The effect of moisture and resistant starch concentration on the water activity (a(w)) and water sorption of imitation cheese was investigated. The Guagenheim-Anderson-deBoer (GAB) equation was found to be a good description of the experimental moisture sorption isotherms. Inclusion of starch in cheese increased moisture sorption over the a(w) range studied. The GAB monolayer value indicated starch-containing cheese bound an additional 1.4 g water/100 g dry matter when compared to a starch-free cheese. Increasing cheese moisture content had an insignificant effect on moisture sorption but increased a(w). Increasing starch concentration had little influence on the GAB parameters but nonetheless decreased a(w). It is believed that starch, while relatively inert in terms of water binding, may organise water molecules causing them to be physically entrapped within the cheese matrix. By not competing with protein for water molecules, the starch allowed the water to remain available for plasticization to maintain good functionality of the cheese. (C) 2007 Elsevier Ltd. All rights reserved.