ABSTRACT
The activity and kinetic parameters of the enzyme polyphenol oxidase (PPO) in crude extracts of the fruits ofParadise apple (Pyrus malus L.), cucumber (Cucumis sativus L.), squash (Cucurbita pepo L.), pomegranaterind and seeds (Punica granatum L.), and the leaf of cactus (Opuntia ficus-indica (L.) were investigated. Thehighest browning intensity was found in P. apple, followed by pomegranate seeds and cucumber fruits. Theoptimum activity of the enzyme was shown at pH 7.0 for P. apple and cucurbita, but it was found at pH 6.0 forthe rind and seeds of the pomegranate. The PPO of cactus leaf and cucumber fruits showed two peaks at pH 4.0and 7.0. On the other hand, the optimal temperature found for PPO activity in these plants was around 40°C.A strong correlation with value (R) = 0.9485 between the browning intensity and PPO activity in all studiedsamples was obtained.