Proteolysis and Angiotensin-Converting Enzyme Inhibitory Activity of Peptide Fractions from Pigeon Pea Tempe

Pigeon pea seeds are considered as a potential sources of angiotensin-converting enzyme (ACE) inhibitory peptides. During tempe fermentation, certain bioactive peptides including ACE inhibitory peptides can be generated due to proteolytic activity produced by tempe molds. The present study was conducted to investigate the proteolysis during pigeon pea tempe fermentation and determine the ACE inhibitory activity of peptide fractions from pigeon pea tempe. Commercial starter RAPRIMA® (0.02 % w/w) consist of Rhizopus oligopsorus spores was used to fermented pigeon pea seeds for 0-96 h. Fractionation was completed by using dialysis tube with molecular weight cut-off of 1, 3.5, and 14 kDa. The longer fermentation time resulted in greater proteolysis in pigeon pea tempe. Proteolytic activity and peptide content were reached a maximum of 0.044 U/mL and 3.175 mg/100 g, consecutively after 96 h of fermentation. All of the resultant peptide fractions from pigeon pea tempe (48 h of fermentation) could inhibit ACE activity. Low-molecular-weight peptide fractions tended to have a higher ACE inhibitory activity than high-molecular-weight peptide fractions. Among the resultant peptide fractions, Peptide fraction of less than1 kDa was found to be the most potent fraction to inhibit ACE activity with (87.98 %) while peptide fractions of greater than14 kDa had the lowest ACE inhibitory activity (61.20 %). In conclusion, peptide extract from pigeon pea tempe could become a promising source of ACE inhibitory peptides and could be used as a functional food or for other food applications.