Tempeh Fermentation Improves the Nutritional and Functional Characteristics of Jack Beans ( (L.) DC)

The effect of two processing methods of Jack beans ( cooked bean (CB) and cooked tempeh (CT)) on the digestibility of protein and starch, as well as the production of short chain fatty acids (SCFAs), γ-aminobutyric acid (GABA), and tryptophan (Trp) metabolites after colonic fermentation, was investigated. CT was obtained by fungal fermentation after cooking under acidic conditions. CT had significantly higher protein, lower digestible starch, lower total fiber, higher free phenolic compounds, and higher ash content compared to CB. CT exhibited better protein digestibility than CB and less glucose release during digestion than CB. A comparable concentration of total SCFAs and GABA was produced after fermentation of CB and CT, but CB produced more indole than CT, resulting in higher amounts of total Trp metabolites. In summary, our findings show that tempeh fermentation improves the nutritional quality of Jack beans and describe the impact of fermentation on the digestibility of nutrients and the formation of metabolites during colonic fermentation.