Preparation And Evaluation Of Human Milk Hat Substitutes

Human milk fat (HMF) is one of the important nutrients in human milk. The uniquestructure of HMF, i.e., palmitic acid is mainly located at the sn2position of thetriacylglycerol backbone, is important for the absorption of fats and some minerals in infants.However, there is an inadequacy of breastfeeding or lack of feeding conditions greatly due tothe personal, domestic and social factors. According to World Health Organization statistics in2005, the rate of exclusive breastfeeding is less than50%for infants within6months in China.Thus, at the proposal of breastfeeding, increase of infant formula for diet is a good choice tomeet the growth and development needs of infants. Fatty acid composition of fat in thetraditional infant formula is close to that of human milk fat, but the fat structure issignificantly different from HMF’s, fatty acids and the absorption of mineral elements had anegative impact, which played negative roles in the absorption of fats and some minerals.With the contradiction of the demand and supply of the growing high quality infant formula,human milk fat substitutes (HMFS) as an important ingredient in the preparation of infantformula will be salable in China. Until now，Netherlands Unilever and Israel AAK are theonly two companies to provide human milk fat substitute products, and one of the mosttypical products is BetapolTMfrom Unilever. In2008, OPO type HMFS is allowed to add toinfant formula, which is approved by the Chinese Ministry of Health. With the deepimplementation of the Food Safety Law and relevant national standards of infant formula,market demand of HMFS will be increased in future.The study firstly fatty acid composition and distribution of HMF, from mothers overdifferent lactating periods in Guangzhou, China, were analyzed. The results showed that thecontent of oleic and palmitic acids in mature milk are36.96%and20.22%, respectively. Themain structure of HMF is1,3dioleoyl2palmitylglycerol. Based on the composition of thetotal and sn2fatty acids of mature milk fat, an efficient evaluation model was innovativelyestablished by adopting the “deducting score” principle. The model showed good agreementbetween the scores and the degree of similarity by assessing15samples from differentsources. Four samples of HMF got the highest score (G≥98.69), which referred to the highest degree of similarity, five samples of Infant formula had a lower degree of similarity (G=49.28–78.18).While corn oil and soybean oil had the least parallel with HMFS compared withother samples (G=26.20and30.01, respectively). The established evaluation model is simpleto evaluate the similarity of samples from different region and samples between HMF andHMFS.On the basis of the study of fatty acid composition and distribution of fat (n=11) fromfour different parts of pigs, inexpensive leaf lard was selected as raw material.34L leaf lardwith a low melting point obtained by dry fractionation of leaf lard was used as substrate foracidolysis catalyzed by Lipozyme RM IM. The OPO type human milk fat substitutes weresuccessfully produced under the optimal conditions: a substrate molar ratio of4:1(camelliaoil fatty acids/34L lard),6%(w/w) of enzyme loading, and6h of reaction time at45oC.Under the optimal parameters mentioned above, the incorporation of oleic acid was up to50%and the level of acyl migration was low (～1.25%). On the basis of gas chromatographydetermination and “deducting score” principle, a model was properly established forcharacterizing the quality of triacylglycerols enriched with1,3dioleoyl2palmitoylglycerol(OPO). This approach would be a valuable contribution in structured lipids industries becauseonly gas chromatography determination was involved.The reusability of Lipozyme RM IM was investigated, and the results showed that14batches were tested under the optimal conditions for the production of OPO type human milkfat substitutes. The scale up experiment, about40folds, of producing OPO type human milkfat substitutes were performed to verify the feasibility of the whole process at a larger scale.Furthermore, molecular distillation was employed for purification of OPO type human milkfat substitutes. The effect of evaporation temperature was investigated on the purity and theLovibond color of OPO type human milk fat substitutes. The optimal evaporation temperaturewas achieved at180oC. Purified OPO type human milk fat substitutes with a purity of91.39%and a Lovobond color of yellow and red values of8.8and6.0were acquired. Theacid value and peroxide value were not detected. The study of storage stability of purifiedOPO type human milk fat substitutes was carried out, and the results showed that the stabilityof the product was improved by adding natural antioxidant VE.To provide useful information for studies on the synthesis of human milk fat substitutes by lipase catalyzed acidolysis. Tripalmitin enriched triacylglycerols were reacted with amixture of equimolar quantities of fatty acids (C8:0C18:3n3). The chain length selectivityof five lipases was determined. The effects of the molar ratio, temperature and time onincorporation were also investigated. Novozym435acted strongly on C12:0and C14:0. ForPPL catalyzed acidolysis, incorporation degrees for C8:0, C10:0, and C12:0were foundmarkedly higher. For Lipozyme TL IM and Lipozyme RM IM, incorporation degrees forC12:0, C14:0, C18:1n9and C18:2n6were found higher. Lipase PS IM catalyzed weakly onC8:0and C18:3n3. On the basis of significantly different levels of acyl migration to the sn2position, lipases were in the order of lipase PS IM <Lipozyme TL IM <Lipozyme RM IM.MLM type triacylglycerols are very important ingredients for premature infant growthand mature of their brain. The typoselectivity of crude CBD T1lipase was firstly studied in amulti competitive acidolysis reaction. Besides, the possibility of using the lipase to synthesizeMLM type structure lipids was investigated. The crude CBD T1lipase discriminated stronglyagainst C18:1n9(α=0.23) and showed the highest preference for C8:0(α=1), followed byC10:0(α=0.83). A structural model was constructed to briefly explore interactions betweenthe lipase and its substrate. The optimum conditions were a molar ratio of3:1(C8:0/soybeanoil) in3mL hexane at a temperature of50°C, and a reaction time of48h in the presence ofcrude CBD T1lipase (20%, w/w substrates) and water content (7.5%, w/w enzyme). Underthese conditions, the incorporation of C8:0was29.59%, and the purity of MML and MLL inacidolysis products was70.51%, indicating that the use of the lipase in the modification offats and oils was possible.