| Healthy human milk is the best food source for infants,providing all the nutrients they need in early life.The fat content in human milk is an important nutrient,it can provide sufficient energy,essential fatty acids and fat-soluble vitamins for infants.When breastfeeding is not possible,infant formula becomes the preferred food for infants.The fat in infant formula is called human milk fat substitute(HMFS).The fat composition in commercially available infant formula is quite different from human milk,mainly due to the random distribution of palmitic acid in the triacylglycerol(TAG)and the insufficient content of sn-2 palmitic TAG.This study selected a natural lipid from one freshwater fish oil,which is rich in sn-2 palmitic TAG,and used fractionation and physical blending techniques to obtain fish oil-based HMFS similar to human milk fat.The main research includes:Firstly,the lipid composition in different regions of the fish oil was detected by gas chromatography and high temperature gas chromatography.The results showed that the total contents of palmitic,oleic and linoleic acids in fish oil A,fish oil B,fish oil E and fish oil G exceeded 80%,with values of 82.91%,83.55%,86.10%,and 87.62%,respectively.Except fish oil C,the sn-2 palmitic acid content of other fish oils was between 31.26% and 34.89%.The relative content of sn-2 palmitic acid in seven kinds of fish oils ranged from 57.08% to 69.27%according to the calculation.The main TAG in all samples was OPL(O stands for oleic acid,P stands for palmitic acid,and L stands for linoleic acid),followed by OPO.The C52 TAGs content in fish oil E and fish oil G was relatively high,reaching 47.51% and 47.07%,respectively.Overall,fish oil E was found to be most similar to human milk fat,and was selected as the raw material for subsequent experiments.Next,the solvent fractionation was used to enrich C52 TAGs in fish oil E,and the conditions were optimized.The results showed that the total palmitic acid content of fish oil E increased to 24.83%,while the total linoleic acid content decreased when fish oil E and acetone were weighed at 1:8(w/v)and extracted at-40oC for 24 h.The sn-2 palmitic acid content increased to 47.27%,and the relative content of sn-2 palmitic acid was calculated to be 63.46%.The C52 TAGs content in fish oil E after extraction was 53.56%,which was a 20.31% increase compared to before extraction.Based on the above results,solvent fractionation can effectively enrich the content of C52 TAGs in fish oil E,and the extracted fish oil E is a good raw material for preparing human milk fat substitute.Then,based on the composition of human milk fat in China,MATLAB mathematical model was used to determine the optimal ratio of HMFSs prepared by physical blending fish oil E,Trachinotus ovatus oil or Basa catfish oil with 6 vegetable oils,respectively.The results showed that HMFS-A was obtained by using fish oil E and vegetable oil as raw materials,in which sunflower oil: palm oil: corn oil: rapseed oil: soybean oil: fractionated fish oil E =0.81:0.04: 0.48: 1.98: 2.67: 7.39: 86.62.The similarity scores of total fatty acids,sn-2 fatty acids and TAG were GFA=99.26,Gsn-2FA=78.56 and GTAG=65.39,and the total similarity score G=81.07.Trachinotus ovatus oil was used as material to prepare HMFS-B,and its GFA,Gsn-2FA,GTAG and G were 91.29,77.03,69.96 and 79.42.The GFA,Gsn-2FA,GTAG and G of HMFS-C prepared from Basa catfish oil were 93.28,65.64,55.14 and 71.35,respectively.From the score,the composition of HMFS-A was more similar to human milk fat than B and C.In addition,HMFSA was the closest to human milk fat when compared with the lipid composition of commercially available plant-based oil,cow milk and goat milk based infant formulas.Finally,fish oil E-based,plant oil-based,cow milk-based,and goat milk-based HMFSs were prepared into emulsions,and their fatty acid release behavior and digestion product composition during in vitro digestion were investigated.The results showed that the maximum fatty acid release rate of the fish oil E-based emulsion was 60.94%,higher than that of the plant oil-based emulsion(53.60%),and close to that of the cow milk-based(60.13%)and goat milkbased(63.16%)emulsions.In terms of digestion products,the free fatty acids released from the fish oil E-based emulsion were mainly unsaturated fatty acids,with oleic and linoleic acids accounting for 44.23% and 22.71%;while the free fatty acids released from the cow milk-based and goat milk-based emulsions were mainly palmitic and oleic acids.The digestible product monoacylglycerol of the four kinds of emulsion were mainly monopalmitin.with the monopalmitin content of the fish oil E-based emulsion reaching 72.16%,while those of the plant oil-based,cow milk-based,and goat milk-based emulsions were 44.35%,48.62%,and46.24%,respectively.Therefore,it can be verified from the structural characteristics of TAG that fish oil E-base HFMS is beneficial to infant digestion,indicating that it has great application value in infant formula.To sum up,this paper screened out a kind of natural fish oil with rich contents of sn-2palmitate TAG,and analyzed their chemical composition in different regions.Fish oil E-based HMFS was obtained by fractionation and physical blending.It was evaluated that this product had a high similarity with human milk fat,and its digestion process was stable,which was beneficial to the digestion and absorption of infants.The results show that fish oil E has great potential in the field of HMFS and can provide better quality infant formula for Chinese infants. |
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