59D-1 |
Fractionation of hydrolyzed whey protein isolates and characterization for antioxidant activity. |
E. A. PEÑA-RAMOS, Food Science Section. Department of Animal Sciences, University of Kentucky, 206 W.P. Garrigus Bldg., Lexington, KY 40546-0215 and Y. L. Xiong. Interest in utilizing natural antioxidants has increased substantially in recent years and this has led to new investigations into using protein hydrolysates as a potential source of natural antioxidants. The antioxidant activity of whey protein isolate (WPI) appears to be related to the nature and composition of the different peptide fractions produced depending on the protease specificity. It is possible that individual fractions may vary in their antioxidant activity. The objective of this study was to separate antioxidant peptide fractions from WPI hydrolyzed with different crude enzymes and from commercial hydrolyzed WPI. A 10% WPI solution was hydrolyzed for 1 h at 50°C with 3 different commercial crude proteases. Hydrolyzed WPI samples, and 2 commercial WPI hydrolysates, were subjected to fractionation by size-exclusion chromatography using a Sephadex column. Peptide fraction elution was monitored by measuring absorbance at 280 nm. Antioxidant activity of WPI fractions was measured with a liposome oxidizing system (50 µM FeCl3/0.1µM ascorbate. Lipid oxidation was measured by determining the concentrations of TBA-reactive substances (TBARS). Fractions were also characterized by SDS-PAGE. TBARS assays indicated the presence of antioxidant activity in all the protein fractions, including the nonhydrolyzed WPI. For native and treated WPI samples, the first fraction (> 45 kDa) showed a relative higher TBARS inhibition effect (26.9 -24.3%), when compared with other lower molecular weight fractions and hydrolysate mixtures (11.9 - 23.5%). In contrast, for commercial WPI hydrolysates, the highest inhibitory effect was found on those fractions with low molecular weight peptides (<5 kDa) (30 - 50% TBARS reduction). The presence of a higher antioxidant activity in some WPI hydrolysate fractions suggests that these fractions can be a potential source of natural antioxidants.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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