Effect of enzyme type and hydrolysis conditions on the in vitro angiotensin I-converting enzyme inhibitory activity and ash content of hydrolysed whey protein isolate

P>Removal of salts from protein hydrolysate mixture on large scale is very difficult and relatively inefficient. Selecting practical proteinase system and hydrolysis conditions for the production of whey protein isolate (WPI) enzymatic hydrolysates with high angiotensin I-converting enzyme (ACE) inhibitory activity and low ash content is very useful. The effect of alcalase, neutrase, trypsin and their combined system, i.e. alcalase-neutrase and trypsin-neutrase, under two different hydrolysis conditions, i.e. pH-controlled and pH-spontaneous drop, on the formation of ACE-inhibitory peptides and the characteristics of WPI hydrolysate was investigated. Results showed that the ACE-inhibitory activity of WPI hydrolysate obtained with alcalase was significantly higher than that of its trypsin or neutrase hydrolysate obtained at the same hydrolysis time by both pH-controlled and pH-spontaneous drop method (P < 0.05). The WPI hydrolysate obtained after 3 h incubation with alcalase plus 2 h with neutrase under pH-spontaneous drop condition possessed the highest ACE-inhibitory activity of 54.30% and the lowest ash content of 2.95%. This is practical as a functional ingredient in the food industry because of its high ACE-inhibitory capability, commercial availability in large supply of alcalase and neutrase and no needing for additional desalting process.