Characterising the synbiotic beverages based on barley and malt flours fermented by Lactobacillusdelbrueckiiandparacaseistrains

This research was conducted to study physicochemical characteristics of fermented cereal-based beverages. The changes in levels of microbial population, pH, total titrable acidity (TTA), sugars (fructose, maltose and glucose), and organic acids (lactic and citric acids) of these beverages were determined during 48 h fermentation of malt, barley and barley-malt media by two potentially probiotic strains of Lactobacillus paracasei and Lactobacillus delbrueckii. Results showed that the selected probiotics well grew on single and mixed substrates without any supplementation. The highest microbial growth (9.7 log cfu/ml) was found in malt medium after 15 h fermentation. A significant decrease in pH value to 4.25 and a considerable increase in TTA level to 2.96 g/100 g lactic acid were obtained by initial 6-h fermentation of L. paracasei on malt medium. High-performance liquid chromatography analysis showed that lactic acid and glucose, respectively, were the major produced acid and metabolised sugar in the developed beverages. Higher sugar consumption by L. paracasei in comparison to L. delbrueckii was also observed. L. paracasei synthesised 5.12, 11.22 and 7.64 g lactic acid/l in the media containing barley, malt and barley-malt, respectively. Moreover, malt-based beverages fermented with L. delbrueckii were the best sample due to the highest cell viability (1.2×106 cfu/ml) after 4 weeks under cold-storage.