Standardization of method for lactoperoxidase assay in milk

Abstract

The spectrophotometric method used to measure lactoperoxidase activity in milk was standardized. The assay system consisting of ABTS [2,2'-azinobis-(3-ethyl benzthiazoline-6-sulphonic acid)] as chromogenic substrate gave a linear initial rate of reaction up to 700 μg·L-1 lactoperoxidase concentration, with maximum activity at pH 6.0. The lactoperoxidase activity was higher in buffalo milk than cow milk and the corresponding concentration of the enzyme was 31 and 24 mg·L-1, respectively. A loss of 10-15 % of peroxidase activity occurred on the preparation of rennet whey or acid whey. © Inra/Elsevier, Paris.