Biofunctional Attributes and Storage Study of Soy Milk Fermented by Lactobacillus rhamnosus and Lactobacillus helveticus
Birendra Kumar Mishra1§, Subrota Hati2*§, Sujit Das1§ and Jashbhai B. Prajapati2
1Department of Rural Development and Agricultural Production, North-Eastern Hill University, 794001 Tura Campus, Meghalaya, India
2Department of Dairy Microbiology, SMC College of Dairy Science, Anand Agricultural University, 388110 Anand, Gujarat, India
Received: 30 October 2018
Accepted: 8 July 2019
soy yoghurt, ACE inhibitory activity, antioxidant activity, antimicrobial activity, isoflavones, Lactobacillus sp.
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.
*Corresponding author: +919409669561
§These authors contributed equally to this work