The water immersion method was used for the cooking and cooling of Lyoner type sausages prepared from minced beef and pork. Two methods were applied for calculating thermal diffusivity: the first one (A) is based on the simplified analytical solution of the equation of heat conduction in solids, and the other (B)-on the numerical solution of the heat conduction equation. Changes in temperature with time were measured at the sample centre during heat treatment. The values determined by method (A) differ significantly from the published data for different meat products. The results calculated by method (B), which ranged between 1.35 x 10(-7) and 1.52 x 10(-7) m(2) s(-1) for cooking and from 1.41 x 10(-7) to 1.75 x 10(-7) m(2) s(-1) for cooling, are in agreement with the literature data. (C) 2004 Elsevier Ltd. All rights reserved.