ABSTRACT
Thermal processing involves heating foods in hermetically sealed containers for a specific time at a specific temperature to eliminate the microbial pathogens that endanger public health and microorganisms and enzymes that deteriorate food during storage. Credit for the invention of thermal processing (or canning, as it was originally called) goes to Nicholas Appert, a French confectioner. The original concept of in-container sterilization of foods, however, has come a long way since Appert first introduced “the art of canning” in 1810. As introduced and developed in the initial stages, the primary focus of canning was safety and shelf stability. Today, however, the consumer demands much more than just safe and shelf-stable food — including, primarily, higher quality food with greater convenience in the end use. And food processors look for more energy-efficient, cost-effective, and high-speed processing technologies. High-temperature, short-time (HTST) techniques have primarily evolved to minimize the severity of heat treatment and promote product quality. Continuous aseptic processing and packaging further minimize the heat severity by quick heating and cooling of the food, prior to packaging, under aseptic conditions. Thin profile, thermostable, microwavable packages have been developed for promoting faster heat transfer rates, which minimizes the heat damage to product quality while adding the convenience of package microwavability. Rotary and continuous cookers for canned foods have been based on product agitation during processing to accelerate the rate of heat transfer in order to promote better quality in processed foods. Microwave, radio frequency, and ohmic heating techniques have gained attention as alternate and nonconventional rapid heating techniques. However, although different procedures can be employed for thermal processing, it is still necessary to design a process that would deliver the required minimum heat treatment to render the food safe. In this chapter, the principles of thermal processing are detailed, emphasizing the use of process calculation methods and equipment for thermal processing.
