Viability of streptococcus thermophilus, lactobacillus delbrueckii ssp. bulgaricus, lactobacillus acidophilus and lactobacillus casei in fermented milk supplemented with isomalto-oligosaccharides derived from banana flour

Commercial yoghurts and yoghurt-type products do not always fulfill the minimum requirement of viable culture cell counts at the time of consumption, which is the most important factor in order for such products to exhibit therapeutic effects. This work aimed to investigate the survivability of Streptococcus thermophilus, combined with Lactobacillus delbrueckii ssp. bulgaricus, and Lactobacillus acidophilus, combined with Lactobacillus casei, in two fermented milk samples supplemented with isomalto-oligosaccharides (IMO) prepared from banana flour. The preferential fermentation of oligosaccharides by the combined starter cultures was also investigated. After 28 days of storage at 4 °C, the viable cell numbers of all bacterial strains in both samples were not changed (p > 0.05). Lactose, isomaltotriose, isomaltotetraose, and maltooligoheptaose and larger oligomers, were depleted by approximately 50%, 40%, 20% and 20%, respectively. The decrease of lactose and IMO in both fermented milk samples did not differ (p > 0.05). In this study, IMO could maintain the viable cell numbers of all bacteria used in the experiments. The order of oligosaccharide fermentation preference of the cultures was lactose > isomaltotriose > maltooligoheptaose and larger oligomers > isomaltotetraose.