Study On Preparation Of High Purity Lecithin From Duck Egg Yolk

Lecithin, a sort of natural phospholipids, is one of the basic substances in life activities, and it exists in almost all living organisms. It has been widely used in food processing, nutrition and health care, pharmaceutical, cosmetics and other fields due to its excellent emulsifying properties and high nutritional value. Duck egg yolk is rich in lecithin, accounting for about8%to10%by weight of the duck eggs, which is about0.5%higher than eggs. Therefore, study on the preparation of high purity lecithin from duck egg yolk has sound economic values and wide industrial application prospects. With fresh duck egg yolk as raw material, enzymatic hydrolysis method and low-temperature precipitation method were taken to extract egg yolk lecithin based on ethanol solvent extraction technique, and the extraction process was optimized respectively. Ultimately, the low-temperature precipitation method was determined as ideal extraction method, which was applied to the scale-up experiment. The main conclusions are as follows:(1) The egg yolk lecithin extraction process was investigated by protease hydrolysis extraction optimization, with lecithin yield and total phospholipid content as evaluating criterion. During the extraction process, single factor and orthogonal experiments were studied to obtain optimizing conditions. The results showed the optimum extraction conditions were:the neutral protease dosage0.1g/100g yolk, egg yolk-ethanol ratio1:4.5, extraction temperature35℃, extraction time30min and extracting three times. Under these optimized conditions, the lecithin yield and phospholipid content were9.30%and80.86%, respectively. Furthermore, the HPLC detection indicated that the extracted lecithin had65.81%of phosphotidylcholine and14.68%of phosphotidylethanolamine.(2) During the low-temperature precipitation extraction process, The optimal extraction conditions were the egg yolk-ethanol ratio was1:4.5, extraction temperature was35℃, extraction time was30min, extractiing three times, hexane-acetone volume ratio was1:2.5and frozen temperature of-20℃, respectively,determined by single factors and orthogonal experiments. Under these conditions, the lecithin yield and phospholipid content were9.37%and97.68%, respectively, while the HPLC detection showed that the yolk lecithin had77.42%of phosphotidylcholine and18.47%of phosphotidylethanolamine.(3) By comparision, the main components of lecithin extracted by two methods were both PC and PE, with close yield, but higher purity lecithin was obtained by the low-temperature precipitation method. The scale-up experimental results of low-temperature precipitation were as follows:lecithin yield9.20%, phospholipid content94.75%, the HPLC quantitative detection indicated that the final lecithin product had75.82%of phosphotidylcholine and17.55%of phosphotidylethanolamine, respectively.To sum up, the experiment results show that the selected extraction method is feasible in process and simple in operation, which provides a foundation for duck egg yolk lecithin industrialization.