Analysis And Evaluation Of Proteins And Amino-Acids In Fresh And Traditional Fermentated Non-Bovine Milks In Western China

To compare the difference in protein and amino acids profile of non-bovine milk from yak,goat,camel,horse in Western China,126 representative milk samples including fresh and traditional fermented non-bovine milk were obtained and analysed in variance analysis,principal component analysis(PCA)and nutritional evaluation based on Kjeldahl,high performance liquid chromatography(HPLC).The results showed that:(1)There were significant differences in protein and amino acid content of fresh non-bovine milk between different species and differences regions(P<0.05).(1)Species difference: protein content from high to low were yak milk,goat milk/camel milk,horse milk,fresh camel milk and fresh goat milk showed no significant difference in protein(P>0.05).The protein content of traditional fermented yak milk was the highest,the traditional fermented camel milk was the second,traditional fermented horse milk was the lowest(P<0.05).(2)Regional differences: The protein content of fresh yak milk had significant regional differences in Qinghai and Gansu(P<0.05),and the protein content in Gansu was 0.46 g/100 g higher than that in Qinghai.(3)Differences in traditional fermentation: The protein content of Qinghai traditional fermented yak milk was significantly higher than that of fresh yak milk in the region(P<0.05),and the protein content in traditional fermented milk was 0.60 g/100 g higher than that in fresh milk.(2)There were significant differences in species and regional differences in the content and proportion of amino acids in the milk of special breeds(P<0.05).There was no significant difference betwween the fresh and the traditional fermentated milk(P>0.05).(1)Species difference: There was a positive correlation between the total amount of 17 total amino acids(TAA)and protein content in five regions(P<0.05): fresh goat milk/fresh yak milk> fresh camel milk> fresh horse milk.The highest and lowest contents of the four milks were Glu and Trp respectively.Among the nine EAAs,Leu was the highest,followed by Lys,Val,and IIe.Although the content of amino acids in milk from different species were different,the proportion of amino acids in the four kinds of milk in TAA was similar to that in the whole.The content of Trp,Asp,Arg,Pro,and Ser in fresh horse milk were the lowest among four kinds of milk,but the percentage of TAA in the four kinds of fresh milk were the highest.Thr,IIe and Glu accounted for the highest percentage of TAA in camel milk,and Tyr,Met,Val,Leu and Lys accounted for the highest percentage of TAA in fresh yak milk.(2)Region differences: The amino acid contents of fresh yak milk and fresh camel milk had regional differences(P<0.05).The amino acid contents of yak milk in Gansu was 4.01 mg/g higher TAA than that in Qinghai,and Glu,Ser,His,Thr,Arg,and Ala.The contents of Phe,IIe,Leu and Pro were significantly different in fresh yak milk in two regions.The difference between Leu and Glu in fresh camel milk were significant,and the content in Xinjiang were higher.There was no significant difference in TAA of fresh milk between Xinjiang and Inner Mongolia(P>0.05).The percentages of His and Gly in goat milk were significantly higher than those of other species.In all milk EAA/TAA and EAA/NEAA were over 40%(except horse milk about equal to 40%)and 70%,respectively,which were higher than protein standard recommendations of FAO/WHO(40% and 60%).The BCAAs/TAAs in different species were higher than 20%,and the DAA/TAAs were higher than 60%.(3)Differences in traditional fermentation: By comparing the content of 17 kinds of amino acids in 3 types of fresh milk and their traditional fermented milk in 4 regions,the content of amino acids in TAA and EAA of milk were slightly lower than that of fresh milk respectively,but there was no significant difference(P>0.05).(3)There was no significant difference in fresh milk and fermented milk(P>0.05).PCA analysis indicated that corresponding feature amino acids of milk from various species were different: Arg,Ser,Ala,Trp in horse milk,Thr,IIe,Phe,Glu in camel milk,Lys,Met,Val,Tyr,Leu in yak milk,and Gly,His in goat milk.It was also found that Inner Mongolia horse milk was sweeter than other kinds of milk,and the Gansu yak milk had the most intense frankincense.(4)The results of the amino acid scores(AAS)and the essential amino acid index(EAAI)showed that 4 types of fresh milk and 3 kinds of fermented milk were high quality protein sources for adults and children over 0.5 years of age,and slightly less than the standard for infants below 0.5 years old.This study could provide some basic data for the development and utilization of fresh and fermentated non-bovine milk in western China.