Lipid deterioration: β‐Carotene destruction and oxygen evolution in a system containing lactoperoxidase, hydrogen peroxide and halides

A model system containing lactoperoxidase/H 2 O 2 /halide decomposed β‐carotene in a reaction greatly affected by the concentration of H 2 O 2 . The optimal concentrations of H 2 O 2 for activation of iodide and bromide were 2 mM and 10 μM, respectively. The oxidation of chloride by a lactoperoxidase, using β‐carotene destruction as a sensitive method to determine the activity of the enzyme, is reported herein. In the presence of optimal amounts of H 2 O 2 , the rate of β‐carotene destruction increases slowly until a critical concentration of the halides, followed by a rapid increase in the rate when halide concentrations were furthere increased. A lactoperoxidase/H 2 O 2 /iodide and/or bromide system generates oxygen in the presence of high H 2 O 2 and halide concentrations. β‐Carotene inhibited the evolution of oxygen. A possible mechanism of β‐carotene destruction and triplet unexcited oxygen evolution by a lactoperoxidase/H 2 O 2 /halide system are proposed.