Oxidation of Methionine in Gelatin

Abstract

The oxidation of methionine residues in gelatin was studied by use of hydrogen peroxide as an oxidizing reagent. One mole of methionine reacted to 1 mole hydrogen peroxide. The oxidation was second order reaction. Rate constants at various temperatures were calculated. Activation enthalpy and entropy were 52 kJ·Emol^-1 and-110 J·Emol^-1·EK^-1 at pH 5.5, respectively. These values in gelatin were similar to the published values for methionine residues in low molecular protein and/or free methionine. This suggested that the main chain of gelatin did not influence the reactivity of methionine residues. The oxidation rate of free methionine was more rapid at pH 8.5 than pH 5. However, methionine residues ingelatin were oxidized to the same extent within the pH range from 5 to 8.5.