Abstract: In this study, the antioxidant capacity of different donkey blood hydrolyzate was compared with DPPH radical scavenging rate and total antioxidant capacity as evaluation index. Through the test results, the hydrolysate with the strongest antioxidant activity was obtained. The enzymatic hydrolysis time, temperature, pH and enzyme-substrate ratio were optimized by single factor test and response surface method, and the actual antioxidant activity was verified by experiment. The final optimized hydrolyzate was ultrafiltered, and the antioxidant activities of different ultrafiltration components were tested. On the basis of single factor test and response surface method, the optimum enzymatic hydrolysis conditions of papin hydrolyzate were 55 ℃, pH 7, time 3.54 h and enzyme substrate ratio 20%. Under this condition, the DPPH radical scavenging rate of the hydrolysate was 71.50% and the total antioxidant capacity was 1.53 mmol/g. After verification, the DPPH radical scavenging rate of the actual enzymatic hydrolysis product was 70.40%±1.33%, and the total antioxidant capacity was （1.51±0.25）mmol/g. The antioxidant acitivity of the ultrafiltration component 3 （<3 ku） was determined to be the strongest, with DPPH radical scavenging rate of 71.26%±5.63% and the total antioxidant capacity of （1.49±0.36） mmol/g. The above results indicated that the donkey blood hydrolyzate treated with papain and its ultrafiltration component had excellent effects on antioxidant activity and radical scavenging.

Key words: donkey blood, bioactive peptides, antioxidation, DPPH radical, total antioxidant capacity