Effect of storage in a fruit drink on subsequent survival of probiotic lactobacilli to gastro-intestinal stresses

Nine probiotic lactobacilli strains were evaluated for their ability to survive in a commercial fruit drink stored at 4 °C for up to 80 days. The pH of the drink was 4.2, which enabled good stability of many cultures during storage. Lactobacillus rhamnosus seemed more stable than Lactobacillus acidophilus in this medium, but viability was still mostly strain dependent. Spectrophotometry studies showed that the cultures generally had higher growth rates as pH increased from 3.8 to 4.2. There was a correlation (P = 0.037) between stability during storage in the drink and the ability of the strains to grow at pH 4.2, but that the relationship was not strong (R2 = 0.49). Four strains were selected to study their resistance to simulated gastro-intestinal (GI) conditions. Fresh cultures were compared to those obtained after 35 days of storage at 4 °C. Viability in presence of 0.3% bile salts or of pancreatic enzymes was not affected by previous refrigerated storage. However, the cultures which were tested after having been stored for 35 days at 4 °C in the fruit drink had on the average 1.2 log higher viability losses than the fresh cultures when exposed to a 2 h incubation at pH 2.0 to simulate a gastric stress.