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

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.

Oxidation

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 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….

Settle on food and grow into a visible plant which looks like fluff

Grow on many foods including bread, cheese and meat.

Like slightly acid conditions

Need moisture

Need warm temperatures between 20C and 40C

Are destroyed above 70C

Can survive in the fridge but not the freezer.

Mould on food means it is not very fresh and has been badly stored .Some moulds can make you sick or cause allergic reactions.

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.

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