Study On Lipase-catalyzed Acidolysis Of Alcohol-soluble Soybean Phospholipids With Palmitic Acid

Soybean phospholipids is a natural surfactant, with emulsification, dispersion, foaming, releasability, lower viscosity, water retention and other functions. But it contains a number of unsaturated double bonds, which is easy to suffer from oxidation when exposures to oxygen, forming volatile aldehydes, ketones and other small molecules, and resulting in deeper color. The instability of soybean phospholipids largely restricts its application. To increasing its oxidative stability, immobilized lipase-catalyzed acidolysis of soybean phospholipids with saturated fatty acids was carried out in organic media which could introduce more saturated fatty acid, and no trans fatty acids were produced simultaneously.The immobilized lipases and reaction media were selected with alcohol-soluble soybean phospholipids as raw materials and palmitic acid as acyl donor. Finally, hexane and Lipozyme TLIM were chose as reaction solvent and catalyst respectively.According to the single factor and response surface methodology, the optimum conditions was as follow: the substrate ratio (palmitic acid/phospholipids) 1.804:1(g/g), the concentration of phospholipids (phospholipids/hexane) 0.2g/mL, lipase dosage (based on total substrates) 21.95%, reaction temperature 63.45℃, reaction time 49.44h, water addition (water/hexane) 2μL/mL, under the optimum conditions the content of palmitic acid in phospholipids was 34.64%.The nature of different phospholipids also affected the incorporation of palmitic acid in lipase-catalyzed acidolysis. The selectivity of Lipozyme TLIM in lipase-catalyzed acidolysis for phosphatidylcholine and phosphatidylethanolamine was analysised, and the following order of reactivity was observed: phosphatidylcholine > phosphatidylethanolamine.The physical and chemical properties and the composition of fatty acids in raw soybean phospholipids and enzymatically modified phospholipids were determined, which showed that Iodine Value was reduced from 95.5g/100g to 68.7g/100g, and neither of them contained trans fatty acids. The HLB value were 5.1 and 6.5 respectively, indicating enzymatically modified phospholipids was more hydrophilic.The oxidative stability was tested by Schaal oven storage stability test, which showed that the POV and IV of enzymatically modified phospholipids were more stable than raw soybean phospholipids, indicating the oxidative stability had been improved.