Peroxidase Activity Test

Method description

Samples are homogenized and enzymes are extracted into a cold, pH 6.5 buffer.  A protein determination by the Bradford method is performed on the enzyme extract (supernatant) to normalize subsequent enzyme results to the efficiency of the protein extraction.  The enzyme extract is mixed with hydrogen peroxide, guaiacol, and calcium. Peroxidase activity is measured spectrophotometrically by the rate of formation of tetraguaiacol at 470nm.

Acceptable matrices

Cereal grains, doughs, pasta, and vegetables

Equipment

UV/Vis spectrophotometer, homogenizer, microplate reader

Method reference

Britton Chance, A.C. Maehly, Method in Enzymology, Assay of catalases and peroxidases. Vol 2, Academic Press, New York, 1955, pp. 764-775.

Reportable unit

1 Unit = 0.5 μM of Guaiacol consumed per minute under assay conditions.

Sample size requirements

20 grams

Information required by submitter

Estimates of activity (if available) and composition of the sample matrix.

Additional information

Peroxidase is an enzyme that can catalyze the cross-linking of phenolic residues by H2O2 resulting in undesirable color changes (graying) and the potential generation of off-flavors in a food product. Determining the average level of peroxidase in different cultivars can help guide breeding decisions. Additionally, because peroxidases are relatively stable enzymes, they can serve as an indicator for the efficacy of enzyme inactivating treatments in grains and flours (heat treatment, chemical treatment, etc.)

Please keep and ship samples frozen, if possible.