| The distribution position of fatty acids in the triglyceride framework affects the absorption to human body. By the enzymatic modification of triglyceride, the change of structure and composition can get more suitable products for human nutritional requirement. Human milk fat substitute (HMFS) is one of enzymatic modification products. Human milk fat (HMF) becomes the gold standard, which facilitate the healthy growth of infants, because the special structure characteristics of HMF. Such as70%of fatty acids at the Sn-2position of triglyceride are palmitic acid. Which can hydrolysate with bile salt can form chylomicron and can be absorbed by human body easily. Lard also has the same structure characteristics. So the lard can be modified to form HMFS, in order to make up the phenomenon of the increasingly lack of human milk, and further enhance the development and use value of lard as a major resource.Using Sn-1,3specificity lipase as catalyst, acidolysis reaction of lard and mixed fatty acid in solvent-free medium were investigated. Triglyceride structure, fatty acids constitute and content of modified lard can resemble those of human milk fat. Through retaining the structure which most of fatty acid are palmitic acid at Sn-2position of triglyceride, adjusting the fatty acid (lauric acid and stearic acid) content at Sn-1,3position of triglyceride.Corn germ oil and soybean oil are rich in unsaturated fatty acid but poor in stearic acid. Coconut oil has the highest levels of lauric acid. The three kinds of vegetable oil were mixed to prepare free fatty acid as acyl donor. The optimal quality ratio for coconut oil:corn germ oil: soybean oil0.2:0.3:0.5. Lipase is the key factor of the enzymatic reaction. Through the three Sn-1,3specificity lipase screening, Lipozyme TL IM was determined to catalyze the enzymatic acidolysis reaction. And Lipozyme TL IM as acidolysis reaction catalyst can not be reused more than five times in batch reaction.The influences of the reaction temperature, the enzyme load, stirring rate, the mass ratio of substrates, reaction time and water activity on acidolysis reaction in solvent-free medium were investigated systematically. When the initial water activity was controlled0.57, the total C12:0, C18:0content and C16:0content at the Sn-2position of the product were5.76%,8.93%and63.47%respectively. And the fatty acid composition and distribution were similar with HMF using1:2.5mass ratio of lard to mixed fatty acid catalyzed by10%(W/W) enzyme to substrate at65℃under the rotation speed of220r/min for10h.The purification methods of triglyceride of product were studied further. The feasibility analysis of urea adduction method and solvent extraction method to separating and purifying triglycerides were compared. The method of solvent extraction was more suitable for the separation and purification of the product than that of urea bag. The effects of extraction agent concentration, feed liquid ratio, extraction temperature and extraction rate on the influence of the purification degree were determined. The optimum conditions were showed as follows: using solvent extraction methods, with85%ethanol as extracting agent, coarse sample: extraction agent (w/v)=1:3, at room temperature and three times extraction. And through the column of alumina, the acid value of purification material was2.2mgKOH/g, which proved that fatty acid was almost removed completely. And the physical and chemical properties of triglyceride of product and lard were determined and compared. The results indicated acid value and melting point reduced, iodine value and saponification value increased in triglyceride of product. |
PDF Full Text Request