INFLUENCE OF WATER ACTIVITY ON ETHANOL VA POR-PRESSURE IN FOOD MODEL SYSTEMS

The presence of ethanol in food is very common: it: can be found in fe rmented Foods as a consequence of fermentation processes as well as in formulated foods. Ethanol affects either sensorial properties or shel f life of food but despite its widespread use as a antimicrobial agent , few studies have been carried out in order to evaluate the mechanism s at the basis of its preservative action. The inhibitory effect of et hanol is principally attributed to its vapour pressure rather than to the ethanol adsorbed in the medium, although the latter may affect the growth indirectly through the lowering of the water activity. In this research note the influence of a on ethanol liquid-vapour partition w as studied in food model systems. Results showed that keeping constant ethanol concentration and temperature, the decrease in a(w) caused a strong increase in ethanol vapour pressure.