ABSTRACT

Most foods intended for human consumption are of biological origin, except for the obvious exceptions of salt, water, etc., and it is important that this basic fact is not forgotten. Biological systems are seldom inert; during the course of life, the metabolism of the living organism changes to create the end product of the adult animal, or continuously produces the leaves, tubers, buds and seeds of the plant. Pick an apple, net a herring or pod a pea, and you will halt the metabolic processes. The animal or plant will die and so cease to grow. During its life, it possessed a complicated and highly efficient mechanism of protection from bacteria, yeasts and moulds. With death, this mechanism no longer operates. The condition of the living plant or animal will change over time but, after death, changes occur that are likely to be cumulative, irreversible and largely deteriorative unless steps are taken to halt them. It has always been one of the primary objectives of research in the food industry to develop and perfect techniques for arresting these changes during the necessary periods of distribution and storage. Food can be preserved in a number of ways, e.g. smoking, drying, canning and freezing. Other methods such as pickling and the use of salt, oils, sugar or syrups alter the characteristics of the food in order to preserve it.