The Composition,Similarity Evaluation And Preparation Of Human Milk Fat Substitutes

Human milk is the best food for infants.Human milk fat?HMF?has special composition and structure.HMF provides 40%⁵0%of energy for infants,and also provides essential fatty acids and fat-soluble vitamins,which has an important effect on the growth and development for infants.When it is impossible to breast-feed for many reasons,commercial formula is the best alternative,the fat of which belong to human milk fat substitutes?HMFS?.The ultimate aim of HMFS is to simulate the composition and structure of HMF as far as possible.Natural oils are mainly composed of triacylglycerols?TAGs?.At present,the studies on formula fat have mainly focused on the fatty acid composition,but TAG stucture was not paid much attention.The similarities between formula fats and HMF are also not clear.There are still significant differences in TAG stucture between formula fats and HMF.This study systematically analyzed and compared the compositions of commercial formula fats and HMF.Then,a multi-index classification evaluation system of HMFS was established with the parameter of similarity coefficient,and the similarities of commercial formula fats to HMF were analyzed by this evaluation system.At last,HMFS with high similarity was prepared based on TAG composition.The main results were as follows:Firstly,180 representative commercial formulas were selected.According to the fat sources,the formula fats were divided into plant-oil formula fat?POF?,cow's milk/plant-oil formula fat?CPF?and goat's milk/plant-oil formula fat?GPF?.The compositional analysis of three types of formula fats showed that there were signicant differences in fatty acid and sn-2fatty acid composition between POF and CPF/GPF.POF had higher levels of oleic acid?OA?and sn-2 OA,while CPF and GPF had higher levels of short-chain saturated fatty acids,palmitic acid?PA?,C18:0,trans fatty acids and sn-2 saturated fatty acids?except C12:0?.The proportion of relative PA at the sn-2 position in CPF was significantly higher than that of POF.With regard to TAG species,there were significant differences among three types of formula fats.POF contained higher proportions of OOO,while CPF and GPF contained higher proportions of TAGs with short-chain/medium-chain saturated fatty acids?SC/MC-SFAs?.The compositional analysis of commercial formulas with three stages?including infant formula,follow-on formula and growing-up formula?revealed that there was little difference among them for POF and CPF,whereas infant formula from GPF had higher levels of OA,LA,linolenic acid?LNA?,sn-2 OA and sn-2 LA,and also had lower levels of SFAs,trans fatty acids,sn-2 SFAs and TAGs with SC/MC-SFAs.In brief,there were obvious differences between POF and CPF/GPF,and the differences between CPF and GPF were relatively small;no differences was found among formulas with three stages in POF and CPF,whereas there were significant differences between infant formula and follow-on/growing-up formula in GPF.Then,chemical composition of the selected 180 formula fats were compared with those of 309 HMFs with different lactation stages from Wuxi analyzed in previous study of our laboratory.The results indicated that formula fats contained higher levels of C4:0^C8:0 and LNA,and lower levels of long-chain polyunsaturated fatty acids?LC-PUFA?than those of HMFs.In terms of sn-2 fatty acid composition,the proportions of relative OA,LA and LNA at the sn-2 position in formula fats were higher than those of HMFs,whereas the proportions of relative PA and LC-PUFAs were lower.In addition,there were significant differences in TAG species between formula fats and HMFs.Formula fats had higher levels of OOO and TAGs with SC/MC-SFAs.There were significant differences in OPL and OPO between formula fats and HMFs.Formula fats were also lack of many kinds of TAGs rich in HMFs.Although some formulas has decreased the differences with HMFs in TAG composition by adding OPO,the proportions of relative PA at the sn-2 position in these formulas were much lower than that in HMFs.These results indicated that formula need the supplementation of not only OPO,but also other TAGs containg PA mainly at the sn-2 position?such as OPL?.In general,commercial formula fats were similar to HMF in major fatty acid composition,but there were significant differences in micro fatty acid,sn-2 fatty acid and TAG composition between formula fats and HMF.Next,a multi-index classification evaluation system of HMFS was established with the parameter of similarity coefficient,and 17 oils with representative chemical composition were selected and applied to this evaluation system.The results showed that the similarity coefficients could reflect the differences in chemical composition between these oils and HMF,which indicated the validity of the evaluation system.The evaluation system can not only rapidly evaluate the similarity of HMFS to HMF,but also provide information for the development of HMFS.The similarities of 180 commercial formula fats were evaluated by the evaluation system baesd on the composition of 309 HMFs from Wuxi analyzed in previous study of our laboratory.The results showed that in terms of third-level indexes,the similarity coefficients in major fatty acids(G_MAFA)of 76.67%of formulas were more than 80.The similarity coefficients in micro fatty acids and sn-2 major fatty acids(G_{sn-2 MAFA})of 12.78%and 32.22%of formulas reached 60,whereas the similarity coefficients in sn-2 micro fatty acids,major TAGs(G_MATAG)and micro TAGs of all formulas were below 60.In terms of second-level indexes,the similarity coefficients in fatty acids of 57.22%of formulas reached60,whereas the similarity coefficients in sn-2 fatty acids(G_{sn-2 FA})and TAGs(G_TAG)of all formulas were below 60.Relatively speaking,the G_{sn-2 FA}n-2 FA of CPF and GPF were higher than that of POF,and the G_TAGAG of GPF was higher than those of POF and CPF.In terms of first-level index,the total similarity coefficients?G?of all formulas were lower than 60,82.78%of which was 20⁵0.The G of GPF was higher than those of POF and CPF.Therefore,the evaluation system can directly find that commercial formula fats only had high similarities in fatty acid composition,and more attention should be paid to TAG structure.Finally,19 kinds of oils were selected as base oils,and physical blending model of HMFS was established based on TAG composition of HMF.The similarities of HMFSs were evaluated by the evaluation system.The results showed that the main reason of loss was lack of OPL.Palm stearin was selected as material to obtain the high purity of PPP.PPP,OA and LA were used as substrates for acidolysis catalyzed by Lipozyme RM IM to prepare OPL-enriched structured lipid.After optimization,the optimized conditions were obtained as substrate molar ratio?PPP/OA/LA?as 1:4:5,enzyme load as 12%,temperature as 55°C,reaction time as 6 h.The sn-2 PA,%sn-2 PA,%sn-1,3 OA and%sn-1,3 LA in the final production were 70.15%,61.81%,34.85%and 41.98%,respectively.The OPL and POO contents were 42.55%and 9.64%.Physical blending was developed with 19 kinds of oils and OPL-enriched structured lipid.Then three kinds of HMFSs were obtained,including HMFS_G2,HMFS_C2 and HMFS_P2,which were assessed by the evaluation system.The G_MATAG,G_MAFA,G_{sn-2 FA}n-2 FA and G of HMFS_G2 were 89.20,81.30,80.07 and 83.52,respectively,which could considered as a HMFS with high similarity.The G_MATAG and G_MAFA of HMFS_C2were 89.09 and 81.26,but G_{sn-2 FA} was only 70.31,and G was 80.22.HMFS_C2 could be regarded as a good HMFS.All similarity coefficients of HMFS_P2 were lower than those of HMFS_G2 and HMFS_C2.The G of HMFS_P2 was only 68.60,but it was still better than commercial formula fats.In conclusion,commercial formula fats only have shown similar fatty acid profiles to HMF,and there were still significant differences in the TAG structure between them and HMF.Therefore,HMFS with high similarity was prepared based on TAG composition,which lays foundation for the the development of human milk fat equivalent.