Page last updated at 11:33 GMT, Wednesday, 21 October 2009 12:33 UK

The secrets behind our processed food

Jimmy Doherty with home-made 'supermarket' food
How much of the food in your supermarket trolley could you make at home?

The organic, home-made food trend may have grown rapidly in the past decade, but in the recession many have returned to cheaper, processed produce. Yet few of us know how such everyday foods are made.

Supermarkets are among the relative handful of businesses to have prospered during the recession, as others have struggled to stay afloat.

Jimmy's Food Factory starts on Wednesday 21 October on BBC One at 1930 BST

As household budgets have been cut, shoppers have been seeking out bargains in preference to pricey alternatives. For example, sales of organic vegetables slumped 19% in the past year.

But if the British palate has been readjusting to cheaper, often processed foods, few shoppers know much about how such produce is created. Suffolk-based farmer Jimmy Doherty has been working to overcome this consumer blind spot, finding out for a new BBC TV series how science and ingenuity combine to produce good quality food on such a mass scale.

So, what are the processes some of the most common convenience foods go through before they reach our supermarket trolleys?


Taking maize and making it into flakes is quite a complicated process.

Jimmy attempts to make his own cornflakes

The dried corn kernel contains a tiny germ, the seed. The outer layer is the bran, which is removed, as it would spoil the cornflake's texture. The germ, containing the vitamins and proteins, is also removed, because over time the oils will go rancid and spoil the flakes.

What remains is starchy, hard material, or corn grits.

In the factory the grits are heated under very high pressure for 90 minutes, and then spun in huge driers to get rid of the water.

At this point cornflake manufacturers add six different B vitamins, as well as salt and sugar for flavouring and iron - in the form of food-grade iron filings. Giant rollers then squash the softened grits into flakes, ready to be toasted.

Cornflakes were originally invented by John Harvey Kellogg, an American doctor. The legend goes that one day Dr Kellogg accidentally overcooked a batch of corn.

Not wanting to throw them out, he processed the corn anyway, but instead of forming into the desired dough sheets, the corn formed into flakes, and received a good response from the patients at his health spa.


White sugar lasts forever, unless it gets wet. It is 99.9% pure sucrose, refined and processed into small crystals.


Chopped Beet
The sugar beet is sliced into chips and stewed in hot water, producing a cloudy yellow liquid.
Lime Solution
In a process called carbonation, carbon dioxide gas and a solution of the mineral lime purify the liquid.
Filtering Liquid
The lime and carbon dioxide create chalk - as the chalk is filtered from the liquid it traps any impurities.
Boiling Beet
The liquid is put in a large evaporator, to produce a thick syrup which is then boiled.
Spinning Sugar
When spun at the right temperature and a high centrifuge the syrup becomes sugar crystals.
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More than half the sugar we consume in the UK comes from the home-grown sugar beet. But beet only contains 17% sugar, and a very precise chemical process is used to produce the sparkling white sugar you might sprinkle on your cornflakes in the morning.

The beet is chopped and stewed in hot water for about an hour, which produces a yellow, cloudy liquid, a bit like tea.

The impurities are removed from the liquid by a process known as carbonatation, which uses carbon dioxide gas and a lime solution.

When carbon dioxide is added to lime, calcium carbonate or chalk forms, trapping the impurities. When the chalk is filtered out, the sugar juice is much purer but still very diluted.

To turn the liquid into sugar crystals, the juice is put in an evaporator and then boiled - this leaves behind a thick syrup. If the temperature is exactly right and the syrup is spun in a centrifuge, the syrup starts to separate from the crystals, leaving pure white sugar. This is then dried and ready for bagging.


Instant coffee is simply brewed coffee with the water removed. There are two methods for producing instant coffee crystals - freeze-drying and spray-drying.

Jimmy takes on the challenge of spray-drying instant coffee

The freeze-drying method preserves the most flavour but is a more complicated process.

First, the coffee is allowed to sit so the water evaporates naturally, leaving a concentrated coffee solution.

This concentrate is then frozen to around -40 C. The remaining water freezes into ice crystals. Sublimation is used to remove the ice. What is left is dry grains of coffee.

The second method is spray-drying. The water is again allowed to evaporate, forming a concentrate.

The concentrated coffee is sprayed from a high tower in a large hot-air chamber. As the droplets fall, the remaining water evaporates. Dry crystals of coffee fall to the bottom of the chamber. The high temperatures involved in this method can affect the oils of the coffee and the resulting flavour.

Instant coffee was developed in 1906 by George C Washington - an Englishman living in Guatemala and a chemist by trade. He noticed a powdery build-up on the spout of his favourite silver coffee pot. After some experimentation he created the first mass-produced instant coffee.


Processed cheese is made of a blend of around 60% natural cheese chopped up into tiny bits.

Water is then added to the mixture, sometimes along with milk solids and other flavourings like ham or onion.

Jimmy tries processing normal cheese

Then emulsifying salts (such as phosphates or sulphates) are added - these ensure that the fats in cheese will not separate when the product is heated, as happens with natural cheese.

Then the mixture is pasteurised, killing any living organisms which would cause the cheese to mature or further develop in flavour.

Finally, the mixture is melted and mixed together to make a homogeneous emulsion which can be extruded into sheets, poured into moulds, or, with extra water added, packed into jars as a sauce.

Processed cheese may have a reputation as being bland and rubbery, but it is stable when heated and has a long shelf life - making it useful for fast-food burger restaurants, for example.


How do salad producers make sure there are no bugs or caterpillars in bagged salad? Jimmy Doherty visited a salad producer in Wiltshire which tries to minimise the use of chemicals or pesticides. Providing a million and a half bags of salad a week to supermarkets, it uses sticky flags and bat boxes, and sows wild flower seeds to encourage aphid predators like ladybirds.


Fly Flags
As soon as the seed is sown, sticky flags trap marauding insects and minimise pesticide use.
Salad Harvester
When the crop is ready the clanking chains of the harvester shake the leaves and frighten off bugs.
Cold Leaves
Within an hour of harvest the leaves are stored at 1C at the packing plant to keep them from wilting.
Optical Sorter
The leaves go through an optical sorter and any defect leaf or insect is blasted off the conveyer belt.
Salad Washed
The leaves are washed in spring water then spun, weighed and bagged, ready for the supermarket.
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When the salad crop is ready for bagging, clanking chains on the harvester machine are designed to shake off insects as it moves down the row of plants. A bouncing belt transports the leaves up into the machine, and has holes small enough for insects to fall through.

To keep the leaves from wilting they are stored at 1C as soon as they reach the packing plant, within an hour of being harvested.

As they are unloaded they are put through an optical sorter machine which uses state of the art cameras and software equipment to photograph the leaves 4,000 times a second.

The images are fed into a computer system, which identifies any insects or defects on the leaves. If it spots a problem it sends a blast of air to the right spot on the conveying belt, and ejects the defective leaf.

Bagged salad got a bad reputation when it was revealed that some producers wash it in mild bleach. But at the Wiltshire plant the leaves are washed in a bath of spring water. A mesh wheel pushes the leaf underwater and any buoyant insects are separated. Finally the leaves are spun to get rid of surplus water, weighed and bagged - ready for the supermarket.

Here is a selection of your comments.

Karl, everybody has the ability to put together a salad - just open a bag, cut up some other ingredients and add some beans and/or protein. It is not difficult nor requires masses of equipment. I lived very happily with a camping stove's one ring burner for six months while our kitchen was being replaced and it never crossed our minds to get a takeaway.
Rebecca Portsmouth, London

In France you can buy unwashed, untreated salad. It may contain the odd bug as well as mud, there is a little more waste, less shelf life, but it is much healthier, crisper and a fraction of the price.
M Jordan, London, UK

Great examples of how the food industry has gone mad. Farmers only get 9p in every £1 spent on food in a supermarket, Milk is cheaper than water in some shops, crazy. We need to go back to basics and buy real food direct from the producer or local retailer who has sourced locally. We will save money by cutting all the middle men, keep our money in our area and encourage local farmers to grow a wider range of produce.
Anthony Davison, Huntingdon

To Julie, you have it backwards. Its not widely available in the supermarkets anymore because sales fell so dramatically. When supermarkets don't shift enough of a fresh product they just stop ordering it, as it would be a huge waste of money to have it in the shop to simply throw it away.
Joe, Manchester

Katie, the live snail in your salad is a good sign that the grower was minimising the amount of pesticides used. You can always pick it off and wash the leaves. Try growing a lettuce in your garden without getting any pests on it. It is not easy.
Chris, England

I found a real live little snail with wiggly antenna in a bag of salad I bought earlier this year. I haven't bought one since it was such a traumatic experience.
Katie MacDonald, Skye

I would love to buy more organic vegetables and meat, but the selection available in the local supermarkets has dropped dramatically over recent months. Of course sales have fallen if the products aren't available to buy.
Julie, Bridgnorth

It can be easy to forget that not everybody has adequate facilities at home to prepare a salad or cook a meal; I was talking about takeaways recently and someone pointed out that many people living in bedsits or hostels don't have these facilities.
Karl Chads, London, UK

Your sugar production process misses out the very essential crystallisation step in the vacuum pans between the boiling and the centrifuge. The centrifuge only separates the crystals from the mother liquor; it does not crystallise the sugar and is not temperature controlled.
Paul, Leeds

Processed cheese "has a long shelf life - making it useful for fast-food burger restaurants, for example." Isn't that a contradiction?
Hensley Seagle, Cambridge

I suspect Jimmy didn't add the E numbers to the processed cheese mix, yellow colour, and things to enhance the flavour. Should have passed it through the mangle to get it thinner.
Colin Bartlett, Oxford

The only processed food I eat is wholemeal bread, everything else comes as nature intended. Either in its skin ,or as a whole food, and when in season preferably.
Al W

I will consume my rocket salad with a deeper appreciation this lunchtime.
Candace, New Jersey, US

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