| Infant formula is developed with human milk as the standard and is the staple food for non-breast-fed infant.Nutrient composition close to human milk is one of the key technologies for infant formula production.The research on protein is relatively mature,while lipid has been recognized as a research hotspot and difficulty in the industry due to its complex composition.At present,there are several common problems including the lack of human milk lipid database,the low degree of lipid simulation,easy oxidation of lipids and poor instant solubility of products in the infant formula industry.In view of the above background,we preliminarily established a lipid database of mature human milk by analyzing the lipid profile,fatty acid composition and positional distribution of human milk from different lactation periods in Zhejiang Province.The human milk lipid simulated formula was optimized based on the systematic similarity analysis of the lipid composition between the current commercial infant formulas and human milk.Besides,the effects of mineral compound sources on lipid oxidation stability and the industrial research of human milk lipid simulated infant formula were investigated.The main results were as follows:(1)Lipid composition of human milk from different lactation periodsA total of 378 human milk samples in different lactation periods were collected from Hangzhou,Jinhua,Huzhou and Taizhou in Zhejiang Province.The macronutrient content,lipid class,fatty acid composition of lipids and sn-2 position of triglycerides,phospholipids in colostrum(0～5 days),transitional milk(6～14 days)and mature milk1～4 stages(15～30 days,31～90 days,91～180 days,181～360 days)were analyzed.The results showed that the proportions of cholesterols and phospholipids in the lipids,and the relative percentages of C16:0,C18:1n-9(oleic acid),C22:6n-3(DHA)and C22:4n-6(ARA)in the fatty acids of colostrum were significantly higher than those of mature milk,while the levels of C10:0(decanoic acid),C12:0(lauric acid),C14:0(myristic acid),C18:2n-6(LA)and C18:3n-3(ALA)were significantly lower than those of mature milk.C12:0,C14:0,C16:0,ARA and DHA were mainly located in the sn-2 position of triglycerides,while C18:1n-9,C18:2n-6 and C18:3n-3 were primarily distributed at the sn-1,3 positions.Compared with human milk reported in western countries,samples in our study demonstrated higher percentages of LA,ALA,ARA and DHA,but lower levels of C12:0,C14:0 and C18:1n-9.Based on the research,a lipid database of mature milk(15～180 days)covering lipid profile,fatty acid composition and positional distribution was established.The results provided useful data for the development of human milk lipid simulated formula for Chinese infants.(2)Human milk lipid simulation degree of the current commercial infant formulasThe lipid composition including phospholipid class,fatty acid composition of lipids and sn-2 position of triglycerides of 27 commercial infant formulas were determined,and compared with mature human milk by using the similarity analysis.The results showed that the similarity of lipid composition between commercial infant formulas and mature human milk was only 70.80±4.36%.The main differences were as follows: the proportion of phosphatidylserine in phospholipids and the relative percentages of C12:0,C18:1n-9,ALA in lipids of commercial infant formulas were significantly higher than those of human milk,while the proportion of sphingomyelin in phospholipids and the levels of DHA and ARA were significantly lower than those of human milk;infant formulas demonstrated significantly different percentages C14:0,C16:0,C18:1n-9,LA,ALA,ARA and DHA in sn-2 position of triglycerides compared with human milk.This indicated that the degree of human milk lipid simulation of the current commercial infant formulas still had many aspects to be optimized for improvement.(3)Optimization of human milk lipid simulated formulaIn view of the low similarity of lipid composition between commercial infant formulas and human milk,a human milk lipid simulated basal formula was optimized by using MATLAB optimization toolbox.The formulas of human milk simulated DHA,ARA and phospholipids were developed by optimizing the raw lipid materials.The results showed that the fatty acid composition(including the relative percentages of C12:0,C14:0,C16:0,C18:0,C18:1n-9,LA,ALA,DHA,ARA in the lipids and the proportions of C12:0,C14:0,C16:0,DHA,ARA in sn-2 position of triglycerides)and the phospholipids composition were consistent with that of human milk lipids,when the optimized formula of infant formula is 6.444% milk fat,7.027% corn oil,0.784%sunflower oil,3.157% rapeseed oil,1.706% coconut oil,0.064% palm kernel oil,7.197%1,3-dioleoyl-2-palmitoylglycerol(OPO),1.449% DHA,1.158% ARA,0.010% soybean phospholipid,2.814% milk fat globule membrane.(4)Effects of mineral compound sources on the lipid oxidation stability of human milk lipid simulated infant formulaBased on OXITEST method to evaluate the oxidative stability,a rapid evaluation method for evaluating the lipid oxidation stability of infant formula was established based on the time to reach the lowest point of oxygen pressure as the evaluation standard by studying the oxidation profile of lipids at different stages.In view of the problem of easy oxidation of lipids in infant formula,the influence of mineral compound sources on the lipid oxidation stability of human milk lipid simulated infant formula was studied.The results demonstrated that the strong and weak effects on the lipid oxidation stability of infant formula was iron > copper > zinc,and the use of gluconate compound minerals can reduce lipid oxidation.(5)Industrial research of human milk lipid simulated infant formulaBy analyzing the correlation between the particle size distribution and wetting time and dispersibility of commercial infant formulas,the mathematical models of particle size distribution of infant formula with ideal instant solubility were established.The instant solubility of human milk lipid simulated infant formula was improved by optimizing the production process.The similarity of lipid composition between the industrialized infant formula and mature human milk was 81.48%,which is 10.68%more similar than the current commercial infant formulas.Clinical researches showed that human milk lipid simulated infant formula had nutritional efficacy of softening stools and promoting absorption of calcium and saturated fatty acids(SFAs)in infants.In addition,the lipid simulated infant formula containing lactoferrin could improve infant bone density,increase the content of intestinal endocrine immunoglobulin A,which can prevent food allergies and intestinal infections in newborns. |
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