The Sporicidal Action of Hydrogen Peroxide and the Use of Crystalline Catalase to Dissipate Residual Peroxide

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Abstract
The washed spores of 4 aerobic spp. of bacteria were exposed to H2O2 (Superoxol) in phosphate buffer soln. After the required period of reaction, the residual H2O2 was decomposed by sterile crystalline catalase prepd. from beef liver by the method of Sumner and Dounce. Counts were made by the plate method. The logarithmic curve for survival of spores exposed to 1% H2O2 at 50[degree]C (pH 6.9) indicates that the rate of killing of most, and possibly all, of the spores ia descr. by the unimolecular law for chemical reactions. pH affects the sporicidal activity of H2O2 largely through its effect upon the stability of the H2O2. In neutral spins, the sporicidal action of H2O2 tends to increase with rising temps. An exception to this rule was observed between 30 and 40[degree]C. The time required for the killing of spores by H2O2 increases as the conc. of spores is increased, and decreases as the conc. of H2O2 is increased. Complete destruction of the spores in a culture requires appreciable time even when high concs. of H2O2 are used. Milk sterilized by H2O2 supports the growth of Escherichia coli, Pseudo-monas aeruginosa and Alcaligenes bookeri as well as milk sterilized by heat. Milk sterilized by H2O2 retards the growth of Streptococcus lactis; this is probably caused by the high oxidation-reduction potential of the milk. The appearance and odor of milk sterilized by H2O2 are the same as those of raw milk; its flavor is only slightly inferior to the latter if the treated milk is heated to 80[degree]C for 15 min. immediately after H2O2 treatment. Milk containing spores is sterilized more quickly by this combination of heat and H2O2 than by H2O2 alone. Upon long standing, milk treated with H202 develops an objectionable oxidized flavor.