To account for microbial reduction and food quality changes, first-order chemical reaction was added to a model for axial-dispersed plug flow (ADPF), which was recently developed for efficient (In the terminology of this paper, efficient is related to computation time for a given level of accuracy.) computation of time-dependent, large flow systems. It was shown that the extended ADPF model gives accurate results for typical parameter values in liquid-food applications. The analysis was based on Laplace transforms and the models were written in the object-oriented language Modelica, as objects in a library structure which is being developed to simulate complex liquid-food process lines and their control systems. The models were also implemented in such a way as to efficiently account for non-isothermal reactions in heat exchangers. Furthermore, to account for changes in flow rates, a model of dynamically calculating the "true" holding time in a channel was developed. Simulations showed that the model performs better than a straightforward alternative. (C) 2007 Elsevier Ltd. All rights reserved.