The development of a chemical analogue of thermal destruction of bacterial spores : a thesis presented in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Massey University
Canning as a method of food preservation has its origin in the work of Nicolas Appert (1750-1841) who was the first to use heat as a means of preserving food in hermetically sealed containers. Although he did not understand the principles of his method, his systematic experimentation (and generous sharing of his discoveries) laid the foundations of thermal food preservation methods. Appert initially processed his food in cork sealed glass jars and bottles in boiling water baths for periods varying from 15 minutes to two and a half hours. Storage trials were the basis of his processing methods, some foods being kept up to ten years. His products ranged from meats, soups and vegetables to fruit and even cream and evaporated milk. He recognized the value of quick clean handling of good quality raw materials. Blanching was used with some products, and he was also aware of the distinction between acid and low-acid foods in regard to their length of processing. Appert's understanding of the process was that heating eliminated the "air" which was believed to be the cause of spoilage. This belief was to persist for nearly 100 years. Appert's work in glass containers led to the development in England about 1815-20 of tin containers for preserved foods. Appert himself used cans in some of his later work. Some time before 1830 the autoclave was introduced (apparently by Appert) as a means of cooking canned foods under pressure. By 1870, autoclaves were being used quite widely in industrial canning.