ABSTRACT

The prediction of water activity（aw.） by mathematical models, in general, has been limited to aqueous solutions of electrolyte and non-electrolyte solutes. The effect of food components, such as fiber, proteins and fats, on a. has not been taken into account when those models are applied to real foods. The estimated aw. on food systems is greater than the actual value reported because of water absorbed by proteins or bound into fat mesomorphic structures. An interactive computer program developed to accuray predict the a. of multicomponent systems is able to perform the following tasks:（1） Predict the aw. of food model systems by several well accepted equations, such as Bromley,Pitzer, Norrish, Ferro-Chirife-Boquet, Ross, and Ferro-Benmergui-Chirife. （2） Establish similarity levels between foods of known a. and composition to new food products where composition is available. （3） Calculate deviation factors based on previously established similarity levels, where the presence of fibers, fats, and proteins is taken into account. The analysis of sausage-like products, in the first iteration, showed a deviation factor of 1.07,while sugar confections with gums and pectins had a deviation factor of 1.09. Once a supporting data bank is created, the deviation factor rapidly converges to one.