Effect of chemical refining on Citrullus colocynthis and Pongamia pinnata seed oil

Bio -diesel production from conventional vegetable oils (soybean, sunflower, safflower, palm and rapeseed) has progressively stressed food uses, price, production and availability of these oils. Consequently, this has ignited the search for additional/ non- conventional, regional oil yielding raw materials to fulfill the increasing demand of oil for edible and bio- fuel production. Citrullus colocynthis and Pongamia pinnata (underutilized plants) oil was found to have good economical values. But crude oil obtained from natural resources contains a lot of impurities which should be removed before its use. Chemical refining involves degumming, alkali refining and bleaching are aimed to remove impurities like free fatty acids, phosphatides, metal ions, oxidation products and waxes. Oil from the both plant seeds was evaluated (both before and after refining) for different physico-chemical parameters like free fatty acids, iodine value, peroxide value, saponification value, unsaponifiable matter and fatty acid composition. Oil yield (30 -35 %) in both plants was found average. After refining, per cent reduction of free fatty acid value by (62.79 and 63.9), iodine value (25.59 and 27.37), saponification value (13.46 and 13.43), peroxide value (65.76 and 59.64) was observed in C. colocynthis and P. pinnata oil , which is helpful in increasing the oxidative stability and susceptibility towards trans -esterification. Unsaponifiabl e matter in C. colocynthis and P. pinnata was reduced by 54.78 and 49.78 per cent which is helpful in decreasing the amount of secondary metabolites and increasing the purity of oils. Analysis of C. colocynthis and P. pinnata oil show s that it was composed mainly of palmitic, stearic, oleic, linoleic and linolenic esters. After refining, saturated fatty acids were found reduced from 23.56 to 19.17 and 18.75 to 15.78 per cent and total unsaturated fat ty acids were found to increase from 74.68 to 78.39 and 71.56 to 78.77 in both oils. It makes oil favorable for edible purposes as it can reduce plasma tri glycerides.