Use of lactulose as prebiotic and its influence on the growth, acidification profile and viable counts of different probiotics in fermented skim milk

Lactulose can be considered as a prebiotic, which is able to stimulate healthy intestinal microflora. In the present work, the use of this ingredient in fermented milk improved quality of skim milk fermented by Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis in co-culture with Streptococcus thermophilus. Compared to control fermentations without lactulose, the addition of such a prebiotic in skim milk increased the counts of all probiotics, with particular concern to B. lactis (bifidogenic effect), the acidification rate and the lactic acid acidity, and concurrently reduced the time to complete fermentation (t_pH4.5) and the pH at the end of cold storage for 1 to 35 days.