Fermentation and metabolic profiling of brown fermented milk co-fermented with Lactobacillus helveticus H11 and PYS-010

Co-fermentation using functional lactic acid bacteria strains provides a promising approach to improve the quality and health benefits of fermented dairy products. This study examined the effects of the commercial starter PYS-010 (containing Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) and stabilizer on the physicochemical properties and metabonomics of brown fermented milk prepared using Lactobacillus helveticus H11, and the changes of metabolic flavor during storage. The combination of L. helveticus H11 and PYS-010 significantly shortened fermentation time, improved viscosity, water-holding capacity, and texture, and showed peak angiotensin-converting enzyme inhibitory activity on d 7 and 14 of storage. Nontargeted metabolomics revealed that the addition of PYS-010 significantly changed the metabolism of amino acids and fatty acids fermented by a single L. helveticus H11 strain. Further dynamic monitoring of the group fermented using L. helveticus H11 with 0.5% stabilizer and 0.003% PYS-010 during storage revealed that W5S, W2W, sourness, and saltiness sensor responses could serve as indicators for storage duration. On d 21, the contents of arachidonic acid, butyric acid, and l-malic acid increased significantly. This study provides a comprehensive view on the fermentation characteristics and metabolic changes of L. helveticus H11 during co-fermentation with PYS-010.