Probiotic viability in yoghurts containing oligosaccharides derived from lactulose (OsLu) during fermentation and cold storage

We studied the viability of probiotics Lactobacillus acidophilus and Bifidobacterium animalis ssp. lactis and microorganisms of a starter culture for set-style yoghurt, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, during manufacture and cold of storage of synbiotic yoghurts containing lactulose and the emerging prebiotic lactulose-derived oligosaccharides (OsLu). The evolution of the carbohydrate fraction, pH and microbial metabolites, such as organic acids, were assessed. Supplementation of yoghurts with lactulose significantly increased counts of Lb. delbrueckii ssp. bulgaricus, Lb. acidophilus and B. animalis ssp. lactis during fermentation in comparison with control yoghurt, in agreement with partial lactulose consumption. OsLu content was unchanged during fermentation or subsequent storage. These results demonstrated that the chemical structure of the oligosaccharide plays a remarkable role in the fermentation of probiotics, suggesting OsLu as an alternative prebiotic to conventional lactulose in dairy products with adequate cell counts of probiotics while preserving the initial levels of added prebiotic.