| Human milk exists as a natural oil-in-water(O/W)emulsion,in which the fat exists as colloidal assemblies of human milk fat globules(HMFG)with sizes of 3-5 ?m.HMFG comprise triacylglycerols(TAGs)stabilized by a complex tri-layer milk fat globule membrane,which is much higher than the fat droplet size in infant formula.A recent study showed that the membrane has certain nutritional benefits due to unique membrane structure.This study provided a method of preparing stable O/W emulsion stabilized by MFGM-rich ingredient nanoemulsion.Microstructure,storage stability and hydrolysis kinetics of lipids of in vitro digestion of the emulsion were also studied.The main research contents are presented as follows.Firstly,polar lipid including phospholipids,cholesterol and ganglioside in human milk,mammal milk,infant formulas and MFGM-rich whey protein powder were detected by GC-MS,LC-MS,31P-NMR.The results indicated that the content of phospholipid in human milk was 9.23±4.87 mg/100 m L,sphingomyelin was the main phospholipid in human milk;cholesterol and desmosterol were the main sterols in human milk,and the contents were10.13 mg/100 m L and 2.12 mg/100 m L respectively.The contents of ganglioside GD3 and GM3 were 9.61±3.32 ?g/m L and 2.08±1.39 ?g/m L respectively,mammal milk contains higher content of phospholipids and GD3,but lower content of GM3.There was a significant difference in polar lipid content and composition between human milk and infant formulas.The main phospholipids in infant formulas were PC(39.65-58.13%),the cholesterol content(3.78-7.19 mg/100 m L)was lower,GD3 content(10.25-23.55 ?g/m L)was higher.Compared with soy phospholipids,phospholipids in MFGM-rich whey protein powder were closer to human milk,GD3 and GM3 were both detected in whey protein powder,and the content of polar lipid in M-10(Lacprodan(?) MFGM-10)was the highest,which contains the highest content of phospholipids(81.08±3.18 mg/g)and cholesterol(1.29±0.04 mg/g).The structure of HMFG and infant formula were characterized by confocal laser scanning microscopy,results of which showed that there was a difference in size and structure of the fat droplets between infant formulas and human milk.Secondly,present study provided a method for preparing an emulsion stabilized by nanoemulsion droplets that similar to human milk fat globules.Preparation parameters such as liquid ratio,shear rate and homogeneous pressure were optimized.The results indicated that the optimal nanoemulsion preparation conditions: the content of M-10 was 2%(w/w),shear rate was 2000 rpm(1min),homogeneous pressure was 800 bar(3 cycles),and the final emulsion preparation conditions: the content of nanoemulsion was 50%(w/w),the content of soybean oil was 40%(w/w),homogeneous pressure was 300 bar.The mean diameter of the final emulsion was 3.96±0.26 ?m,which was close to that of human milk.Finally,microstructure,storage stability and in vitro digestive properties of the emulsion were characterized.The results showed that the emulsion droplet size was 3-5 ?m and the polar lipids presented as cyclic annuli surrounding the TAG cores.The emulsions stored at 4? did not show obviously structural damage upon 7 days of storage,the deformation or partial deformation of the nanodroplets formed with M-10 at the interface may improve the physical stability of the final emulsion.In vitro digestion of the O/W emulsion showed a low lipolysis degree in gastric digestion,and the final hydrolysis efficiency of the O/W emulsion was 62.74%,which is higher than that of traditional infant formula.The emulsion droplet structure persisted through gastric digestion,and was damaged in the intestinal phase,which was consistent with the changes in the microstructure of the human milk fat globules during digestion.This research studied the polar lipids composition and the structure of fat globule in human milk,as well as the preparation of emulsion that similar to human milk fat globules.Results of present study will contribute to promoting infant formula to be closer to human milk. |
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