Effect of controlled lactic acid fermentation on selected bioactive and nutritional parameters of tempeh obtained from unhulled common bean (Phaseolus vulgaris) seeds.

BACKGROUND: Tempeh is a traditional Indonesian food of high nutritional quality obtained by fungal fermentation of dehulled, soaked and cooked legumes. The aim of this research was to study the effect of Lactobacillus plantarum DSM 20174 activity on selected parameters of tempeh made from unhulled seeds of common bean (Phaseolus vulgaris). Lactobacillus plantarum cells were applied during soaking of seeds (submerged fermentation) or during solid state fermentation with Rhizopus microsporus var. chinensis (co-cultivation).
RESULTS: Tempeh obtained from common beans contained 200 g kg⁻¹ protein of 34% in vitro bioavailability. Fungal fermentation caused decomposition of raffinose, stachyose and verbascose levels in seeds, on average by 93, 84 and 73% respectively. Enhanced antiradical (DPPH•, ABTS•+) capacity was accompanied by increased soluble phenol content. Application of Lactobacillus in the fermentation procedure increased tempeh protein and in vitro protein bioavailability by 18 and 17% respectively. Mixed culture tempeh contained lower levels of stachyose (25%), verbascose (64%) and condensed tannins (20%). Co-cultivation enhanced both DPPH•-scavenging activity and antioxidant capacity.
CONCLUSION: The application of Lactobacillus in most cases improved the nutritional parameters of tempeh from unhulled common beans. It may also be recommended to obtain products with diverse antioxidant properties as compared with fungal fermentation alone.