Probiotic lactic starter cultures for soybean-based functional beverages

MOLINA, V.; BELFIORE, C.; TARANTO, M.P.; AGUIRRE, L.; LEBLANC, J.G.; VERA, J.L.; FONT DE VALDEZ, G.

Jaén, España

Congreso; Food Safety Under Extreme Conditions. A conference on small-scale production units of traditional fermented foods; 2004

FAO

The functional foods are a steady growing new branch within the ferment food market where lactic acid bacteria (LAB) play an important role. Soybean-based foods are being developed and introduced in many developing countries in Latinoamerica as a source of high quality low cost proteins. However, the raw material has certain components (antinutritional factors), which could be reduced by using selected strains of LAB with proper technological and probiotic properties. In the present study the following species Lactobacillus reuteri, L. bulgaricus, L. casei and Streptococcus thermophilus (six strains in total) as pure and multiple starter cultures in homemade and commercial soymilk (SWE, Soybean Water Extract) under different fermentation conditions were evaluated. The bacterial growth was determined by plate dilution methods, the production of vitamin B12 by HPLC and biological assays, and the end products (organic acids) and the amino acids released during soymilk fermentation by HPLC/GC. The ability of both the selected LAB strains (pure and multiple starter cultures) and the fermented SWE to stimulate the immune system response in an experimental animal model was evaluated by determining the phagocytosis index (%) of the activated peritoneal macrophages (LeBlanc et al, 2002, J Dairy Sci., 85:2733-42). All the strains were able to grow in SWE with differences in the growth kinetics. Lactic acid was the major end product although some LAB strains also produced heterofermentative end products such as acetate and succinate. Some LAB strains were able to produce vitamin B12 in SWE although at a lesser extent than in culture broth. The lactic fermentation enriched by 1.7, 1.2, and 3.0 times the SWE with amino acids of nutritional value like respectively, lysine, arginin and ornithin, respect to unfermented SWE.  Some LAB strains produced a significant increase (30 to 60%) in the phagocytosis index as well as in the production of immunoglobulins (IgA and IgG). These results are encouraging for developing novel soy-based fermented beverages by using probiotic LAB.