Twenty microliters of enzyme extract was added to 2ml of reaction mixture consisting of a solution of 0.1 M Tris–maleate buffer (pH 6.5), 25 mM guaiacol and 25 mM H2O2. Polyphenol Oxidase activity was determined by measuring oxidation of 0.2 M catechol at 410 nm in 0.1 M sodium phosphate buffer (pH 6). Enzymatic activities were expressed as enzymatic unit g?1 FW.