The previously proposed kinetic theory of moisture migration in packaged multi-component systems is developed further and tested against experimental data. Two simplified analytical solutions suitable for implementation without special purpose software have been found. The first solution concerns the case where the moisture exchange of one component is rate limiting. The other solution describes the situation where all components are characterized by the same moisture uptake dynamics (response function). The numerical calculations using the full theory as well as the solution assuming same sorption dynamics of all components are shown to be in accordance with experimental data for the moisture transfer in closed systems containing binary or ternary mixtures of raisins, roasted almonds, peanuts and banana chips. The calculations show that the headspace water activity is distinctly different from the water activities of the components at any time indicating that no single component sorption process is rate limiting. The implications of the theory are that the information of dynamics of moisture sorption of the individual food components under constant humidity conditions can be utilized in simple expressions for the time development of component moisture contents with the possibility of making shelf life calculations on any combinations of the food components. (C) 2003 Elsevier Science Ltd. All rights reserved.