Stability and functionality of synbiotic soy food during shelf-life

- Heteropolysaccharide by probiotic culture in soy medium shows molecular mass >39 KDa.
- Functional synbiotic soy foods showed viable counts and fibres above legal levels.
- Prototypes contain Bifidobacterium in high counts (>7 logCFU/mL) during shelf-life.
- Calcium lactate have negative effects above 5 g/L on soy food stability.
- Best prototypes of synbiotic soy food adjusted to Hershel- Buckley rheological model.

Synbiotic soy foods fermented by lactic acid bacteria suffer pH decrease, viscosity and syneresis changes during storage. Lactobacillus rhamnosus LR32 (LR) has capacity of producing exopolysaccharides (EPS) when inoculated in complex media. A Plackett & Burman experimental design was carried out to investigate the effects of LR (plus standard probiotic mixture: Lactobacillus spp and Bifidobacterium sp), sucrose, soy extract (SE), calcium lactate (CL), fructooligosaccharides (FOS) and polydextrose on the responses: EPS, syneresis, apparent viscosity, rheological behaviour and viable counts during 30 days of shelf-life. EPS producing showed a heteropolysaccharide with molecular mass >39 KDa. CL showed the greatest significant positive effect on the syneresis, while sucrose and polydextrose showed significant negative effects. Sucrose and SE had a significant positive effect in most stability responses. The best tests for the stability study for the synbiotic and fermented soy food were without CL, added with 12% sucrose and 10% SE.