The validated model was formally established by orthogonal projections to latent structures discriminant analysis (OPLS-DA), significant components were separated into one predictive component, t1, to describe the differences and one or more orthogonal components to filtering the irrelevant noise, the two datasets may be the most distinguished on score chart . After exporting the model correlation factor p(corr) and variable importance projection (VIP) as well as the load value, the loading diagram was drawn after backtracking transformation, and then differential metabolites were identified.