Jack bean as tempe ingredients: The safety study and fate of protein against gastrointestinal enzymes

This study evaluated the change of hydrogen cyanide (HCN) content and concanavalin A (Con A) activity during the processing of jack bean tempe. In addition, the fate of protein of cooked tempe following in vitro gastrointestinal digestion was also investigated. The jack bean tempe was prepared by the step of the soaking-boiling-soaking-boiling-fermentation process. The mature tempe was harvested on 48 h of fermentation and followed by the cooking process for 10 min (T10) and 20 min (T20). The results showed the soaking, soaking-boiling, soaking-boiling-soaking, and soaking-boiling-soaking-boiling were able to decrease the HCN content of jack bean as much as 3.98; 85.88; 92.88 and 97.95, respectively. It did not significantly change during fermentation with content for mature tempe was as low as 0.71 ppm, which is categorized as a safe level according to FAO. The haemagglutination assay of Con A showed the protein extracted from raw jack bean provided red blood cell clotting, while it was not found in the protein extracted from boiled jack bean and jack bean tempe. In the in vitro digestion model, both T10 and T20 samples showed that there was no significant change in peptides content before and after hydrolysis using pepsin (p<0.05). The action of gastrointestinal enzymes improved the released of the bioactive peptides which have the ability to inhibit angiotensin - I - converting enzyme (ACE). It can be concluded that the jack bean was the safe protein source for consumption as tempe. Furthermore, the protein of cooked tempe was highly hydrolyzed following in vitro gastrointestinal digestion produced bioactive peptides with high ACE inhibitory activity. © Published under licence by IOP Publishing Ltd.