ONE is an inconspicuous spice used to add colour to a bland dish, the other is a preservative which many believe could be cancer causing.

But could you tell the difference between E100 and E251, or did you even know that the first is turmeric and the latter sodium nitrate?

And if you're a vegetarian would you know whether to avoid the red food colouring E120 because it may come from an animal origin or that E155, a chocolate brown food colouring, could cause an allergic reaction in asthmatics?

While consumers are becoming used to the E-numbers that pepper the ingredient labels on the back of food wrappers, few know what they are.

Campaigners last night called for clearer labelling of additives routinely used in food and drinks. The calls come after the consumer magazine Which? said ingredients on some food labels "read more like a chemistry experiment than something you would want to eat".

It believes a better system would give shoppers a clearer warning if they were anxious to avoid additives, which are routinely used to colour, flavour and texture, or to preserve food. Each must be approved by an expert panel which also sets safe intake levels.

But Which? said, "Despite the safety checks, there are still claims that some additives can lead to particular health problems.

"Some studies have shown a link between hyperactivity in children and certain flavourings and colourings, though findings aren't conclusive and other studies have found little or no effect."

Professor Denis Murphy, head of the biotechnology unit at the University of Glamorgan, said, "To the average shopper E numbers are meaningless - you have to get a reference book or spend hours on the internet to find out what a certain number is.

"Some E numbers may be colouring agents like saffron or preservatives we have used for hundreds of years without problems but others may be quite dodgy chemicals.

"But if we were given more information about each E number we would end up with huge labels bigger than the product itself.

"I am an informed consumer, I read the labels and make purchasing decisions based on that. But how many other people do and how many really care?"

Lindsey Kearton, senior policy officer at the Welsh Consumer Council, said, "The evidence shows that people struggle to understand the information on food labels and many feel they don't have the time or can be bothered to look at ingredient labels in depth.

"Quite often the information about additives is technical and people do not realise what they do.

"We would endorse clear, simple information on food labels to enable people to understand what they are buying."

Which? said that although additives were essential to provide safe, convenient food all year round, it questioned the need for E-number ingredients to make food more colourful.

The magazine adds, "We'd like to see one clear labelling system for additives to make it easier to avoid additives and to compare what's in different foods."

Additives: The breakdown

ADDITIVES are added to food to help its processing, production and to maintain or enhance the properties of food.

Emulsifiers, stabilisers, thickening agents and anti-caking agents all maintain the food's consistency.

Vitamins, minerals, and other nutrients are added to either maintain or improve the nutritional value of food.

Preservatives, antioxidants, and sequestrants help the to keep the food.

Natural and synthetic flavours and food colours are used to enhance the flavour and colour.

Food additives can be made synthetically or are derived from foods or other natural substances.

Food additives are regulated at the European Union by a directive which defines a food additive - except a colour or sweetener - as any substance with or without nutritional value.

Generally they are not consumed as food or a typical ingredient.

The use of a food additive is only allowed by approval of the EU Commission and only granted if it does not bear any risk to the consumer, if it is technologically necessary, and not intended to mislead the consumer.

E-numbers are assigned to each permitted food additive.