Evaluation of the antioxidant potential of whey protein concentrated by ultrafiltration and hydrolyzed by different commercial proteases

Abstract The objective of this work was to evaluate the antioxidant and antimicrobial activities of whey protein hydrolysates obtained using different commercial proteases (Alcalase and Flavourzyme) as well as their blend (50:50 ratio). Prior to the enzymatic hydrolysis, the whey was concentrated by ultrafiltration using tubular ceramic membranes. The enzymatic reaction was carried out according to the pH-stat method, in which aliquots were collected with different degrees of hydrolysis (DH) during the protein hydrolysis. The protein hydrolysates were evaluated with respect to the estimated peptides content, antioxidant activity by capture of free radical ABTS+ and the peroxyl radical (Oxygen radical antioxidant capacity - ORAC) methods, electrophoresis and antimicrobial activity. The maximum DH values reached were: 15%, 52% and 63% for Flavourzyme, the blend of enzymes and Alcalase, respectively. The antioxidant activity increased with the DH. The protein hydrolysates obtained using Alcalase presented higher antioxidant activities than the other samples. However, no samples presented antimicrobial activity against Salmonella choleraesuis subsp. Enteritidis (ATCC 13076) or Listeria monocytogenes (ATCC 9117).