Abstract: A method for the determination of soybean protein in steak products by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. Firstly, the specific soybean peptides were identified and screened by high-resolution mass spectrometry based on the Unitprot database to obtain the peptide sequences for accurate identification of soybean protein. Then, the soybean peptide sequences were converted into ion pair information using the skyline software. Next, the specific soybean peptides were confirmed by LC-MS/MS, and further quantified. Finally, 3 peptides for quantitative analysis of soybean protein with good linearity and recovery rate were selected, which were GSDLVNVR, VSDDENNNYK, and LVCCPQQAEDDK. For all three peptides, the correlation coefficients were above 0.99, the spiked recoveries were 81.7%–115.8%, and the precision expressed as relative standard deviation (RSD) was less than 13%. The limit of detection (LOD) was 0.15%, and the limit of quantification (LOQ) was 0.5%. The soybean protein contents of 28 commercially available steaks were determined successfully using the proposed method. The results showed that the method was highly specific and accurate, and could be applied to other meat products.

Key words: liquid chromatography-tandem mass spectrometry, peptide identification, steak, soybean protein, quantitation