Thermal processing is one of the conventional preservation methods which assures processed foods to be safe and shelf-stable. The origin of commercial thermal processing dates back to 1809 when the Frenchman Nicholas Appert was awarded a prize by the French government for developing a new and successful means of preserving foods, a method that eventually became known as 'canning'. Appert found a new and effective way to preserve food, but did not understand why it prevented food spoilage. In 1864, Louis Pasteur, another Frenchman, explained that the heating process killed (or inactivated) the microorganisms which limited the shelf-life of foods. This laid the foundation for advances in canning methods that eventually revolutionized the industry. In the 1890s, Prescott and Underwood established the relationship between thermophilic bacteria and the spoilage of canned corn. At about the same time, the same type of spoilage was discovered in canned peas by Russell in Wisconsin and Barlow in Illinois. In the 1910s and 1920s, the basic biological and toxicological characteristics of Clostridium botulinum were first determined by several American investigators. The importance of controlling C. botulinum in canned foods became clear and the basis for its control was established. Bigelow et al. (1920) developed the first scientifically based method for calculating the minimum safe sterilization processes for canned foods. It became known as the 'original' or 'graphical' method. Ball (1923) subsequently developed theoretical methods for the determination of thermal processes. Schultz and Olson (1940) developed a nomographic method for process determinations. Most subsequent developments on the subject have been based on these early concepts. Stumbo (1949) devel oped procedures for the calculation of sterilization processes based on integrating lethality values over the entire volume of the container. More advanced mathematical methods which eliminated certain relatively small errors inherent in some of the previous mathematical procedures were developed by Hayakawa (1968). Since about 1970, in addition to Ball, Stumbo and Hayakawa, several researchers have contributed to refining the mathematical models of thermal processing further. These later works (Teixeira et al., 1969; Purohit and Stumbo, 1972; Lenz and Lund, 1977; Tung and Garland, 1979, etc.) have led to the use of computers for more accurate, rapid and routine heat process calculations and for monitoring and controlling thermal processes by on-line measurement of accomplished lethality.
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