These substances, widely used in the more industrialized countries, are normally defined as non-nutritive substances which are intentionally added to food, generally in small quantities, to improve its appearance, flavour, texture or storage properties. Although not contaminants in the strict sense, they may give rise to harmful chemical changes and should be regarded as potentially toxic materials. For example, nitrates or nitrites are widely used as preservatives, but have been found to cause methaemoglobinaemia, especially in young children, and may give rise to carcinogenic nitrosamines. Certain non-nutritive sweetening agents (such as cyclamates) have been widely used in recent years, but it has been found that bladder tumours develop in animals to which they are fed in relatively high doses. As a result, the use of these agents has been restricted or completely prohibited in a number of countries.
By 1989, there were already 20,000 food additives used in food manufacture in the USA.
There are more than 31 artificial colours and more than 2,000 artificial flavours. A single strawberry flavour of ice cream can contain as many as 55 different additives.
Most additives are use to replace flavours and colour destroyed by processing, disguise second-rate (and sometimes bad) food, and turn basic and relatively cheap ingredients into costly 'convenience' foods. Some additives are harmless, but some are known to be health risks, among them the azo coal tar dyes used for colouring, particularly the yellow dye Tartrazine, E102 and the dyes E104-133, 142, 151 and 154-155; the benzoate preservatives, E210-213; and the purine flavour enhancers, E627-635.
Food scientist, toxicologists and control officials mention food problems in the following decreasing order: microbial contamination of food, natural toxicants in food, environmental contamination of food and food additives. Food additives serve the interests of both the consumer and the producer of foodstuffs since they inhibit the spoilage of food, thus reducing the losses and enabling greater production at a lower cost. They increase the viability of the diet, make preparation of food more convenient and help stabilize the quality of food. Many countries require a toxicological analysis of any food additive which determines, in most cases, the average amount of a substance expressed in mg/kg of body weight which can be taken daily in the diet over a lifetime without risk considering all known factors.
It should be noted that food flavouring substances are different from food additives as there are several thousand flavouring substances which occur naturally. Most flavouring substances are identical substances to the tens of thousands which have been detected in the flavouring component of natural foods such as fruits, spices, vegetables, milk and meat products. The natural flavouring component of foods is invariably an extremely complicated mixture comprising a few dozen to several thousand different chemicals of natural origin.