Investigation of viability and some probiotic properties of probiotic bacteria in in vitro conditions and milk model system enriched with legume flours

The first section of the present study investigates the ability of Lactobacillus casei ve Bifidobacterium animalis subsp. lactis probiotic strains to ferment the legume flour extracts added in carbohydrate-free MRS (de Man, Rogosa and Sharpe) and TPY (Tryptone Peptone Yeast Extract) basal media under in vitro conditions. The basal media supplemented with 2% pea, white kidney bean, mung bean and cowpea flours extracts and inoculated with 3% bacterial culture, were incubated for 48 hours at 37⁰C under anaerobic conditions. The samples with no carbohydrate was designated as negative control whereas the samples with 2% glucose or inulin were evaluated as positive controls. Optical density (OD650), pH, enumaration of probiotic bacteria, prebiotic activity score (PAS), lactic acid and short chain fatty acids (SCFA) contents were analysed on 0, 24 and 48 hours of fermentation. When the samples were examined, it was found that probiotic bacteria counts in all samples were generally >7 log10 cfu/mL and the highest number of bacteria was observed in sample containing L. casei + cowpea flour. The content of the SCFA was bacterial species and legumes flour type-dependent. The highest content of lactic acid and total SCFA were found in samples containing white kidney bean flours. In the second section of the study, the reconstituted milk (11.11% DM) containing 2% legume flour extracts (pea, white kidney bean, mung bean and cowpea flour) and 3% L. casei and B.animalis subsp. lactis probiotic bacteria cultures was used as milk model system and the variations on microbiological, physicochemical and textural properties of fermented milk samples were determined on the 1st, 14th and 28th days of storage. According to the viable cell counts, it was observed that the viability of L. casei was higher than B. animalis subsp. lactis in the milk model system. The values for total amino acid composition and total antioxidant activity of L. casei + mung bean flour samples and the total phenolic compounds of B. animalis subsp. lactis + cowpea flour samples were higher than other milk models for flour samples. The results suggested that the in vitro and milk models with legume flours, such as pea, white kidney bean, mung bean and cowpea were good matrices for growth of L. casei and B. animalis subsp. lactis and displayed a potential prebiotic activity. Furthermore, both matrix were able to maintain the prescribed minimum viable counts of bacteria with therapeutic benefits (>7 log10 cfu/g) throughout storage.