Effect of Clostridium butyricum combined with traditional fermenters on the quality characteristics of fermented milk

The conversion of large molecular weight ( M W ) milk into small Mw fermented milk is a complex and dynamic process that depends mainly on the selected fermenter. In this study, we aimed to investigate the potential role of co-fermentation of Clostridium butyricum (CB) with traditional fermenters-Lactobacillus bulgaricus and Streptococcus thermophilus (Y)-in improving the quality characteristics of fermented milk. The results showed that compared with the Y group only, the CB-complexed Y group (3CB-Y) with the appropriate addition amount (3 × 10 8 CFU/g) significantly increased the acidification capacity (pH = 3.9; o T = 109.5) and the number of live bacteria of the fermented milks (CB content = 2.37 × 10 8 CFU/g), and led to an increase in the water uptake by 15.6 % at the 28th d compared with the fermented milks of Y group, and a denser structure of the gel network of the fermented milks with an increase in the hardness (3.1 N), consistency (37.9 N s), Cohesion (−1.6 N), Viscosity index (11.7 N s) and ultimately improved the volatile flavour substances (86 species) and sensory qualities of the fermented milk. This study demonstrated that CB combined with Y co-culture could significantly improve the quality characteristics of fermented milk by altering the species and content of the bacilli, and the microstructure of the fermented milk. • Co-fermentation of CB with Y improved acidification capacity and live bacteria count. • WU increased by 15.6 % in the 3CB-Y group compared to the Y group. • Fermented milk with added CB has a pleasant texture and sensory qualities. • CB promotes the formation of cross-linked network structures in fermented milk. • The synergistic effect of CB and Y altered the flavour characteristics of fermented milk.