Food processing

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Affecting natural resources
The food production chain


The BBC – The history of canning
Guide to home canning
Dirty secrets of the industry

Chemical Heritage Magazine

Food science & the modern meal. A video and three stories each with its own defining moment in the 1910s.


Grilling and the barbecue


The biggest worldwide producer of tomatoes is China, followed by the USA, Turkey, India and Egypt.

Nutrition: Tomato Factsheet


Timeline of food processing
Chemical make up of alcohol
What processing does to bread
Chemicals in fast food
Food scandals in Europe
Brief history of the spud
Home grown tomatoes
MSG in your Chinese food

Genetically Modified Organisms

The debate on Genetically Modified foodstuffs

The GMO world map (Infg)


Increasing pressure on natural resources

By 2050 the world population is expected to rise by a third. Diets have changed to more meat and dairy. This is placing an increasing global demand for food, land, energy and water. Agriculture also is competing for resources as urbanisation and industrialisation put more pressure on land.

The production of more food with less land is the issue the food industry is facing. This is one reason GM hs been rapidly introduced, and for this same reason why we shall finally see the widespread use of cloning to feed the human race.

This section is about the preparation and processing of our food.

Nutrient loss in processing

Nearly every food preparation process reduces the amount of nutrients in food. In particular, processes that expose foods to high levels of heat, light, and/or oxygen cause the greatest nutrient loss. Nutrients can also be washed out of foods by fluids that are introduced during a cooking process. For example, boiling a potato can cause much of the potato’s B and C vitamins to migrate to the boiling water. You’ll still benefit from those nutrients if you consume the liquid (i.e. if the potato and water are being turned into potato soup), but not if you throw away the liquid. Similar losses also occur when you broil, roast, or fry in oil.

The table compares the typical maximum nutrient losses for common food processing methods. This table is included as a general guide only. Actual losses will depend on many different factors, including type of food and cooking time and temperature.

Source information: SelfNutritionData


The term ‘processing’ send shivers up most people who take an interest in a healthy lifestyle. However it is simply a word and most food has to go through a process of preparation and packaging of some sort.

Processing can involve canning and this is what sometimes is the cause of health concerns. This is because canning undergoes a stage of heating which tends to degrade the goodness in terms of nutrients.

In 1795 the French military offered a cash prize of 12,000 francs for a new method to preserve food. Nicolas Appert suggested canning, and the process was first proven in 1806 in tests conducted by the French navy. Appert was awarded the prize in 1810 by Count Montelivert, a French minister of the interior.

Since around 1825 canning food has been the preferred method of storing food. Canning keeps the food readily accessible for extremely long periods of time, usually up to five years.

Think about soldiers far away from home at war in years gone by, canned food and dried biscuits is what sustained them. Think of a few tins in the larder as a backup in case you suddenly find yourself with nothing fresh to eat indoors. There’s no doubt canning food was one of the single most beneficial discoveries in the history of our food processing.

In canning, you boil the food in the can to kill all the bacteria and seal the can (either before or while the food is boiling) to prevent any new bacteria from getting in. Since the food in the can is completely sterile, it does not spoil.

Canning isn’t just food in cans, it can be glass jars, sealable containers, plastics, any container that can be boiled and sealed. A number of methods are used: Milk is pasteurised in a box (UHT) and like a can it can be kept at room temperature until needed.

When the can is opened, bacteria immediately starts to effect the food so refrigeration helps to slow this process until we are ready to consume the food.

As well as losing nutrients when food is at the heating stage, the other disadvantage of canning is that the process of boiling changes the taste and texture of food and this is the main reason freezing and refrigeration are prefered.

Unfortunately there is no get out of having to boil certain types of food at high temperature. Items that measure below 4.6 on the pH scale (potential of hydrogen), require sterilisation at a temperature between 116 – 130 °C.

The microorganism Clostridium botulinum (which causes botulism), can only be eliminated at temperatures above the boiling point. To achieve this requires the use of a pressure canner. Foods that are low in acidity include most vegetables, meat, seafood, poultry and dairy products.

Foods that can be safely canned without high temperature are highly acidic ones with a pH value below 4.6. These include fruit, pickled vegetables, or other foods to which acidic additives have been added. Although pressure canners may also be used for processing acid foods, boiling water canners are recommended for this purpose because they are faster.

Nicolas Appert c1750 – 1841

Nicolas Appert was a chef, confectioner and distiller in the town of Chalons-sur-Marne when the French Revolution broke out.

The principle that Appert discovered was that food such as soups, fruits, jams or stews could be prevented from decomposing it they were first sealed inside a bottle or jar and then immersed in boiling water for several hours. He had to exclude all air and hold the jar tightly closed with cork, wire and sealing wax for this to work properly.

The next steps in canning

Due to the fragile nature of glass, in 1810 Peter Durand used an iron container covered with a thin plating of tin and the tin can was created and patented by him. By 1813 Durand was supplying the Royal Navy with canned meat. By 1818 this was as much as 24,000 large cans.

At this time the Royal Navy had faced an age old problem of scurvy on long voyages. During those times live cattle and other fresh provisions as well as salted meats were taken onboard for voyages and salt was a way of preserving cold meats.

They understood scurvy to be related to food and in particular to salt in some way. Salt actually was the problem in that meats lose most of their nutrients during the salt-cured preservation process. Scurvy is the result of a vitamin C deficiancy, as this was unklnown at the time canning presented the answer to voyage foods.

Cans needed to be heated for around five hours to fully sterilise the contents. In 1860 it was found that adding calcium chloride to the boiling water made it possible to raise the temperature and canning bacame faster.


Food should be frozen as soon after harvest as possible and at their peak degree of ripeness. From the moment fruit and vegetables are harvested enzymes begin their work hell bent of the demise of their host.

These chemical compounds cause the loss of colour and nutrients in the food and they must be inactivated. This is done by blanching vegetables, this is why chefs plunge their green veggies in boiling water briefly so that the colour remains bright and appetising.

You can’t blanche fruit, but something needs to be done as they will lose vitamin C rapidly and some fruits turn quicker than others. So a chemical is used, ascorbic acid, which is vitamin C.

There are some other methods used but none as effective as ascorbic acid to prevent browing of the fruit.

The freezing of fruit is fairly easy as fruit is made up of 90% water. The problem is that water expends when frozen and as 90% of the fruit cells contain water, they pressurize and can even rupture the cells walls. When the fruit is thawed the texture is much softer, tomatoes for example go mushy.

An industrial method to cope with this is to rapid freeze. This method forms different crystals and reduces the pressure on the cell walls. At home, packing your freezer will mean a slow freezing process and therefore will result in a poorer quality product when defrosted. Build the items up over time in your freezer.

The freezing process does not actually destroy the microorganisms which may be present on fruits and vegetables. While blanching destroys some microorganisms and there is a gradual decline in the number of these microorganisms during freezer storage, sufficient populations are still present to multiply in numbers and cause spoilage of the product when it thaws.

Freezing, when properly done, is the method of food preservation which may potentially preserve the greatest quantity of nutrients. To maintain top nutritional quality in frozen fruits and vegetables.


Q: Will food spoil if it stays frozen longer than the recommended storage time?

A: No.

This is a quality versus a food safety issue. Recommended storage times insure maximum quality. Food stored longer will be safe to eat but you may notice changes in flavor, color and texture. For best quality, use frozen fruits and vegetables within 8 to 12 months.



By Marilyn Herman, Extension Educator — Food Safety Reviewed 2014 by Deb Botzek-Linn, Extension Educator — Food Safety. Source article: University of Minnesota

Vinegar is the preservative and flavouring agent in most pickles. What kind you use depends on the color and flavour you want to have in the pickled product.

Most pickle recipes call for distilled white vinegar. This is the clear, colorless vinegar made by fermenting grains. It has a mellow aroma, tart acid flavor, and does not affect the color of the light-colored vegetables or fruits.

Apple cider vinegar, made from fermented apple juice is a good choice for many pickles. It has a mellow, fruity flavour that blends well with spices. However, it will darken most vegetables and fruits. Apple cider-flavour distilled vinegar has the flavour and brown color of apple cider vinegar, but it is a mixture of apple cider flavouring and distilled vinegar. Use it in the same way as apple cider vinegar.

These three vinegars contain five percent acetic acid. Occasionally you will find four percent acetic acid vinegar. This is salad vinegar and not strong enough to make a good quality pickles that will be heat processed.

Do not use wine vinegars or other flavoured vinegars when you make pickles, unless you are sure of their acetic acid content. Do not use homemade vinegar when you make pickles because the acetic acid content is unknown and variable.

When you make pickles, do not dilute the vinegar unless the recipe specifically directs you to add water to a 5% strength vinegar. If the flavor seems too tart, add a little sugar. Old family recipes for pickles were based on 10% strength vinegar and substituting 5% strength vinegar will lead to soft and poorly flavoured pickles.

The name vinegar comes to us from the French, who aptly named it “vin aigre,” literally meaning sour wine. A cask of wine that went bad turned out to be a wonderful new product.

For further information on freezing, canning, drying and pickling see the following websites:

University of Minnesota
Misconceptions About Vinegar’s Health Benefits
The Vinegar Institute