• Causes of food spoilage • Types of food poisoning • Common symptoms of food poisoning • Groups vulnerable to food poisoning • Profiles of infectious food-poisoning bacteria • Profiles of toxic food-poisoning bacteria
FOOD SPOILAGE
Food naturally goes through a cycle of decay that eventually results in spoilage. The rate of food spoilage is quicker among perishable foods, e.g. milk and bread. When food is spoiled it becomes inedible.
Causes of food spoilage The main causes of food spoilage are enzyme action, moisture loss and microbial contamination.
Enzyme action
Enzymes are protein catalysts that speed up chemical reactions without being destroyed or changed. They are naturally present in food and play a role in food spoilage, as they bring about: • ripening of food
• browning of food (enzymic browning)
This type of spoilage is known as enzymic spoilage. Ripening of food
All fruit and vegetables naturally contain enzymes responsible for their ripening. As enzymes ripen the:
• taste (sweetness) improves, as the high starch content is converted to sugars, e.g. fructose • colour changes, e.g. tomatoes change from green to red
• texture changes, e.g. hard bananas become soft and easy to digest.
Enzymes continue to work after ripening, and eventually cause fruit and vegetables to become overripe and then to decay and decompose.
222 Complete Home Economics • enzymic deterioration.
