Download Food Spoilage and Food Poisoning

Food Spoilage and Food
Poisoning
Food Spoilage
Natural Decay
Contaminated by microscopic forms of life
(micro-organisms)
Perishable Foods
Foods spoil rapidly due to:
Large amounts of water and nutrients
Examples include:
• milk
• fruit
• Meat
Natural Decay
Moisture Loss
• When water in the vegetable is not replaced
• Vegetable or fruit shrinks and becomes limp
• Skin becomes wrinkled and leathery
Natural Decay
Action of enzymes
Enzymes speed up the process of decay by breaking down
the foods tissues components creating:
• Oxidation – destruction of certain nutrients by enzymes in
food reacting with the air
• Browning – If apples are cut or bruised they will discolour
• Ripening - Enzymes involved in ripening of fruit (Banana Green – yellow - Brown)
Contamination by micro-organisms
The main micro-organisms are:
• Yeast
• Bacteria
• Moulds
Food is an ideal medium for micro-organisms as it
provides:
• nutrients –vitamins!
• moisture – water !
This helps the bacteria to survive
Friendly Bacteria
• Not all bacteria are harmful!
• Some are used in the food industry to
produce:
• Yoghurt
• Cheese
• Soy sauce
Food Poisoning
Bacteria
Bacteria are the most common form of food
Poisoning.
Symptoms include:
• Vomiting
• Diarrhoea
• Stomach cramps
What do bacteria need to survive?!
• Food
• Warmth
• Moisture
• Time
How does warmth effect the growth of
bacteria
• see Boardworks presentation KS4
Moisture
Bacteria need moisture to grow:
• Dried foods have a long shelf life as they do not
contain water.
In foods with
• high levels of sugar - jams
• High levels of salt - salami
• High levels of acid - pickles
Water is not available in the food to grow due to high
levels of salt sugar and vinegar
Foods that bacteria like
Bacteria prefer foods that are high in PROTEIN:
These are known as HIGH RISK FOODS
High risk foods include:
• Meat and poultry
• Eggs
• Fish
• Mayonnaise
• Dairy products
Bacteria multiplication
• Bacteria can multiply by splitting every 10-20
minutes
• In just 45 minutes one bacterium will have
multiplied to 1 million bacteria
Dangers of Food Poisoning
• Cross contamination
• Blood juices from raw food dripping onto
cooked food
• Bacteria being transferred from one food to
another on hands tools and equipment