Inactivation of sugar beet polyphenoloxidase by steam blanching

Activity of polyphenoloxidase in sugar beets grown in the trial field of th e Turkish Sugar Research Institute was measured by an indirect method. Heat treatments on 2 mm thick cossettes of beet were carried out at different t emperatures and pressures. Afterwards the polyphenoloxidase was extracted a nd its activity in the reaction with catechol was determined by using a pho tometric measurement. The slope of the linear part in the first two minutes in the absorbance-time graph was taken as the total enzyme activity (Delta A(420)/s). The highest activity of sugar beet polyphenoloxidase was observ ed at pH = 7.0. In this study, the Zc value for sugar beet polyphenol-oxida se was determined as Zc = 41.52 degrees C.