Heat stability of soluble and ionically bound peroxidases extracted from apples

Abstract

Summary Soluble and ionically bound peroxidases were extracted from apple peel and apple pulp, and activities were measured; most occurred in the soluble fraction of peel. The soluble peroxidases consisted of both cationic and anionic types of isoenzymes, whereas those ionically bound were solely cationic. Five different isoperoxidases were found by isoelectric focussing. The soluble extract of apple pulp contained the most heat stable peroxidases. After heat treatment of extracts some activity regenerated. The pH optima for the mixed peroxidases in extracts were pH 5.0 to 6.0. A commercial fresh apple juice was found to contain a small amount of peroxidase activity when assayed at pH 6.0.