Survival of Probiotics in Synbiotic Apple Juice During Refrigeration and Subsequent Exposure to Simulated Gastro-Intestinal Conditions

The aim of this work was to produce synbiotic apple juice and investigate the survival of Lactobacillus acidophilus and Lactobacillus plantarum in apple juice during the refrigerated storage (4 °C) for 42 days and then the ability of the mentioned probiotic bacteria in gastrointestinal tolerance under gastrointestinal tract conditions, with simulated gastric and bile juices. Eight-treatment combination Plackett-Burman design was used to evaluate the influence of seven variables such as probiotic strain, inoculum size, fructooligosaccharide content, inulin concentration, patulin content, ascorbic and citric acids concentration on the viability of mentioned probiotic strains. The results showed that the survivability of probiotics in apple juice depends significantly (P ≤ 0.05) on the inoculum size, inulin concentration, kind of probiotic strain, and ascorbic and citric acids’ concentration, respectively. The highest viability was achieved by inoculation of 108 CFU/mL of Lactobacillus acidophilus ATCC 4356 to the apple juice contaminated with 110 µg/L patulin content, containing 2.5% (w/v) inulin, 4 g/L citric acid, and 200 mg/L ascorbic acid. No significant difference was observed in the organoleptic properties of the synbiotic apple juice and the control sample. After sequential incubation in the simulated gastric (2 h) and intestinal juices (pH 7.4, 2 h), the highest number of surviving cells was around 3.5 log (CFU/mL).