Untargeted mass spectrometry-based metabolomics approach unveils molecular changes in milk fermented by Lactobacillus plantarum P9

This study applied the ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry metabolomics to investigate changes in the metabolites of fermented milk with novel probiotic Lactobacillus plantarum P9. The analysis of changes in viable counts and acidity during fermentation and storage indicated that the P9 strain fermented the milk effectively and reached a fermentation end point (pH 4.5) after 13.5 h. The fermented milk was relatively stable after 28-day of cold storage. These results suggested P9 was a suitable starter culture for fermented milk production. Significant differences were observed in the milk metabolome after fermentation and after different periods of cold storage. A total of thirty-five differentially abundant metabolites were identified, including 25 significantly increased and 10 significantly decreased metabolites in the fermented milk. These metabolites included fatty acids, peptides, carbohydrates, and other metabolites, some of them could offer functional attributes to the final products. No previous study has evaluated metabolomics changes of P9 during fermentation and storage. Thus, our data provide a valuable reference for the future development and improvement of fermented dairy products using the P9 strain.