Comparative Study On Protein Quality Of Human Milk,Cow Milk And Goat Milk

Objective:In order to assess difference among human milk,cow milk and goat milk,this study evaluated protein content,specific protein content,essential and non-essential amino acid levels,patterns and scores in different milk sources.The data provided a reference for the selection of the optimal milk source for infant formula,and also provided a basis for the revision of China’s infant formula standards.Methods:According to the characteristics of residents’ dietary structure and the main milk source of cow milk and goat milk,sampling points were taken.This study collected 96 human milk from Chengdu,Zhengzhou,Mudanjiang,Beijing,Nanjing and Guangzhou,12 cow milk from Neimenggu,and 12 goat milk from Shanxi.The information of the lactating mother and the basic situation of the milk sample were collected using self-designed questionnaire.The amount of total protein and 18 amino acids among different milk sources were detected by national standard method.The level of lactoferrin,α-lactalbumin and β-casein were measured using high performance liquid chromatography-tandem mass spectrometry.All data were analyzed using SPSS 24.0 statistical software.Results:1.This study included 96 individuals and human milk.The age range of lactating mother was from 22 to 32 years,which met the inclusion and exclusion criteria.The total protein content ranged from 1034.00±40.37 to 1159.00±104.29 mg/100 g among cities,the highest of which was from Mudanjiang（83.01±16.98mg/100g）and the lowest was from Beijing（62.46±8.77mg/100g）;The highest content of human milk α-lactalbumin was Mudanjiang（356.82±61.29mg/100g）,and the lowest was Guangzhou（298.10±29.67mg/100g）;the highest content of human milk β-casein was Beijing（452.44±25.18mg/100g）,the lowest was Guangzhou（338.10±112.86mg/100g）.This study just showed that BMI was significant difference in different cities（P<0.05）.However,There was no significant difference in total protein and specific protein in different cities（P>0.05）.2.Among the different milk sources,The highest total protein content was 3415.00mg/100 g in cow milk,the lowest was 1125.00mg/100 g in human milk,the highest lactoferrin content was 72.70mg/100 g in human milk,and the lowest was 4.64 mg/100 g in goat milk.The highest content of β-casein was 1432.16mg/100 g of goat milk,and the lowest was 425.85mg/100 g of human milk.There were two genotypes of β-casein in cow’s milk,namely A1 and A2,and the level were 518.44 mg/100 g and 428.87mg/100 g,respectively.The levels of total protein,lactoferrin,α-lactalbumin and β-casein were statistically significant among human milk,cow milk and goat milk（P<0.05）.The difference of α-lactalbumin between milk and goat milk was not statistically significant（P>0.05）.3.In human milk,the highest total amino acid content was 11.04±1.37 mg.g^-1 in Zhengzhou and the lowest was 7.69±1.13 mg.g^-1 in Guangzhou.Among them,the highest amino acid content was glutamic acid,and the lowest amino acid content was tryptophan.In different milk sources,the total amino acid content from high to low is milk(32.91±2.06 mg.g^-1),goat milk(30.66±2.78 mg.g^-1),human milk(10.25±1.79 mg.g^-1).The 18 amino acid contents were statistically significant in human milk,cow milk and goat milk（P<0.05）.The difference between proline,phenylalanine,tryptophan,proline and cysteine in cow milk and goat milk was not statistically significant（P>0.05）.4.The amino acid patterns from different milk sources were similar to human requirement.The amino acid scores of human milk,cow milk and goat milk were 6.39,15.07 and 14.61,respectively,and human milk was more suitable for infants（8.5）.Conclusion1.Although there is a difference in milk source between total protein and specific protein content,no geographical difference in human milk.Among them,total protein and β-casein content in human milk are the lowest,lactoferrin and α-lactalbumin are the highest,2.In different milk sources,the contents of total amino acids was cow milk > goat milk > human milk.The amino acid patterns of human milk,cow milk and goat milk were all similar to human requirement.3.The amino acid score of human milk met the nutritional requirements of infants,followed by goat milk and cow milk.