Comparative Study On Composition And Secondary Structure Of Whey Protein In Human,Bovine And Goat Milk

In this study,we mainly explores the similarities and differences between the main nutritional ingredient,the mineral content,the whey protein amino acid pattern,the whey protein composition and function,and the secondary structure of the whey protein in human milk,bovine milk,and goat milk.Through the differences between human milk,bovine milk and goat milk,we can provide a theoretical basis and further study for the use of bovine milk and goat milk.The main results are as follows:(1)Analysis of the main nutrients and mineralsDetermination of the content of the main nutrients in three kinds of milk:the protein content is determined by Kjeldahl nitrogen method,the fat content is measured by ether extraction method,the dry matter content is determined by direct drying method,ash content is determined by burning method,and determination of lactose is contented by high performance liquid chromatography.For the determination of mineral elements:The mineral element potassium and sodium are determined by flame emission spectrometry,and the elements of calcium,zinc,iron,magnesium and copper are determined by atomic absorption spectrophotometry.The results show that compared with bovine milk and human milk,goat milk has more protein(3.84 g/100 g),fat(3.87 g/100 g).And except copper elements are less than human milk(0.041 mg/100 mL)in mineral content,the content of other elements is higher than that of bovine milk and human milk.(2)Analysis of amino acid pattern in whey partThis study adopts an automatic amino acid analyzer to measure the amino acid composition of whey proteins in human milk,bovine milk and goat milk.The nutritional value is comprehensively evaluated by the fuzzy recognition method based on ratio coefficient of amino acid(RCAA)and score of ratio coefficient amino acid ratio coefficient score(SRCAA).Results shows that the ratio of essential amino acids to total amino acids(EAA/TAA)in human milk,bovine milk and goat milk whey proteins are 0.426,0.429 and0.450,showing a 0.8768,0.9163 and 0.9197 similarity to whole egg protein.And a 0.9445,0.9156 and 0.9250 similarity to United Nations Food and Agriculture Organization/World Health Organization(FAO/WHO)reference protein.Goat milk's SRCAA values are 68.47 and76.56,respectively in the two patterns indicating high nutritional value which is higher than human milk with 66.78 and 74.82 value.Therefore,goat milk,compared with bovine milk,is a better source of functional foods for infants and young children.(3)Analysis of the composition and function of whey proteinwhey protein in goat milk,bovine milk and human milk are separated and combined with LC-MS identification.We found that there are 156,278 and 454 kinds of proteins in goat milk,bovine milk,and human milk's whey protein.Compared with bovine milk and human milk whey protein,there are 99 kinds of specific expression proteins in goat milk whey protein.And respectively,there are 31 and 15 kinds of protein express the same as bovine milk and human milk.According to the gene ontology(GO)annotations analysis,the whey protein of three kinds of milk in biological process is mainly the biological regulation.On molecular function,whey protein of three kinds of milk is mainly embodied in the binding effect.In cellular component,whey protein of three kinds of milk in the cell is mainly participate in the composition of organelle region and the extracellular region.KEGG pathway analysis shows that whey protein of three kinds of milk mainly involved in the complement and coagulation cascade reaction and phagocytosis.Meanwhile,it has a positive impact on human immunity.(4)Analysis of secondary structure of whey proteinUse the amides?band of fourier transform infrared spectroscopy(FTIR)to measure the natural secondary structure of whey protein in three kinds of milk.Use amide III band to analysis the uneasily distinguishable alpha helix and random curled structure.The proportion of ?-Helix in goat milk's secondary structure is 20.26% which is much closer to the human milk which has a proportion of 27.37%.To a certain extent,it will be more conducive to the absorption of the human body.Therefore,goat milk is a better raw-food materia of functional foods for infants and young children.