Comparison of chemical characterises of crude and refined edible vegetable oils

摘要

The present study was undertaken to compare the chemical characterises of crude and refined edible vegetable oils viz. cotton, flaxseed, groundnut, soybean and mustard. The seeds were collected from farmer's field at Hisar, Haryana and grounded to powder. Oil was extracted by Soxhlet method using petroleum ether (60-80°C) for 8 h. Solvent extraction processes include basically three steps: preparation, extraction, and desolventizing. Refining of oils was done by chemical method in different steps: degumming, neutralization, bleaching and deodorizing. Samples were studied for oxidative quality indices viz. free fatty acid, peroxide value, p-anisidine value, total oxidation value, conjugated dienes, carotenoid, total tocopherol, thiobarbituric acid value and fatty acid composition. Free fatty acid ranged from 0.9 to 3.49 (% as oleic acid) for crude oils and from 0.3 to 1.98 (% as oleic acid) for refined oils. Peroxide value ranged from 1.26 to 3.4 (meq/kg) for crude oils and for refined oil range was 0.92 to 1.5 (meq/kg). p-Anisidine value ranged from 1.75 to 10.14 and 1.03 to 4.77 for crude and refined oils respectively. Total oxidation values ranged from 6.41 to 16.94 and 3.36 to 6.74 respectively for crude and refined oils. Conjugated dienes ranged from 0.36 to 3 (% as dienoic acid) for crude oils and 0.21 to 3.2 (% as dienoic acid) for refined oils. The range of carotenoid was 41.3 to 126.09 (mg/kg) for crude oils and 30.2 to 75.69 (mg/kg) for refined oils. Total tocopherol value ranged from 476 to 1620 (mg/kg) and 219 to 829 (mg/kg) for crude and refined oil respectively. Thiobarbituric acid ranged from 4.63 to 15 (meq/kg) for crude oils and for refined oils it was 2.73 to 9.3 (meq/kg).