Preparation And Evaluation Of High Similarity Human Milk Fat Substitutes

Human milk is the most ideal food for infants.Human milk fat provides 40%?50%of energy,essential fatty acids and fat-soluble vitamins for infants,which is of great importance for the growth and development of infants.Infant formulas are the best alternative when breastfeeding is not available.The proportion of fat in infant formula is about 20%?30%,which is called human milk fat substitute.At present,the composition of human milk fat substitute is quite different from that of Chinese milk fat.These differences are mainly reflected in the lack of sn-2 palmitoyl triglycerides and lauroyl triglycerides.In this paper,the natural oil rich in sn-2 palmitoyl triglycerides was screened and modified by fractionation,transesterification and physical blending to prepare a human milk fat substitute product with high similarity to Chinese milk fat composition.The main research contents are as follows.Firstly,the lipid composition of six fish oils which may be rich in sn-2 palmitoyl triglycerides was analyzed by gas chromatography and reverse phase high performance liquid chromatography(RP-HPLC).The results showed that fish oil E and F were rich in sn-2palmitoyl triglycerides.In fish oil F,the contents of palmitic acid,oleic acid and linoleic acid were 24.27%,33.90%and 21.48%,respectively.The content of sn-2 palmitic acid was 48.01%(65.95%of total palmitic acid was distributed in sn-2 position).The sn-2 palmitoyl triglycerides were mainly composed of 1-oleoyl-2-palmitoyl-3-linoleoylglycerol(OPL)and 1,3-dioleoyl-2-palmitoylglycerol(OPO),with the contents of 31.43%and 19.49%respectively.The contents of sn-2 palmitic acid and sn-2 palmitoyl triglycerides in fish oil F were close to those in human milk fat,which has not been reported in other natural oils.Therefore,fish oil F has the potential to be used as the base oil for the preparation of high similarity human milk fat substitute.Secondly,the solvent fractionation was used to enrich OPL and OPO in fish oil F,and the conditions of solvent fractionation were optimized.When the ratio of fish oil F to acetone was1:8(w/v),the temperature of solvent fractionation was-30? and time was 16 h,the total palmitic acid,oleic acid and linoleic acid content in fractionated fish oil F were 28.27%,29.41%and 20.28%respectively.The content of sn-2 palmitic acid was 50.62%.By calculation,the content of sn-2 palmitic acid relative to total palmitic acid was 59.68%.The contents of OPL and OPO in fractionated oil were 34.64%and 26.66%respectively by RP-HPLC.The total content of OPL and OPO was 20.38%higher than that of crude oil.Further,the composition of triglycerides in fractionated fish oil F was determined by UPC²-Q-TOF-MS.Thirty-six kinds of triglycerides were detected,among which the contents of OPL and OPO were 17.45%and13.90%,respectively.Fractionated fish oil F can be used as an excellent source of sn-2palmitoyl triglycerides.Thirdly,fish oil F and coconut oil were used as raw material to synthesize lauroyl triglycerides by enzymatic method,and the conditions of enzymatic synthesis were optimized.When the conditions were solvent-free system,fish oil F to coconut oil molar ratio of 0.8:1,NS40086 lipase dosage of 22.0 IUN/g,reaction temperature of 65?,reaction time of 8 h,the content of lauroyl triglycerides in the final product was 67.01%.The product was purified by molecular distillation.The contents of diacylglycerol and free fatty acid were 3.09%and 1.17%respectively,and the content of lauroyl triglycerides increased to 76.89%.The triglyceride composition of the purified product was analyzed by UPC²-Q-TOF-MS.The lauroyl triglycerides with high content in the purified product were LLaLa,OLaCa,LaLaM,LLaL,OLaLa,PLaLa,OPLa,OLaL,LPLa,OLaO and OMLa(Ca,decanoic acid;La,lauric acid;M myristic acid;P,palmitic acid;O,oleic acid;L,linoleic acid),covering the lauroyl triglycerides with high content in human milk fat.The synthetic product can be used as an excellent source of lauroyl triglycerides.Finally,seven kinds of natural oils and two kinds of modified oils mentioned above were selected as base oils.Based on the composition characteristics of Chinese milk fat,the physical blending model of human milk fat substitute was established to prepare high similarity human milk fat substitute.When the ratio was sunflower seed oil:rapeseed oil:corn oil:soybean oil:palm oil:palm olein:lauroyl triglycerides:fish oil E:fractionated fish oil F=5.07%:0.06%:0.29%:5.47%:0.10%:0.10%:21.00%:51.34%:16.57%,the human milk fat substitute A was prepared.G_FA,G_sn-2,G_TAG and G were 98.83,84.95,87.04 and 90.27,respectively.After removing four kinds of low content vegetable oil,human milk fat substitute B was prepared.The ratio was sunflower seed oil:soybean oil:lauroyl triglycerides:fish oil F:fractionated fish oil F=4.93%:5.90%:21.00%:51.60%:16.57%,and G_FA,G_sn-2,G_TAG and G were 98.80,85.03,87.07 and 90.30,respectively.The human milk fat substitute A and B were highly similar to human milk fat.In conclusion,fish oil F was selected as a new oil source rich in sn-2 palmitoyl triglycerides.Using fish oil F as raw material,human milk fat substitute with high similarity to Chinese milk fat was prepared by solvent extraction,enzymatic transesterification and physical blending.This high similarity human milk fat substitute provides a new choice for infant formulas,which is of great significance to improve the quality of infant formulas in the Chinese market.