The knowledge requirements of the food microbiologist working with thermally processed products are very challenging; particularly in relation to minimally processed foods. In the past, the minimum criteria for sterilized canned foods was very well-defined, however, the diversity of food products, packages and related heat processes are now very difficult to summarize in terms of minimum requirements. The overall heating characteristics of these products can be complex, particularly for mixed particulate products or multicompartment packages. Similarly, the death kinetics of the contaminating micro-organisms can be markedly different dependent on the composition of the food product. These factors combined with the consumer demands for 'fresher' foods has resulted in product, process and package development and innovation progressing at a much faster rate than in the past. While food safety is the most important factor, there are also other issues such as shelf-life and visual quality that have strong market influences and must therefore also be considered by the microbiologist.