Unit 2 of 10
Hazards and food contamination
Food is contaminated when it contains substances or micro-organisms that can spoil it or pose a health risk to whoever eats it. It can be contaminated without any change in its appearance, smell or taste.
Types of hazard
- Biological: bacteria (Salmonella, Listeria, E. coli…), viruses (norovirus, hepatitis A), parasites (anisakis) and moulds. They are the most frequent cause of food poisoning.
- Chemical: traces of cleaning products, pesticides, metals, degraded oils, undeclared allergens.
- Physical: glass, metal, bones, fish bones, hair, plastic, pieces of packaging.
How contamination happens
- At source: the food is already contaminated when it arrives (soil, water, animals).
- Cross-contamination: micro-organisms pass from one food, usually raw, to another that is ready to eat. It can be direct (contact between foods or dripping in the fridge) or indirect (hands, boards, knives, cloths, surfaces).
- Through the handler: dirty hands, coughing over food, wounds, street clothes.
What bacteria need to multiply
Nutrients, moisture, time and, above all, temperature. Between 5 °C and 65 °C (the “danger zone”) bacteria multiply quickly; in favourable conditions one bacterium can become millions in a few hours. Below 5 °C their growth slows down; above 65 °C they start to be destroyed.
High-risk foods
Meat and poultry, fish and shellfish, eggs and egg-based sauces, milk and dairy products, cooked dishes, cooked rice and pasta, sprouts and ready-to-eat products. With these, time and temperature control must be stricter than ever.
Golden rule: keep cold food cold and hot food hot. Food must not stay in the danger zone any longer than strictly necessary.