Biological Activity of Ethanol in Relation to its Vapour Pressure. Note 1: Inactivation of Polyphenoloxidase in Model Systems

The relationship between the inactivation of enzymes by ethanol and its vapour pressure was studied in a simple model system containing polyphenoloxidase (PPO). The residual activity of PPO incubated in the temperature range from 15 to 90°C in the presence of increasing amounts of ethanol was evaluated. For each temperature of incubation, the residual activity of PPO as well as its thermal stability decreased as ethanol concentration increased. PPO activation energy obtained by the Arrhenius model indicated that the efficiency of ethanol increased as temperature increased. PPO activity was significantly correlated by a simple equation with water and ethanol vapour pressure. In addition, PPO inactivation appeared to be strongly affected by the vapour pressure of water andor ethanol. Measures of vapour pressure were concluded to be suitable for the study of the inactivation effect of ethanol towards the enzyme when changes in both concentration and temperature are involved.