Peroxidase isoenzymes were purified from green peas with ion-exchange chromatography on DEAE-and S-Sepharose. Three isoenzymes were identified, one neutral (N) and two cationic (Cl, C2). N was extremely heat labile, with 50% original activity lost after heating 1.5 min at 25°C. N had Km values CDH 5.0) of 10.2 mM and 2.6 mM for guaiacol and H,Oa, respective'ijl. Cl and C2 retained activity on heating at 30-70°C. Cl was able to reactivate after thermal inactivation. Km values for guaiacol/H202 were 10.8 mM/7.2 mM (pH 5.0) and 10.8 mM/4.3 mM (pH 6.0) for Cl and C2, respectively. The three isoenzymes exhibited different peroxidase activities with different H-donors, different sensitivities to cyanide and different abilities to catalyze oxidation of indoleacetic acid.

Fresh green peas were blanched for various times/temperatures and stored at -23°C. At 3 month intervals peas were analyzed for peroxidase, polyphenoloxidase, lipoxygenase and catalase activity and ascorbic acid content. Samples were cooked and evaluated sensorily, and using Hunter color and Instron texture measurements. Enzymes exhibited varying degrees of activity over the first 3 months in storage. After 3 months, peroxidase and polyphenoloxidase activity decreased or remained constant. Lipoxygenase activity increased over storage, most noticeably in the long time/low temperature blanch treatment. Sensory evaluation indicated a gradual loss of quality due to poor flavor in the long time/low temperature blanch. Ascorbic acid content, greenness and firmness decreased gradually with storage.