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Food spoilage.…read more

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Food spoilage
Food products can't be stored for a long time without changes taking place. The
changes that often occur are to the taste, texture and colour of the food.
Microorganisms and enzymes cause food spoilage and can cause food poisoning. The
three types of microorganism causing food spoilage are:
1. Bacteria
2. Yeasts
3. Moulds
Microorganisms are all around us, in the soil and air, on animals and humans and on
equipment and preparation surfaces in poor hygeine. The problem is, these
bacteria can't be seen without a microscope. However, a good thing about
microorganisms are that the can be used in the food industry to produce products
such as:
4. Cheese
5. Yoghurt
6. Bread
7. Quorn.…read more

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What conditions to bacteria need to
grow?
Temperature ­ Bacteria grows rapidly at 37 degrees c, however, growth occurs between the
temperature's 5 degrees c and 63 degrees c which is known as the danger zone.
Foods ­ Foods containing large amounts of protein and water (High risk foods) are the best
medium for bacterial growth.
Time ­ When in the right conditions, bacteria reproduce by dividing into two and this can
occur every ten to twenty minutes meaning that within a few hours, one bacterium can
become several million.
Moisture ­ Most foods contain moisture and so are ideal for maximum bacterial growth.…read more

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How does food poisoning happen?
Food poisoning occurs if harmful microorganisms contaminate food and are allowed to
grow. It's difficult to now if bacteria is present in foods as they don't actually affect the
appearance, taste or even the smell of the food. Bacteria that cause food poisoning are
called pathogenic bacteria. One example is clostridium botulinum. Pathogenic bacteria are
very harmful and can cause death in young children and the elderly. Poor hygiene during the
storage, preparation or serving of food can also result in food poisoning.
The main types of food poisoning bacteria are:
·Salmonella ­ This is the most common form of food poisoning in Britain. It's symptoms,
such as diarrhoea , vomiting, head aches and stomach pains appear 12to 36 hours after
consuming the affected food. Main sources of the bacteria are eggs and poultry.
·Campylobacter ­ This has symptoms such as diarrhoea and headaches and these occur
1 to 11 days after eating the food. Main sources of the bacteria are meat, poultry and
shellfish.
·Staphylococcus aureus ­ This is a bacteria that creates toxins which causes the food
poisoning. They are present in the nose, throat and skin of human beings and so can be
transferred to foods by poor personal hygiene. The symptoms that appear one to six
hours after consuming the food are vomiting, abdominal pain and diarrhoea. Main food
sources are meat, poultry and salads.…read more

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How can we stop bacteria from
growing in food?
If we make changes to any of the optimum conditions needed by bacteria for growth it
will stop them from reproducing or at least hopefully slow down the rate of
reproduction.
Temperature
From looking at the thermometer it can be seen that:
-18 degrees c ­ Bacteria are dormant and are unable to reproduce.
0 to 5 degrees c ­ Bacteria are `sleeping' and reproduce very slowly.
5 to 63 degrees c ­ Bacteria produce most actively. This is known as the danger zone.
37 degrees c ­ This is the optimum temperature for bacteria to reproduce.
72 degrees c ­ The bacteria start to get destroyed and are unable to reproduce.
Food ­ Bacteria grow best on high risk foods (foods that have a high protein and water
content).
Time ­ Food needs to be prepared as quickly as possible and should be chilled after
preparation as it should not be allowed to wait around in danger zone temperatures
before storing.
Moisture ­ Care must be taken when preparing food with a high moisture content.…read more

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Comments

jill richardson

A very useful presentation that is useful for all exam boards, not just AQA - although the last sentence should read 'checks not 'chicks'!

jim78787

uum

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