Biofunctional Attributes and Storage Study of Soy Milk Fermented by Lactobacillus rhamnosus and Lactobacillus helveticus.

Different soybean products are considered as traditional functional food among the Mongolian population in Northeast India. In the present study, the effect of different flavours (mango, orange, vanilla and white rose), inoculation rates of Lactobacillus rhamnosus K4E (KX950834) and Lactobacillus helveticus K14 (KU644578), and mass fractions of skimmed milk and sugar on the acceptability of soy yoghurts was studied. Physicochemical (pH, titratable acidity) and microbial analyses (total bacterial, total coliform, yeast and mould count) were conducted, and organoleptic (aroma, taste, colour, mouthfeel, texture and overall acceptability) and biofunctional properties (angiotensin-converting enzyme (ACE) inhibitory activity, antioxidant and antimicrobial activities and biotransformation of isoflavones) were evaluated during storage up to 10 days under refrigeration conditions (6-8 °C). Panellists preferred white rose soy yoghurt more than other flavours. The pH was from 5.65 to 4.20, the titratable acidity (expressed as mass fraction of lactic acid) was from 0.33 to 0.51% and total Lactobacillus count ranged from 6.81 to 8.69 log CFU/mL during storage. The ACE inhibitory activity increased from 21.17% on day 0 to 81.03% on day 5, followed by a decrease of the activity after 10 days (38.85%). The antioxidant activity was the highest on day 5 (87%). White rose soy yoghurt had the highest antimicrobial activity against Listeria monocytogenes, followed by Bacillus subtilis, Staphylococcus aureus, Salmonella typhi and Escherichia coli. RP-HPLC analysis showed that after 18 h, the production of soy isoflavone aglycones genistein and daidzein in yoghurt was 87.3 and 58.4%, respectively.

Techno-functional characterization of indigenous Lactobacillus isolates from the traditional fermented foods of Meghalaya, India.

The rural tribal people of Meghalaya depend mostly on their ethnic fermented foods as a part of their regular diet and these fermented foods are considered to be a hub of healthy microorganisms. However, the efficacy of probiotic microorganisms is considered to be population-specific because of gut microflora variation in food habits and specific host-microbial interactions. Hence, a strong need for exploring novel indigenous microorganisms with rich probiotic potentiality is required. A few indigenous Lactobacillus isolates (from traditional fermented foods of Meghalaya) were studied extensively for its technological and probiotic attributes. The isolates could survive at pH 2-3 (L. fermentum K16 showed high cell count: pH 2-5.12 log CFU/ml; pH 3-5.76 log CFU/ml), against bile salts (L. fermentum K7 showed high cell count-5.36 log CFU/ml), gastric juices (pepsin and trypsin), and intestinal juice (pancreatin). The isolates showed α-galactosidase activity from 0.104-0.412 µM/ml and ß-glucosidase activity ranging from 0.122-0.409 µM/ml. Exopolysaccharide production was in between 410 and 950 mg/L. Cell surface hydrophobicity was 71.57% (L. rhamnosus K4E) and auto-aggregation was 83% (L. fermentum K16) during the study. Highest proteolytic activity (0.671 nm) and cholesterol assimilation (52.57%) was exhibited by L. fermentum K16. The isolates showed high free radical scavenging activity by ABTS method up to 80.78% by isolate L. fermentum K7. Antibacterial activity and co-aggregation efficacy was also tested against B. cereus, E. faecalis, S. dysenteriae, S. aureus, E. coli, L. monocytogenes, S. typhi. These indigenous Lactobacillus isolates with high probiotic potentials could be exploited in the development of the traditional fermented foods of Meghalaya.