Antioxidant activity of bioactive peptides derived from bovine casein hydrolysate fractions

Bovine casein hydrolysates were prepared by enzymatic hydrolysis using trypsin alone and with a combination of trypsin and pepsin at different time intervals. Tryptic hydrolysate prepared at 4 h showed the highest antioxidant activity (13.7 %). Crude casein hydrolysate (CH) was further fractionated into 2 main types by using ultrafiltration with two different molecular weight cut-off at 10 kDa and 1 kDa. The crude hydrolysate was then compared with the collected permeates. Crude hydrolysates and the permeates, using trypsin showed radical scavenging effect by 13.7, 17.3 and 24.4 %, respectively. Furthermore, a reduced radical scavenging effect of 13.1, 15.5 and 19.6 % was observed by the combine action of pepsin and trypsin. Ultrafiltration fractions and crude hydrolysate showed the radical scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) by 1 kDa > 10 kDa > crude hydrolysate. The combined effect of trypsin and pepsin did not prove to be effective in radical scavenging. However, fractionation by ultrafiltration proved to be effective in radical scavenging. Bioactive peptides < 1 kDa possess the potential to be used in physiologically functional foods or pharmaceutical industries.