Antioxidative Activity of Whey Protein Hydrolysates in a Liposomal System

¹ Food Science Section Department of Animal Sciences University of Kentucky Lexington, KY 40546-0215

Whey protein isolate (WPI) with or without pre-heating (90°C for 5 min) was hydrolyzed for 0.5 to 6 h using four pure enzymes (pepsin, papain, trypsin, and chymotrypsin) and three commercial crude proteases. After determining the degree of hydrolysis, the hydrolysates were incubated (37°C 1 h) with a liposome oxidizing system (50 mM FeCl₃/0.1 mM ascorbate, pH 7.0). Lipid oxidation was measured by determining the concentrations of TBA-reactive substances (TBARS). The degree of hydrolysis of WPI ranged from 4 to 37% depending on the enzymes used and whether the substrate was heated or not. WPI hydrolysates prepared by pure enzyme treatments did not prevent TBARS formation in the oxidative model system, but WPI hydrolyzed by the commercial crude enzymes, especially protease F, exhibited antioxidant activity. The antioxidative potential of hydrolyzed WPI was not affected by the degree of hydrolysis, and it was improved by preheat treatment in only some samples.

Key Words: whey • protein hydrolysates • lipid oxidation • antioxidants

Submitted on May 21, 2001
Accepted on August 14, 2001

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