Transcript The causes of food deterioration

The causes of food deterioration
All food changes over time. These changes are not always
harmful s as hanging meat for flavour or mould in blue cheese.
Food does eventually become harmful or unpleasant to eat.
Milk going so, fruit becoming mouldy and meat becoming
putrid which can cause food poisoning. To preserve food the
enzymes and micro organisms have to be controlled.
Enzymes
Oxidation
Are chemical catalysts that are found in all
cells. They break down plant and
animal tissues causing fruit to ripen,
meat to tenderise and oxidation to
speed up. If the enzyme activity is
allowed to continue there is food
spoilage.
Enzymic browning takes place when fruit
and vegetables are exposed to air after
being cut. This causes the flesh to turn
brown. It can be prevented by adding
lemon juice to fruit salad. Blanching
vegetables before freezing and placing
vegetables/fruits in water until
needed.
Yeasts
 Are singled celled plants found in
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the air and on the skins of fruit.
Spoil the taste of food but don't
make it harmful
Grow on sugary foods.
Cannot grow at low temperatures
Cannot survive in sugar
concentration above 50%
Cannot survive in vinegar
Are destroyed by temperatures
above 70C
Moulds
Are a type of fungus. They....
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Settle on food and grow into a visible plant
which looks like fluff
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Grow on many foods including bread, cheese
and meat.
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Like slightly acid conditions
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Need moisture
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Need warm temperatures between 20C and 40C
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Are destroyed above 70C
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Can survive in the fridge but not the freezer.
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Mould on food means it is not very fresh and has
been badly stored .Some moulds can make you
sick or cause allergic reactions.
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Some moulds are used to give cheese its blue
veins and to make quorn
Bacteria
 Are single celled organisms
that are able to reproduce
rapidly.
 Sometimes harmless and
used in making cheese and
yoghurt such as probiotic
drinks which help digestion
 Sometimes harmful and
can cause food poisoning
and even death.
High and low risk foods
 Some foods are high risk. This
includes foods that are not cooked
before they are eaten.
 If food is contaminated by bacteria,
the bacteria will not be destroyed
before the food is eaten.
High risk foods
 Protein rich foods
 Cooked rice and lentils
 Moist foods like gravy
 Unpasteurised milk
Low Risk foods
Low risk foods are
 Fats and oils
 Foods with a high sugar
content
 High acid content foods
 Foods that are cooked
before you eat them
Making food safe to eat
In Food manufacturing
 Raw food is kept away
from cooked
 Workers dealing with raw
foods wear different colour
clothing.
 They have to walk through
sanitised baths to clean
their boots
Food poisoning bacteria
 Salmonella
 Found in raw meat, eggs,
sea food
 12-36 hours
 Symptoms include
diarrhoea, vomiting and
fever.
 May cause death in the
elderly and babies
Food poisoning bacteria
 E Coli
 Raw meat ,untreated water
and milk
 12-24 hours
 Symptoms include
diarrhoea, vomiting, blood
in diarrhoea
 Causes gastro enteritis in
humans
Food poisoning bacteria
 Listeria
 Soft cheese, pate and
unpasteurised milk.
 Causes symptoms like flu
 Can cause miscarriage or
premature labour.
 So possible carrier foods
should be avoided by
pregnant women.