There is evidence that some additives cause allergic reactions and behavioural changes in susceptible people.

Additives serve a range of purposes from colouring food to regulating its acidity. Some perform more than one function. For example vitamin C (ascorbic acid) used to prevent tinned fruit from going brown along with improving the baking quality of wheat, while citric acid is widely used as both a Flavouring agent and as an acidity regulator.

Both processing and storage can result in food losing its natural colour so manufacturers re create it either to make the food look more attractive or because the consumers have come to expect foods to be certain colours.

In the Britain we like our butter to be bright yellow, the colour comes from beta-carotene, which is found in grass and animal feed and its intensity depends on the cow’s ability to metabolise the compound into vitamin A. The Jersey cattle do not efficiently metabolise beta carotene and produce much yellower butter than the Friesians, which do. UK manufactures of margarine and low fat spreads enhance the appearance of their products which otherwise would appear off white.

Among the more widely used colours, yellow tartrazine (E102) has been found to cause hyperactivity and other adverse reactions in a minority of consumers. Some doctors claim that tartrazine and other nitrogen-based azo dyes – many of which have been banned in Britain –can affect children’s behaviour, making them ill tempered and disobedient. Children with adverse reactions to these additives will often react to fruit or other natural foods which contain similar compounds.

When tinned or frozen foods deteriorate they can become toxic and, despite increasingly stringent regulations which cover the food processing industry, cases of botulism – a violent form of food poisoning – occasionally occurs. Preservatives slow down the deterioration of food – which should be eaten by the “best before” date.

As well as salt, vinegar, alcohol and spices, today’s food industry often relies on artificially produced forms naturally occurring benzoates. A few people have adverse reactions to benzoic acid; others are allergic to the sulphites and sulphur dioxides which are used to kill the yeasts that cause sugar fermentation in food and alcohol. Inhaling the sulphur dioxide, released when wines are opened and often very pungent, this may cause an asthma attack as can wine containing sulphur based additives. Organic acids, such acetic acid and propionic acid added to cereal products to prevent the formation of mould, are harmless. Sophisticated modern refrigeration techniques have helped to eliminate the need for some preservatives.