[Thermal inactivation of the enzymes polyphenoloxidase and peroxidase in Swiss chard (Beta vulgaris, cicla)].

The freezing of Swiss chard has just started in Argentina. The blanching stage is fundamentally important to avoid damage of sensorial and nutritional properties during storage. If the process is not properly carried out, darkening can seriously affect the product. In this research work the thermal inactivation of polyphenoloxidase and peroxidase enzymes has been studied, in water at 80, 90 and 96 degrees C, as well as the polyphenoloxidase isoenzymes in the spear and leaf of the plant and the water-holding capacity after thermal treatment. Blanching has to be performed at a temperature higher than 90 degrees C in order to inactivate the enzyme polyphenoloxidase at a suitable rate which will avoid the formation of the characteristic colored substances.