Authenticity identification of animal species in characteristic milk by integration of shotgun proteomics and scheduled multiple reaction monitoring (MRM) based on tandem mass spectrometry

Milk is one of the oldest natural dairies with high value, which has different species including cow, camel, donkey, goat, sheep, buffalo, yak and et al. However, economically motivated adulteration of non-cow milk with cheaper cow milk occurs frequently. To develop a high-throughput approach for milk species authentication, integration of shotgun proteomics and scheduled multiple reaction monitoring (MRM) was developed. In total, 37 specific peptides were screened as unique to different species. Specific peptides processing stability was investigated under different treatment (heat, pressure, fermentation). Subsequently, four quantitative ion pairs of peptides from cow milk and six quantitative ion pairs of peptides from six non-cow milks were selected for the adulteration quantitative analysis. The method is capable of detection adulteration in the range of 1%-100%, and the quantitative recoveries ranged from 91.07% to 111.75%. The results suggested that combination of shotgun proteomics and MRM had potential for the milk species authentication.