Effect of Hydrogen Peroxide and Heat on Some Characteristics of B-Lactoglobulin

Model systems of fl-lactoglobulin AB in simulated milk dialysate plus 57o lactose were treated with hydrogen peroxide (.01 to .10%,w/v).Peroxide was dissipated with catalase before or after a heat treatment of 85 C for 12 rain.No discernible changes in the composition and physical properties of the protein were encountered for samples subjected to hydrogen peroxide alone.However, when peroxide was present during the heat treatment, all the protein sulfhydryls were destroyed and partially (at .01%H202) or totally (at .10%HoO2) , converted to cysteie acid.Methionine residues were reduced from 7 to 45% in the heated H202-eontaining samples.Neither methionine suIfoxide nor methionine sulfone was detected in the amino acid chromatograms.Turbidity measurements and acrylamide gel electropherograms indicated that presence of peroxide during heat treatment inhibited aggregation of fllactoglobulin.Nonprotein nitrogen determinations on heated samples indicated that there was no significant breakdown in the peptide chain.