Formation of ACE-inhibitory peptides during fermentation of jack bean tempe inoculated by usar Hibiscus tiliaceus leaves starter

Abstract

Jack bean is one of the potential legumes as a source of ACE-inhibitory peptides in tempe fermentation due to its high protein content and amino acids composition. A traditional inoculum for tempe fermentation is usar from Hibiscus tiliaceus leaves. The aim of this study was to investigate the optimum tempe fermentation time inoculated using usar on the formation of ACE-inhibitory peptides. The study applied the prolonged tempe fermentation (120 h) at room temperature (+30°C). The change of pH, soluble protein, protease activity, and ACE-inhibitory activity during tempe fermentation were determined using standard methods. There were significant differences (α=0.05) in pH, proteolytic activity, soluble protein content, and ACE-inhibitory activity during tempe fermentation. The highest protease activity was produced at 96 h of fermentation while the highest soluble protein content was produced at 120 h of fermentation with the value of 12.71 unit/g and 3.65 mg/mL, respectively. The highest ACE-inhibitory activity was reached at 72 h of fermentation (53.89 %). Conclusion: The optimum fermentation time of the formation of ACE-inhibitory peptide was at 72 h of fermentation.