Ever Wondered About... Food additives?

Are the additives in foods giving us more than just a longer shelf life and distinctive flavour?

By: The OpenLearn team (Programme and web teams)

  • Duration 10 mins
  • Updated Wednesday 27th April 2005
  • Introductory level
  • Posted under Chemistry
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Did you know? Some of the food additives we use today have been used for more than 2000 years.

Ever wondered what life would be like if there weren’t any food additives? If you’re thinking "great" then think again. Without additives, many foods we take for granted just wouldn’t be there. Without preservatives, food would quickly become riddled with the poisonous chemicals of decay. Without raising agents, even something as basic as bread would fall flat. Most food additives are harmless, natural substances. Even so, people worry, and justifiably so. There are three possible scientific mechanisms by which a chemical might cause harm. It could cause allergies; if consumed in large enough quantities it could be toxic; and under certain biochemical conditions it could cause cancer.

Did you know…? The colouring N,N-dimethyl-4-amino-azobenzene (butter yellow) was withdrawn because of its carcinogenic effects.

History of additives

Once upon a time everybody worked the land and there wasn’t any need for food additives – people just ate what they could grow. But it wasn’t a very varied diet. Once people started living in cities, food had to be grown for them, and to survive transportation. With the Industrial Revolution the cities burgeoned, and farmers had to provide for increasing numbers of urban workers. Today, we can get hold of an extraordinary range of exotic foods from farmers all over the world, partly or fully prepared to save us time. But concerns about food’s additives, production and distribution, not to mention its environmental impact, may be the price we pay for our 21st century lifestyle.

Did you know? The ancient Greeks burned sulphur over wine casks before sealing, to produce the preservative sulphur dioxide, which is used to this day.

A food additive is any chemical, natural or man-made, which is not normally consumed as a food in itself but is added to foods to perform certain functions. In Europe there is a classified listing of substances which manufacturers are permitted to use - the so-called 'E' numbers.

  • Colourings: to make the food look attractive.
  • Preservatives: to check or prevent the growth of micro-organisms.
  • Anti-oxidants: to stop food from reacting with oxygen in the air.
  • Emulsifiers: to stop oil and water-based ingredients from separating out.
  • Sweeteners: no prizes for guessing this one!
  • Flavourings: no prizes for guessing this either!
  • Chelating agents: to trap metal atoms that would otherwise discolour or degrade food.
  • Flavour enhancers: to accentuate the natural flavour of foods.
  • Thickening agents: to absorb water and stabilise factory-made sauces etc.
  • Solvents: to act as a vehicle to dissolve other ingredients.
  • Stabilisers: similar to emulsifiers and thickeners, stop droplets colliding with each other.

Did you know…? Without colourings, margarine would be grey.

Additives and allergies

If you’re allergic to pollen or aspirin, it’s possible you might also be sensitive to one of the additives used in food. Allergies occur when the body’s immune system fires off against an otherwise harmless chemical in the environment or in food. The symptoms include skin rashes, difficulty with breathing, runny noses, gastro-intestinal problems, even life-threatening anaphylaxis. But it’s not just additives that can cause them. In fact, most food allergies are provoked by chemicals which occur quite naturally in foods (eg: peanut allergy).

Did you know? Some lemon squashes contain sodium metabisulphite (E223), which can cause allergies in susceptible people and should be avoided by asthmatics.

Additives and toxicity

"It is the dose that makes the poison" (Paracelsus, 16th century polymath)

In order to get onto the European list of permitted additives (to become an E number), a chemical has to undergo a number of toxicological tests. So it’s very unlikely that an additive will actually poison you. Mass poisonings in the past have usually been due to chemicals which got into the food chain accidentally, not by design. That doesn’t mean the chemicals used as additives don't have any toxic effects – you’re just not going to consume them in anything like the doses needed for toxicity to show. However, there are some scientific mechanisms by which food additives, or their metabolic products, could cause sub-clinical effects.

Did you know? Some kinds of bacon contain nitrite which can interfere with the red blood cells’ ability to carry oxygen.

Doses

Whether it’s cyanide, dodgy mushrooms or food additives, the same toxicological principles hold true. If a chemical has any toxicity, the extent to which it shows depends on several factors. Firstly, you have to consume the chemical in high enough doses to cause damage (a single molecule of cyanide never did anyone any harm). Then there’s the length of time you consume it over (six cans of fizzy pop in one sitting could be trouble). There are differences due to age, sex and species (just because something’s safe for laboratory rats, it may not be safe for humans). And finally there can be environmental effects, which may aggravate or mitigate toxicity.

Did you know? Even water can be toxic if you drink enough of it.

Scientific mechanisms of toxicity

It’s a myth that all chemicals are toxic – in fact many pass straight through you without any ill effects. But when known poisons do work their evil ways, they do so through several distinct biological mechanisms. Some poisons stop ions like calcium from getting in and out of cells. Others interfere with our ability to get energy from food. Others compete with the chemicals our bodies need, like oxygen. Yet others deactivate the proteins and nucleic acids that are crucial to the day-to-day running of our bodies. And if it’s DNA they happen to attack, they could cause cancer.

Did you know? Food additives in Europe must adhere to twenty EC directives.

Additives and Cancer

How can a chemical cause cancer? The answer lies in simple organic chemistry. The behaviour of molecules is the result of a balancing act between positive and negative charges. Basically, the reactive forms of many cancer-causing agents (carcinogens) are positively charged, so they behave as though they are seeking a negative charge (electrons) to redress the balance. DNA on the other hand behaves as if it wants to hand over a few electrons. In this way, the carcinogen may seek to share some of the DNA's electrons by forming something called a covalent bond with the DNA. This can alter the entire 3-dimensional structure of the DNA. If it doesn't get mended, when it replicates, mistakes or mutations can happen.

Did you know? Some fizzy drinks contain saccharin which is a suspected carcinogen (but you would have to drink many tens of cans per day to even approach the toxic dose!).

Carcinogens

Even when the chemicals that get into our body aren’t cancer causing (carcinogenic) in themselves, they may become so when they’re broken down by the body. Food additives are only a minor source of such chemicals. Others come from the actual food itself, drugs, cigarettes, and contaminants in the food and the environment. In fact, the body is literally swimming in potential carcinogens. It’s also made up of millions of cells, each one of which has DNA which could be affected. So the real surprise is why cancer doesn’t happen more often. The answer lies in the body’s amazingly sophisticated DNA repair mechanisms.

What's in...

Sausages

  • Water - acts as a solvent
  • Rusk - absorbs fat and water
  • Salt - preservative agent
  • Protein concentrate - for creating emulsions
  • Polyphosphate - synergistic with salt - increases emulsifying properties
  • Monosodium glutamate – a flavour enhancer, highlights savoury taste
  • Cochineal - colouring agent (may exacerbate hyperactivity in susceptible children)
  • Sodium metabisuphate - suppresses food poisoning organisms
  • Sugar - caramelises when heated to give brown colour
  • Ascorbic acid - vitamin C, anti-oxidant, stops loss of flavours particularly when frozen

Ice-cream

  • Air -­ gives a light texture
  • Mono and diglycerides of fatty acids - act as emulsifiers
  • Soya lecithins -­ emulsifier and viscosity reducer in chocolate
  • Carageenan - ­ emulsifier (may degrade to potentially carcinogenic products)
  • Carob bean gum -­ gelling agent and stabiliser Guar Gum ­ thickening agent (in huge quantities may cause nausea etc)
  • Carboxymethylcellulose - thickening agent, stops loss of moisture
  • Sodium alginate -­ acts as a stabiliser Vanilla extract ­ gives flavour
  • Annatto -­ colouring agent, precursor to vitamin A
  • Curcumin - colouring agent
  • Pectin - emulsifier, stabiliser and gelling agent extracted from fruit