Evaluation of growth, sugar and organic acid metabolism and cell viability of probiotic ‎lactic acid bacteria in jujube extract

In this research, the production of a probiotic drink based on jujube extract by means of ‎fermentation with Lactobacillus plantarum and Lactobacillus delbrueckii as probiotic ‎lactic acid bacteria has been studied. The fermentation was performed for 72 hours at ‎‎37°C. The changes in microbial population, pH and titratable acidity as well as sugar and ‎organic acid metabolism during the fermentation period were evaluated‎. Appropriate growth of L. plantarum and L.delbruckii resulted in an increase in acidity to 1.86 and 1.75, and a decline in pH to 3.4 and 3.56, respectively after 72 hours. Glucose and fructose were significantly consumed by the strains. Citric acid concentration reduced to 1.12 g/l and 5.8 g/l in the extract fermented by L. plantarum and L. delbrueckii, respectively after 72 hours. Lactic acid was produced by L. plantarum and L. Delbrueckii with 23.8 and 11.4 g/l lactic acid, respectively at the end of fermentation. L.plantarum cells exhibited more resistance toward cold storage conditions. So that at the end of the third week of cold storage conditions, the viable cells of L. plantarum was 3.2 × 101 × CFU / mL, while no viable cells of L.delbruekii was observed at this week. In general, it can be concluded that the fermentation of jujube by L. plantarum and L. delbrueckii could be considered as an appropriate way to improve the functional properties of beverages.