Detection of Soybean Protein in Adulterated Milk by Amino Acid Analyzer

The separation and analysis of 17 amino acids in milk protein and soybean protein were conducted by amino acid analyzer. When the concentrations of amino acids were in the range of 0.025–0.350 μmol/m L, the correlation coefficients between peak areas and amino acid concentrations were above 0.988, the calibration curves of 17 amino acids all exhibited good linearity and repeatability. Mean recovery rates and relative standard derivations(RSDs) for 17 amino acids from spiked samples were in the ranges of 94.2% to 103.1%, and 0.89% to 3.31%, respectively. The linear relationship between the contents of 6 selected amino acids showing significant differences in the amino acid profiles of the two proteins and the amounts of added soybean protein was established by adulteration simulation experiments with correlation coefficients above 0.889. This study has provided a good method for qualitative and quantitative detection of soybean protein adulterated milk.