Antioxidant and angiotensin I converting enzyme (ACE) inhibitory activities of date seed protein hydrolysates prepared using Alcalase, Flavourzyme and Thermolysin

Date seed flour was used to produce protein hydrolysates using Alcalase (AL), Flavourzyme (FL) and Thermolysin (TH). Enzymes were used individually or in combination at a constant pH and temperature. The degree of hydrolysis ranged between 11 and 14%. The molecular weights of peptides determined, using a quadrupole orthogonal time-of-flight hybrid tandem mass spectrometer, ranged from 2062.9 ± 0.0 to 116,803.8 ± 0.4 Da. AL hydrolysate showed the lowest reducing power and ABTS radical scavenging activity, but a higher ACE inhibition and hydroxyl radical scavenging. Among all treatments, hydrolysates prepared using a combination of AL and FL exhibited the highest reducing power and metal chelation and high scavenging for ABTS, DPPH, hydroxyl radicals as well as ACE inhibitory activity. Combinations of AL and TH exhibited the highest ACE inhibitory activity with an IC50 value of 0.53 mg/mL. These results indicate that date seed protein hydrolysate could be used as a potential health promoting ingredient with antioxidant and ACE inhibitory activities.