Preparation Of Breast Milk Fat From Tibet Yak Ghee-based Substitute

The Tibet yak ghee was choose as substrate to produce human milk fat substitutes (HMFS) by physical mixing and enzymatic transesterification. Both two product were evaluated by a model which was compared with commercial infant formula milk fat, where the reaction of enzymatic trnasesterification was optimized. Main research contents and results of this paper were shown as follows:1. The fattty acid composition and positional distribution of Tibet yak ghee was detected similar to human milk fat but the oleic acid and linoleic acid was somehow lower, so Tibet yak ghee was blanded with OPO structured lipid and rice bran oil to obtained the HMFS using the Lingo model.2. The enzymatic transesterification was catalyzed by immobilized lipase RM IM to obtain HFMS. The reaction was optimized with considering a limited acyl migration and a more similar fatty acid compositio to human milk fat. The results showed that within free fatty acid and fatty acid esters these two type acyl donors, low degree of acyl migration can be found when fatty acid ester was used. Then other factors of water activity, sunstrates ratio, reaction time and temperature was optimized by response surface methodology. The optimum reaction conditions were obtained:reaction time,5.7 h; temperature,68 ?; substrate molar ratio, Tibet yak ghee:sunflower oil ethyl ester:oleic ethyl ester= 2.13:1:1(mol/mol/mol); enzyme water activity,0.61; enzyme dosage,10 wt%. In the structured lipids, the content of total linoleic acid and palmitic acid sn-2 of final product in model validation actually were 17.59% and 56.40%, which is in consistent with the predicted value. The final synthesized product was similar to human milk fat structure, which made it possible to be utilized for infant formula as breast milk fat substitute.3. An evaluation model with several indicators were used to score the similarity of two ways of synthetic human milk fat substitute. Through both of them were short on the aspect of total fatty acids, sn-2 fatty acids, polyunsaturated fatty acids. But, we can get the conclusion that the structure lipid synthesized by enzymatic transesterification were much more better on account of the substrate has a better property which can be modified in the process. The score of similarity evaluation on total fatty acids, sn-2 fatty acids, polyunsaturated fatty acids were 93.8%,87.4%, 95.3%, respectively. The desired product can be achieved by the use of response surface optimization of experimental conditions. Additionally, it can be concluded from the accelerated oxidation experiment is that, comparing with the structure lipid, the oxidation stability of blended fat is higher and much more better for preservation and storage.