsaturated fatty acids decreased in both seed oils. Palmitic acid, which represents the major saturated fatty acids in peanut and sesame seed oils showed a slight increase, while oleic acid decreased with increasing roasting temperatures. Generally, roasting process caused noticeable changes in the fatty acids composition of peanut and sesame oils. The hydrocarbon compounds of the unsaponifiable matter separated from peanut seed oil showed remarkable changes when peanut seeds were subjected to different roasting temperatures. Delete B-sit sitosterol was the major sterol compound in this fraction which decreased with the increase of roosting temperatures. In the case of sesame seed oil, squalene, which represents the main hydrocarbon compound in the hydrocarbon fraction suffered severe and drastic changes when sesame seeds were resorted at 100C-160°C- while an unknown sterol compound [1] with R.R.T. 1.51 was the major sterol compound in sesame oil followed by B-sit sterol. Also, drastic changes were not iced in sterol compounds when sesame seeds were roasted at 100C-160°C