ABSTRACT
Most foods are dispersed systems; in other words, they are physically heterogeneous. This means that their properties are not fully given by their chemical composition. For a homogeneous liquid, like apple juice or cooking oil, it is often reasonable to assume that thermodynamic equilibrium exists. In such a case, full knowledge of chemical composition will, in principle, give all properties, including reactivity, of the system, for given external conditions (temperature, pressure, etc.). A heterogeneous system has structural elements, and making these mostly costs energy. The system is therefore not in thermodynamic equilibrium; it can be manufactured in various ways, leading to a variety of structures. The properties of the system are determined by its structure and by the chemical composition of its structural elements.
