There are three main causes of food spoilage: moisture loss, enzyme action, and microbial contamination. Moisture loss mainly affects fruits and vegetables after harvesting as they lose water through their skins. Enzymes cause foods to ripen and decay over time through processes like starch changing to sugar. Microbes like yeast, mold, and bacteria grow in foods at optimal temperatures and cause spoilage both on the surface and inside foods invisibly through toxin production. Proper food handling and storage can help control spoilage from these three causes to prevent food poisoning and ensure safety.

1. FOOD SPOILAGE
(c)PDST Home Economics

2. CAUSES OF FOOD SPOILAGE
• 1. Moisture loss
• 2. Enzyme action
• 3. Microbial contamination

3. 1. SPOILAGE BY MOISTURE
LOSS
• Mainly affects fruit and vegetables.
• After harvesting they can no longer get water from the
soil.
• Moisture is lost through skins and leaves.
• Causes wrinkling, shrinkage and limpness.

4. 2. ENZYME ACTION
• Ripening
Enzymes cause food to ripen, then become over-ripe and
eventually decay. Starch changes to sugar, colour
changes and texture softens.
• Browning
When certain foods are cut and the surface exposed to
air, enzymes cause them to turn brown. e.g. apples,
• Enzymatic rotting
Enzymes in fish cause deterioration even at low

5. CONTROLLING ENZYMATIC
SPOILAGE
• Inactivated by heating - cooking, canning.
• Cold temp slows action - cool storage.
• Enzymes in vegetables work at low temperatures so
they must be blanched before freezing.
• Acid inactivates enzymes - lemon juice used to stop
browning.
• Sulphur dioxide stops enzymatic spoilage.

6. 3. MICROBIAL
CONTAMINATION
• Yeast, mould and bacteria are the microbes that
cause food spoilage.
• Food at the optimum temperature is the ideal place
for microbes to grow.
• Yeast and mould spoil the outside of food and can be
seen.
• If the food is eaten it will probably be harmless,
unless they make mycotoxins.
• Bacteria cause spoilage by making toxins in food - not
visible.
• Souring bacteria spoil milk, yoghurt & cream.

7. FOOD POISONING
3 types
• 1.Chemical –Caused by pesticides, antibiotics, metals.
• 2.Biological – Caused by toxins naturally present in
food e.g. red kidney beans, green potatoes.
• 3.Bacterial - Caused by pathogenic bacteria in food

8. SYMPTOMS
• Abdominal cramps
• Nausea
• Vomiting
• Diarrhoea
• Fever
• Loss of appetite
Don’t eat for 24 hours. Drink cooled boiled water.

9. BACTERIAL FOOD
POISONING
2 types
• 1. Toxic
• 2. Infectious

10. (H) 1. TOXIC BACTERIAL FOOD
POISONING
• Caused by eating food containing toxins.
• Exotoxins are made by bacteria in the food before
and after it’s eaten.
• Exotoxins are difficult to destroy - must be boiled
for 30minutes.
• Symptoms develop quickly - within a few hours of
eating the food.

11. (H) 2. INFECTIOUS BACTERIAL
FOOD POISONING
• Caused by eating food containing large numbers of
pathogenic bacteria that produce endotoxins.
• The endotoxins are released when the bacteria die in your
intestine.
• Endotoxins are easily destroyed by normal
cooking/heating of food.
• Symptoms take longer to occur - over 12 hours.

12. (H) HIGH RISK FOODS
• Liquid protein foods.
• Milk, cream, eggs.
• Meat, poultry, fish.
• Meat dishes e.g. pies, gravies.
• Soups and stocks.
• Egg dishes e.g. custard, mayonnaise.
• Reheated dishes.