| The fat of human milk or infant formula,which can provide the infant with energy,nutrients and biological active substances etc.,is important for the infant's growth and physiological development.In the study,the emulsions with different structure triglycerides were prepared and then the in vitro digestion experiment was carried out.The physical properties and structure of the milk fat globules as well as its fatty acid composition of the human milk and infant formulas were analyzed comparatively.And the in vitro digestion model was used to study changes of the digestion rate,the fatty acid composition of digestion production,the interfacial properties and microstructure during digestion.In addition to the in vitro experiment,the digestion and absorption of infant formulas in rats were evaluated.The emulsions with two type triglycerides(non-OPO and OPO)were prepared and the in vitro digestion was conducted,in which their digestibility,the change of the interfacial properties and the fatty acid composition of free fatty acid and monoglyceride generated from digestion were measured.Results showed that the degree of gastric digestion of OPO emulsion was greater than non-OPO emulsion,the degree of gastrointestinal digestion of control emulsion was greater than OPO emulsion.After gastrointestinal digestion 150 min,the more free saturated fatty acids and unsaturated monoglyceride were generated by control emulsion than OPO emulsion which generated more unsaturated free fatty acids and saturated monoglyceride.The distribution of fatty acid affected the digestion production which then affected the interfacial composition thereby the fat digestion.The changes of particle size and potential during digestion with the microstructure showed that very small amount of flocculation was observed in the gastric digestion 30 min,aggregation and flocculation were seen in the gastrointestinal digestion 120 min with non-OPO emulsion.The flocculation was appeared in the gastric digestion 30 min but was broken in the gastrointestinal digestion 120 min,besides the phenomenon that oil particles into larger particles was found with OPO emulsion.This study on the physical properties of human milk and infant formulas(IF1,IF2,IF3 and IF4)found that the particle size distribution of human milk fat globule was wider than that of infant formulas;the charge of human milk fat globule(-7.85 mV)was obviously less than infant formulas(-26.73~-29.90 mV).The microstructure observed with laser confocal microscope with nile red and FITC labeled showed that TAG in the form of different particle size of spherical droplets dispersed in the centre of the human milk fat globule,in which protein existed as a thin interfacial film or assembled block.In the infant formula microstructure,the particles were small and distributed evenly.The microstructure with Rh-DOPE labeled showed that a phospholipid coating was totally or partially at the surface of human milk fat globules while little or no lecithin was added to the infant formulas.The analysis of fatty acid composition showed that the %sn-2 SFA of the human milk fat was 74.97%,which of infant formulas were less than 53%.Though the sn-2 PA of infant formulas were less than human milk,IF1 and IF3 fat was similar to the human milk fat relative to IF2 and IF4.The digestion rate,changes of interfacial properties and microstructure of infant formulas and human milk in vitro digestion were studied.Results showed that the degree of gastric digestion was HM > IF2 > IF1,IF4 > IF3,the degree of eventual gastrointestinal digestion was HM > IF1,IF3 > IF2,IF4.The CLSM images showed at the end of human milk gastric digestion,the native fat globules and protein aggregation were observed and the aggregates were smaller and then resolved from 60 min to 120 min in intestinal digestion.While a large number of aggregates were observeded during digestion of infant formulas.Compared with IF3,IF4 was more likely to cause flocculation and aggregation.The fat digestion and absorption of infant formulas were evaluated by use of SD rats.After 15d's feeding experiment,the content of stomach and intestines,excrement fatty acid composition were analyzed.Results showed that the growth and feces excretion of rats had no significant difference.The fecal fat excretion of IF1 and IF3 was less than IF2 and IF4.The calcium absorption of rats was IF3>IF1,IF4>IF2.When comparing the free FA of the gastrointestinal content with the acyl chains initially esterified in infant formulas,it appeared that the level of stearic acid and palmitic acid increased while oleic acid decreased,suggesting that oleic acid was more easily absorbed.The apparent fat absorption after intake of IF1 and IF3 was significantly higher than the other two groups.It can thus be concluded that the sn-2 high proportion of palmitic acid improves fat and calcium absorption. |
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