In vitro assessment of gastrointestinal viability of potentially probiotic Lactobacilli

The objectives of this study were to assess the potential of four probiotic lactobacillus strains, Lactobacillus bulgaricus, Lactobacillus johnsonii B-2178, Lactobacillus gasseri B-14168 and Lactobacillus salivarius B-1950 in human upper gastrointestinal tract in vitro and evaluate the effect of milk proteins addition on viability of these strains in simulated gastric juices and in yoghurt during storage for 15 days at 4°C. The viability of lactobacilli strains in simulated gastric transit conditions (pH 2.0, pH 3.0 and pH 4.0) gastric juices with or without milk proteins singly or in combination with starch was tested. All the treatments were determined with three replicates. The simulated gastric transit tolerance of L. johnsonii ,L. gasseri and L. salivarius strains was pH- dependent and correspondingly showed lower viability at pH 2.0 after 180 min compared with pH 3.0 and pH 4.0. The addition of milk proteins singly or in combination with starch enhanced the survival of probiotic lactobacilli strains in simulated gastric juices different tested pH values. Results showed that addition of milk proteins in combination with starch improved the viability of L.johnsonii B-2178, L. gasseri B-14168 and L. salivarius B-1950 in yoghurt during storage. Sensory evaluation showed that yoghurt fortified with milk proteins plus starch recorded the highest score for and overall acceptability than the other treatments. However, yoghurt manufactured with L. johnsonii and L. gasseri and fortified with sodium caseinate plus starch showed the highest organoleptic score. It is suggested that the yoghurt of acceptable quality and high total probiotic bacterial count during storage can be made from milk supplemented with 0.5% (w/v) starch plus 0.5% (w/v) sodium caseinate. (Journal of American Science. 2010;6(11):357-367. (ISSN: 1545-1003).