The microbiological stability and safety of sous vide products is mainly determined by the different thermal treatments including heating, cooling and reheating. Some theoretical aspects of the different modes of heat transfer relevant to 'sous vide' cooking are summarized. It is shown that computational techniques such as the finite element method and CFD (computational fluid dynamics) provide a powerful means to investigate the effect of modifications in the process conditions and equipment characteristics on the internal temperature of the food. An adequate vacuum appears to be a major factor to obtain an acceptable heat transfer rate. This may lead to better process design in terms of safety, reliability and uniformity of product quality.