Excerpt from page 3.
Understanding how to prevent food spoilage is the key to canning safety. In the air and all around us are invisible microorganisms, such as mold, yeasts and bacteria. Many of the microorganisms are beneficial to us, while others can be harmful under certain conditions. All fruits, vegetables and meats, in their natural state, contain these mircoorganisms to some degree. Enzymes, which change the color, texture and flavor of foods, are also naturally occurring. Molds, yeasts, bacteria and enzymes are the major causes of good spoilage. Controlling "the spoilers" allows us to keep foods beyond their typical storage period.
Washing fresh produce removes some of the spoilers. Peeling or blanching fruits and vegetables reduces even greater numbers. The most important factor in controlling spoilers is controlling the environment which encourages their growth. This is achieved by properly heat processing the food following tested home canning guidelines.
Canning interrupts the natural decaying process by heating the food contained in a jar, closed with a two-piece vacuum, sealing cap, to a specific temperature and holding it there for the time designated by a tested home canning recipe. The heat destroys potentially harmful microorganisms and, at the same time, drives air from the jar. Upon cooling, a vacuum is formed and the lid seals onto the jar, preventing other micoorganisms from entering and recontaminating the food. This procedure is also known as processing. When followed exactly, the processing methods and times in this book adequately destroy normal levels of heat-resistant microorganisms, ensuring home canned foods will be free of spoilage as long as the jar is stored properly and remains vacuum sealed.