Activities of Saccharomyces cerevisiae invertase and sugar beet o-diphenol oxidase were relatively resistant to treatment with high electric field pulses (HEFP) irrespective of the conductivity, pH and concentration of their solutions and the number of electric pulses. The electric field strength ranged between 3 and 60 kV/cm and the number of pulses varied from 1 to 30. The yeast invertase was relatively resistant to HEFP treatment when the electric field strength ranged between 3 and 15 kV/cm since it lost only 10%-20% initial activity. When the electric field strength was increased to 17, 20 and 60 kV/cm, the activity of invertase was decreased by approximately 30%, 90% and 100%, respectively. Activity of o-diphenol oxidase contained in the raw sugar beet juice Was not reduced by HER treatment. (C) 2009 Elsevier Ltd. All rights reserved.