Extraction and enzyme activity assays were used following the methods of Huang et al.,with some modifications.Five grams of frozen peel tissue were homogenised in 25 ml.of 0.05 mol/l sodium phosphate buffer (pH 7.0) containing 0.5 g.poly vinyl polypyrrolidone for 2 minute.The homogenate was centrifuged at 12,000 x g.for 20 minute.All steps of the extraction and assay were carried out at 4 °c.The supernatant was used as a crude enzyme solution to estimate polyphenol oxidase (ppo)activity and peroxidase (pod)activity.