Process optimization strategies to reduce variability in thermal processing of packaged foods

The majority of food products (whether individual solid or liquid in pack) are thermally processed as discrete items in which the structure of the individual item is important. Even many bulk liquid or particulate foods such as canned or pouch foods are subject to a large part of their thermal processing after packaging (Best et al., 1994). Examples include cooking and cooling of baked products, manufacture of chilled or frozen ready meals, and production of confectionery. These food products are usually arranged in a systematic fashion in a process chamber with the process heat transfer fluid flowing over them. The processing chamber (oven, retort, or kiln, etc.) can be operated in batch or continuous mode. The batch sterilization of packaged foods is a classic example of such processes. For these processes, the objective is to convert the initial temperature of all the products to some required final temperature (usually within a given time) in order to ensure the destruction of any potentially harmful or spoilage organisms, quantified by the achievement of a certain sterilization value. This target must be reached while minimizing the concomitant reduction in product quality. Figure 28.1 illustrates the system under analysis with the individual products arbitrarily given a cylindrical shape.