Gas chromatography-mass spectrometry and non-targeted metabolomics analysis reveals the flavor and nutritional metabolic differences of cow's milk fermented by Lactiplantibacillus plantarum with different phenotypic

This study comprehensively evaluated the effects of Lactiplantibacillus plantarum T1 and CSK (ropy and non-ropy phenotypes), on flavour, and nutrient metabolites of fermented milks using gas chromatography-mass spectrometry and non-targeted metabolomics. The microrheological analysis showed that the protein gelation time of CSK fermented milk was earlier (5.2 h) than that of T1 (7.0 h), while the fermented milk by T1 had higher elastic modulus. Fermentation by both strains significantly enhanced the antioxidant activity of the fermented milk, including scavenging capabilities against ABTS, DPPH, and hydroxyl radicals. Meanwhile, fermentation by two strains produced various volatile flavor compounds (hexanoic acid, caprylic acid, capric acid, nonanal, decanal, 2-heptanone and 2-nonanone, etc.), and L. plantarum CSK displayed more stronger acid production capacity. In addition, a total of 397 shared metabolites and 81 unique metabolites were identified by untargeted metabolomics analysis of the two groups of fermented milks, mainly including lipids and lipid-like molecules (66, 27.27%), organic heterocyclic compounds (40, 16.53%), phenylketones and polyketones (23, 9.5%), and organic acids and their derivatives (49, 20.25%). Furthermore, both strains significantly elevated the amino acid nutritional levels in the fermented milk, conferred an abundance of active metabolites such as niacin and nicotinamide. During the fermentation, L. plantarum CSK notably produced antioxidant fumaric acid and exhibited higher fatty acid metabolism compared to L. plantarum T1. Overall, this study provides some practical basis for the development of fermented cow's milk with good antioxidant activity and high nutritional quality using different phenotypes of L. plantarum.