Water Activity and Freezing Point Depression of Aqueous Solutions and Liquid Foods

ABSTRACT Water activity (a w ) of binary aqueous solutions and liquid foods (skim milk, coffee beverages, peach and tomato juices) at different total solids concentration (by wt).was evaluated, measuring freezing point depression (FPD). The calculated values differed from those obtained by electric hygrometer by less than 0.01 a, units. Water activity was also evaluated in model systems containing ethanol, for which a w determination by conventional electric hygrometer is not possible.