EFFECT OF HEAT PASTEURISATION ON SOME EGG WHITE ENZYMES

It has been shown by a potassium permanganate titration method that solutions of egg white decompose hydrogen peroxide. Using an oxygen electrode the 1st‐order rate constants for the decomposition of hydrogen peroxide (during the first minute of the reaction) by different samples of newly laid and laboratory heat‐treated egg white, have been calculated. An Arrhenius plot of calculated denaturation constants has shown that the activation enthalpy, free energy and entropy changes required for the heat inactivation of the catalase‐like property' were 39.8 kcal mole−1, 22.6 kcal mole−1 and 51 entropy units, respectively. The effect of heat on the lyspzyme, the a‐mannosidase and the N‐acetyl‐β‐D‐glucosaminidase enzymes of egg white has also been studied and it has been shown that the activity of N‐acetyl‐β‐D‐glucosaminidase enzyme is reduced by heat at 53 to 57°. The activation enthalpy, free energy and entropy changes required for the heat inactivation of N‐acetyl‐β‐D‐glucosaminidase were 62.9 kcal mole−1, 21.8 kcal mole−1 and 124.5 entropy units, respectively. The results are discussed with particular reference to the occurrence, disputed by some workers, of a catalase enzyme in egg white, and to a possible application of the effects of heat on the egg white enzymes as a method for measuring the effectiveness of heat pasteurisation processes. Copyright © 1969 John Wiley & Sons, Ltd