| Milk is considered as the closest to a perfect food in the nature,which wasvital to human health,and had a special status in the human dietary pattern.Amino acid,beingthe basic unit of protein,was the basic material of nutrition,and it was the survival and physiological activity of living organisms.It was also an important part of biological organism,which plays a vital role in all stages of life cycle.At present,there were no related domestic research reportson the total amino acid changes and analysis of nutritional evaluation of different lactation periods of cow,goat and breast milk.In this study,the contents of total protein and 18 kinds of amino acids in three kinds of milk were systematically analyzed,and the nutritional characteristics were evaluated by the amino acid evaluation model recommended by FAO/WHO in order to provide the basic references for infant formula food processing enterprises.The main conclusions are as follows:(1)The changes of three milk protein were similar:(1)the protein contents of milk colostrum was the highest at the first day after delivery,which were 17.70±0.81 g/100 g of cow's milk,13.38±0.03 g/100 g of goat's milk,2.68±0.017 g/100 g of breast milk,and then decreased rapidly.The protein contents changedgreatly at colostrum stage,and it was becoming flat after seven days.(2)Throughout the lactation period,the protein contents of the decreased slowly with the prolongation of lactation,and the average content of proteins were3.30±0.75g/100 g of cow's milk,4.06±0.83g/100 g of goat's milk,and 1.17±0.16g/100 g of breast milk.(3)Comparatively speaking,the colostrum protein content of cow was higher than that of goat in the first two days after delivery,which was lower than that of goat after three days.(3)The change of 18 amino acids content of the three kinds of milk after hydrolysis was consistent with the corresponding protein content: the Glu content of cow and goat milk was the highest,which was12.49±0.76mg/g of cow's colostrum,12.57±0.48mg/g of goat's colostrum,6.09±0.61mg/g of cow's milk,7.65±0.81mg/g of goat's milk;the Trp content was the lowest,which was1.17±0.84mg/g of cow's colostrum?1.24±0.65mg/g of goat's colostrum?0.44±0.84mg/g of cow's milk?0.54±0.47mg/g of goat's milk;the Glu content of breast milk was the highest,which was3.53±0.39mg/g of breast colostrum,2.48±0.58mg/g of breast milk,and the Met content of breast milk was the lowest,which was0.27±0.54mg/g ofbreastcolostrum,0.09±0.34mg/g of human milk.The highest content of eight essential amino acids of the three milk was Leu,which was2.70±0.65mg/g of cow's milk,3.43±0.76mg/g of goat's milk,1.32±0.16mg/g of breast milk;the Trp contentof cow and goat milk were lowest,which was 0.44±0.84mg/g of cow milk,0.54±0.47mg/g of goat's milk;the Met content of breast milk was the lowest,which was 0.09±0.34mg/g.(3)In the case of amino acids,the total essential amino acid(TEAA)ratio of total amino acids(TAA)of three kinds milkwere all higher than 36%(FAO / WHO Recommended Criteria),which were 44.68% of cow's milk,46.06% of goat's milk and 46.37% of breast milk;Based on the evaluation of nutrition,three kinds of milk belong to high quality protein resources,the performance of TEAA and TAA from the highest to the lowest was breast milk,goat's milk,and cow's milk.(4)The amino acid score(AAS)of the three kinds of milk in the model of young children(0.5-3 years old)and the population aged over 3 years were greater than 100 in the three categories of anthropogenic amino acid scoring modes recommended by FAO / WHO(2011),which were belonged to the high quality protein,and fully met the needs of the human body.In the baby(0-0.5 years old)mode,the breast milk had fully met the demand.The cow's and goat's milk slightly were less than the need,which were needed for intensive treatment.Relatively speaking,goat milk was better than cow milk.(5)In the FAO / WHO recommended mode,the protein comprehensive evaluationwas carried out by amino acid score(AAS),amino acid ratio coefficient(RC),score of amino acid ratio coefficient(SRC),essential amino acid index(EAAI).The Thr and Phe+Tyr AAS score of cow milk were the highest,which were 175.23 and 125.97 respectively.The top two of goat milk AAS score were Thr 180.39,Lys 146.71.The first and second limiting amino acids of cow milk were Met+Cys and Val,whoseAAS score were 96.40 and 94.15,while RC score were 0.82 and 0.80.The first limiting amino acids of goat milk was Met+Cys,whoseAAS score 91.63,RC 0.73.Based on a number of indicators of evaluation,human milk was the best performance of the three kinds.The indexes of goat milk werethe most similar to the breast milk.As a whole,the performance of human milk was better than that of goat milk,while goat milk was better than cow milk. |
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