Abstract: Heat stability of two major enzymes in vegetable processing, such as endopolygalacturonase from Rhyzopus oryzae and polyphenoloxidase from Borago officinalis, has been calculated. Isothermal and nonisothermal methods for the calculation of z values have been assayed. No significant differences between the kinetic parameters obtained by both isothermal and nonisothermal methods were found. The calculation of heat resistance of the endopolygalacturonase showed the absence of a bimodal inactivation profile. Furthermore, the present study shows the adaptation of the linearly increasing temperature method to determine the kinetic parameters of heat inactivation of those enzymes. It should be feasible to use this methodology to estimate the effects of heat treatments on the inactivation of critical enzymes.