利用同位素标记相对和绝对定量技术结合高效液相色谱-串联质谱技术对不同泌乳期人乳与牛乳中游离氨基酸的种类及含量进行检测及对比分析.结果表明,人乳中游离氨基酸种类较牛乳更为丰富,含量也高于牛乳,且随着泌乳时间的延长其总量呈下降趋势.牛初乳、牛常乳、人初乳和人常乳中游离氨基酸总量分别为0.32、0.16、0.63 g/L和0.37 g/L.实验测定的42 种游离氨基酸中,人常乳中检出35 种,牛常乳中测得31 种,其中人常乳中有25 种游离氨基酸的含量高于牛常乳,人乳中组氨酸、苯丙氨酸、苏氨酸等含量显著高于牛乳(P<0.05),游离谷氨酸在人初乳、人常乳、牛常乳中含量均为最高,而牛初乳中游离牛磺酸含量最高.本研究分析了人乳、牛乳中游离氨基酸种类和含量的差异,可为详细的研究母乳氨基酸功能和氨基酸代谢组学提供了一定的理论依据,也可为生产婴幼儿奶粉和功能性乳制品提供参考.%This study aimed to detect and compare the free amino acid composition in human and bovine milk at different lactation stages using isobaric tags for relative and absolute quantification (iTRAQ) combined with high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) (HPLC-MS/MS-iTRAQ). The results indicated that human milk contained more types and higher contents of free amino acids compared with bovine milk. In addition, the total content of free amino acids showed a declining trend during the whole lactation period. The total contents of free amino acids were 0.32, 0.16, 0.63 and 0.37 g/L in bovine colostrum, bovine milk, human colostrum and human milk, respectively. Among 42 free amino acids detected in this study, 35 were found in human milk and 31 in bovine milk. Moreover, the contents of 25 free amino acids in human milk were higher than in bovine milk. In particular, a significant increase in histidine, phenylalanine and threonine were observed (P < 0.05). The content of free glutamic acid was the highest in bovine milk, human colostrum and human milk, while taurine was the most abundant free amino acid in bovine colostrum. Understanding the differences in free amino acid composition between human milk and bovine milk can lay a theoretical foundation for detailed studies on amino acid functions and metabolomics in human milk. In addition, this study can provide a basis for producing infant milk powder and functional dairy products.
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