Studies on cashew (Anacardium occidentale) nut oil

The oils from two varieties of cashew nuts (Anacardium occidentale L.) were analyzed for physical and chemical properties. Oil content ranged from 42.91-43.28% (dry basis). Except for unsaponifiable matter content (4.96-5.76 and 0.78-1.45% for Tabinga and Makiling variety, respectively) and peroxide value (0.54-0.68 and 1.55-2.80 for Tabinga and Makiling variety, respectively), small varietal differences were observed in physical and chemical properties. The specific gravity ranged from 0.8532-0.9095 while refractive index ranged from 1.4451-1.4574. Saponification values of 183-190 and iodine values of 65.2-78.8 indicated that cashew nut oil consists of long chain fatty acids and had a moderate degree of unsaturation, respectively. Free fatty acid values of 1.08-5.80 and peroxide value of 0.54-2.80 suggested that the oil had undergone early stages of hydrolysis and oxidation. The oils from one year stored nuts had a lower iodine value and higher free fatty acid number than newly harvested nuts. Major fatty acids were oleic (61.92-63.93%), linoleic (16.67-20.52%), palmitic (10.25-10.72%) and stearic acid (4.73-9.01%). Small amounts of palmitoleic (0.16-0.31%) and traces of linoleic acid were also detected. Linoleic acid content of the oil decreased after one year storage of the nuts. Storage stability study revealed the least deterioration in hydrolytic and oxidative rancidity in oils stored at 5 deg C under nitrogen gas. Variation in storage temperature (from room T to 5 deg C) caused no significant changes in peroxide and iodine values. Free fatty acid and saponification number from oils under air were not significantly different from those of oils stored under nitrogen at room temperature but significantly different for oils stored at 5 deg C. Treatment with nitrogen gas must be coupled with lowering of storage temperature for effective inhibition of hydrolytic rancidity.