The objective of this paper was to study the effect of heat treatments on polyphenol oxidase and peroxidase activities in some fruits and vegetables, as well the possible regeneration of these enzymes after canning. In general, for the fruits, polyphenol oxidase presented more resistance to be inactivated than peroxidase and in the case of the vegetables the inverse ocurred. Concerning to the enzyme regeneration after canning, the phenomenon was evident only in the case of the peroxidase which showed great stability in adverse conditions found during heat processing. Polyphenol oxidase, for his turn, showed to be a very heat sensitive enzyme, as no regeneration was observed during the storage time of the processed products.