Development of starter culture for soymilk fermentation using lactic acid bacteria isolated from raw milk

Abstract

The use of unique microbial culture with desirable qualities as starter is very essential for the processing of fermented products with exceptional and uniform organoleptic properties. Fermentation enhances the formation of organic acid in food and thus promotes shelf life. The development of starter culture from Lactic acid bacteria (LAB) recovered from raw milk for soymilk fermentation was highlighted. The LABs were isolated from raw milk using pour plate techniques on MRS agar (MRSA). Characterization and identification of isolates were performed through morphological and biochemical tests. The LABs obtained were randomly mixed and used as starter culture to initiate fermentation in five sets of freshly prepared soymilk from soya beans for four hours at laboratory conditions, and the products were subjected to proximate and organoleptic assessments following standard methods. A total of four Lactobacillus species and one Streptococcus species were obtained, all isolates were acid formers and positive to phenol tolerance. The proximate content of the fermented soymilk showed that the moisture content ranged from 93.78±0.18 to 92.38±0.04 %, the protein content ranged from 3.52±0.04 to 2.30±0.01 %, the nitrogen-free extract ranged from 0.27±0.14 to 0.99±0.00. The titratable acid was between 25.53 and 15.04, while the pH values ranged from 4.20 to 3.19, the organoleptic scores were between 53 to 84 %. The study underscores the potential of the isolated lactic acid bacteria to produce fermented soymilk with good nutritional quality that could be harnessed for product development in the local food processing industries.