The presence of residual endogenous quality-related fruit and vegetable enzymes in either raw or processed
fruit or vegetable products may cause loss of quality during processing or storage. The content and properties of such
enzymes in these raw sources vary widely with type, species, and variety of the sources and the nature of the
environment in which they grew. This study was carried out to determine the optimum conditions (pH and temperature)
and total initial activities of three quality-related oxidative enzymes [peroxidase (POD), polyphenol oxidase (PPO), and
lipoxygenase, (LOX)] in three fruit varieties; mango (Mangifera indica var. Zebda), banana (Musa cavendishii var.
Enana), (peel and pulp), olive (Olea europaea var. Picual) and three vegetables; green beans (Phaseolus vulgaris var.
Littel Marvel), tomatoes (Lycopersicon esculentum var. Marmand), cucumber (Cucumis sativus var. Ria) grown in
Egypt. The POD, PPO and LOX activities were detected in the six examined homogenates. The optimum pH and
temperature values for high enzyme activities were varied according to the type of fruits and vegetables. The highest
amount of POD was found in green beans extract (0.207 unit mg-1 protein of the sample) and the lowest amount was for
banana peel (0.087 unit mg-1 protein). However, the green beans extract had the lowest content of PPO. In contrast, the
highest content was for banana peel. For LOX activity, the mango extract exhibited the greater extent (0.249 unit mg-1
protein) than cucumber and tomato extracts (0.228 and 0.211 unit mg-1 protein, respectively). The activity of LOX was
very low in the crude banana pulp homogenate (0.068 unit mg-1 protein).