In earlier years, the preservation of food was essentially related to survival. In the more sophisticated atmosphere of today's developed nations, food-preservation techniques have sought also to bring variety, peak freshness, and optimum taste and flavor in foods at reasonable cost to the consumer. With the development of nuclear technology, isotopic materials, and machine radiation sources in recent years, the possibilities of applying ionizing radiation to the preservation of foods attracted the attention of investigators in the United States and throughout the world. An early hope that irradiation might be the ultimate answer to practically all food preservation problems was soon dispelled. Interest remained, however, in the possibility that it would serve as a useful supplementary method for counteracting spoilage losses and for preserving some foods at lower over-all costs than freezing, or without employing heat or chemicals with their attendant taste alterations.
Microorganisms are often responsible for the rapid spoilage of foods.
Of special concern is the growth of bacteria such as Clostridium botulinum which generate poisonous products. Enzymatic action in stored food produces changes which can adversely affect the appearance of food or its palatability. Spoilage by chemical action results from the reaction of one group of components in the food with others or with its environment, as in corrosion of the walls of metal containers or the reaction of fats with oxygen in the air to produce rancidity. Sprouting is a naturally occurring phenomenon in stored potatoes, onions, carrots, beets, and similar root vegetables. Insect infestation is a problem of importance chiefly in stored grain.