Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6405551 | LWT - Food Science and Technology | 2012 | 6 Pages |
Metabolic studies are very important to improve quality of functional dairy products. For this purpose, the behaviors of pure cultures of Streptococcus thermophilus (St) and Lactobacillus rhamnosus (Lr) as well a co-culture of them (St-Lr) were investigated during skim milk fermentation, and the inulin effect as prebiotic was assessed. Lr was able to metabolize 6Â g/100Â g more galactose than St and St-Lr. Final lactic acid production by Lr was higher (9.8Â g/L) compared to St (9.1Â g/L) and St-Lr (9.1Â g/L). Acetic acid concentration varied from 0.8Â g/L (St-Lr) to 1.5Â g/L (Lr) and that of ethanol from only 0.2Â g/L (St-Lr) to 0.4Â g/L (Lr), which suggests the occurrence in Lr of a NADH oxidase activity and citrate co-metabolization via pyruvate, both dissipating a part of the reducing power. Diacetyl and acetoin accumulated at the highest levels (18.4 and 0.8Â mg/L, respectively) with St-Lr, which suggests possible synergistic interactions between these microorganisms as well as the Lr capability of co-metabolizing citrate in the presence of lactose. Inulin stimulated both biomass growth and levels of all end-products, as the likely result of fructose release from its partial hydrolysis and subsequent metabolization as an additional carbon and energy source.
⺠Pure cultures or binary co-culture of Streptococcus thermophilus and Lactobacillus rhamnosus were studied. ⺠A synergistic interaction took place between S. thermophilus and L. rhamnosus. ⺠The co-culture produced more diacetyl and acetoin than pure cultures. ⺠Inulin stimulated biomass growth and levels of all metabolic end-products.