Effect of time and enzyme type on the structural and antioxidant properties of bioactive peptides obtained from navy bean protein (Phaseolus vulgari L.)

In this study, the effect of enzyme type (alcalase and pepsin) and process time (50-300 minutes) on the degree of hydrolysis and antioxidant indices including free radical scavenging of DPPH, ABTS, hydroxyl, reducing power, and chelating activity of Iron and copper ions were evaluated for navy bean protein (Phaseolus vulgari L.). Also, the composition of amino acids (hydrophobic and antioxidants types) and structural properties (FTIR) of primary protein and hydrolysates were investigated. The results showed that enzymatic hydrolysis improves antioxidant properties. Also, the composition of amino acids has a significant effect on antioxidant activities. On the other hand, the type of enzyme and the time of the hydrolysis process affected the degree of hydrolysis and the antioxidant activity of the hydrolysates. Thus, the highest percentage of free radicals scavenging of DPPH (82.4%), ABTS (58.3%), reducing power (0.97), hydroxyl radical scavenging (57.5%), and chelation of Fe (53.7%) and Cu ions (12.1%) were affected by the type of enzyme and process time. Among different treatments, the highest value of these indices (except copper ion chelating) was related to hydrolysates with alcalase. Structural properties of white bean protein were evaluated and enzymatic hydrolysis caused changes in the amide regions (I and II) as well as exposure to some hydrophobic-buried groups. The results of this study indicated the positive effect of enzymatic hydrolysis on the production of antioxidant hydrolysates that can be used in the food industry.