Untargeted metabolic footprinting reveals key differences between fermented brown milk and fermented milk metabolomes

Fermented brown milk has gained popularity because of its unique taste and flavor. Lactobacillus bulgaricus ND02 is a starter culture that has good milk fermen-tation characteristics. This study aimed to profile the metabolites produced during Maillard browning and to identify metabolomic differences between fermented brown milk and fermented milk produced by the ND02 strain. This study used liquid chromatography-mass spectrometry to compare the metabolomes of milk, fer-mented milk, brown milk, and fermented brown milk. Significant differences were observed in the abundances of various groups of metabolites, including peptides, AA, aldehydes, ketones, organic acids, vitamins, and nucleosides. The Maillard browning reaction signifi-cantly increased the intensity of a wide spectrum of flavor compounds, including short peptides, organic acids, and compounds of aldehydes, ketones, sulfur, and furan, which might together contribute to the unique flavor of brown milk. However, Maillard browning led to an increase in N epsilon-(carboxymethyl)lysine, which might cause negative health effects such as diabetes, uremia, or Alzheimer's disease. On the other hand, fermenting brown milk with the ND02 strain effectively countered such an effect. Finally, 5 differentially abundant me-tabolites were identified between fermented brown milk and fermented milk, including l-lysine, methylglyoxal, glyoxal, 2,3-pentanedione, and 3-hydroxybutanoic acid, which might together contribute to the different nutri-tional qualities of fermented brown milk and fermented milk. This study has provided novel information about the Maillard reaction and compared the metabolomes of the 4 types of dairy products.

Automated summary

This study compared the metabolomes of milk, fermented milk, brown milk, and fermented brown milk using liquid chromatography-mass spectrometry. Significant differences were observed in the abundances of various groups of metabolites. The Maillard browning reaction increased the intensity of flavor compounds in brown milk, but also led to an increase in a substance that may have negative health effects. Fermenting brown milk with the ND02 strain effectively counteracted this effect, and differences in metabolites between fermented brown milk and fermented milk were identified, contributing to their different nutritional qualities.