Combinatorial effects of longan ( Dimocarpus longan ) peel extract and lecithin on stability of soybean oil and the oxidative stability of fried shrimp crackers during storage

Soybean oil contains relatively high polyunsaturated fatty acids (PUFAs) which present problems for storage, as they are not oxidatively stable. To solve this problem, the present study mixed a naturally hydrophilic antioxidant (longan peel extract, LP) with an amphiphilic compound (lecithin) to create a water-oil based interface with antioxidant properties and analyzed the effect on lipid oxidation. Pretreatments with LP, lecithin, and a combined mixture of LP and lecithin improved oxidative stability in refined soybean oil heated at 70 and 180 degrees C, by decreasing the resulting peroxide value (POV), conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS). Pretreatment with a combination of both LP and lecithin exhibited a synergistic effect in lowering TBARS and maintaining alpha-tocopherol, which is an endogenous antioxidant in soybean oil. The pretreatment helped to maintain PUFAs, which led to the prevention of POV, CD and TBARS formation in the oil. In deep-frying experiment, application of LP, lecithin, and a combined mixture of the two, improved the stability of the frying oil in addition to fried shrimp crackers that were cooked in the oil. Collectively, the results demonstrated the potential of LP, lecithin, and their combination in improving oxidative stability of vegetable oils under high-temperature conditions.