This week I sat my food hygiene refresher at work. Thirty-five questions, a few drag-and-drop exercises and a lot of bacteria with long Latin names. It made me realise how much of this I do every day without thinking about it, so I turned my notes into a short course. Six lessons, about ten minutes, and a quick quiz at the end.
Whether you cook for a hospital ward or for your family on a Sunday, the rules are the same.
Lesson 1. How bacteria work
- Pathogenic bacteria are the harmful ones. They make you ill and you usually cannot see, smell or taste them.
- Spoilage bacteria make food go off. Unpleasant, but usually not what makes people sick.
- Toxins are poisons some bacteria produce. Many survive cooking, so killing the bacteria does not always make the food safe.
- Spores are a protective form some bacteria take. They survive cooking and wake up again when food cools slowly.
- In ideal conditions (warmth, moisture, food and time) bacteria can divide every 10 minutes. One bacterium can become millions in a few hours.
The danger zone is 5°C to 63°C. Keep cold food cold and hot food hot. A fridge only slows bacteria down, it does not stop them. In the freezer they become dormant, not dead, and wake up once the food thaws.
Lesson 2. Meet the usual suspects
| Bacteria | Where you find it | What to remember |
|---|---|---|
| Campylobacter | Raw poultry, unpasteurised milk | Most common cause of food poisoning in the UK. Bloody diarrhoea. |
| Salmonella | Raw chicken, eggs, animal intestines | Can cause every symptom of food poisoning. |
| E. coli O157 | Undercooked beef and burgers, cattle | As few as 10 bacteria can make you ill. Can damage the kidneys. |
| Staphylococcus aureus | Human nose, mouth, skin, cuts and boils | Fast, violent vomiting. Its toxin survives cooking. |
| Clostridium perfringens | Intestines, soil, dust | Soups, stews and gravies cooled too slowly. Forms spores. |
| Bacillus cereus | Rice, pasta, cornflour | The reheated rice bug. Vomiting and diarrhoea. |
| Listeria monocytogenes | Sandwiches, pâté, soft cheese, chilled ready-to-eat food | Grows even in the fridge. Symptoms can take 3 to 70 days. Dangerous in pregnancy. |
The people most at risk are the elderly, babies and young children, pregnant women and anyone who is already ill. That is exactly who I cook for on hospital wards, which is why none of this is optional.
Lesson 3. The numbers worth learning
| What | Temperature |
|---|---|
| Fridge | 0°C to 5°C (legal maximum for high-risk food in England, Wales and NI: 8°C) |
| Freezer | -18°C or colder |
| Cooking (core temperature) | 75°C |
| Hot holding | 63°C or above (a legal requirement) |
| Reheating | 75°C (82°C in Scotland) |
| Danger zone | 5°C to 63°C |
- Defrost frozen chicken in the fridge, on the bottom shelf, in a container. Never on the worktop.
- Cooling a large joint: cut it into smaller pieces and use a blast chiller. Never put hot food straight into the fridge.
- Why record temperatures? Not for the inspector. To catch a fridge or freezer that is failing before the food becomes unsafe.
Lesson 4. Storage and cross-contamination
- Raw meat goes on the bottom shelf so its juices cannot drip onto ready-to-eat food like ham or cheese.
- High-risk food lives in the fridge. Dried food (flour, rice, pasta) lives somewhere cool and dry.
- Use by is about safety. Once it has passed, the food is never used. Best before is only about quality.
- Use disposable paper towels or single-use cloths on surfaces. A reusable cloth just moves bacteria around.
- Empty the kitchen bins regularly throughout the day, never leave them overnight.
There are three kinds of contamination: biological (bacteria, from dirty hands or sneezing), physical (glass, hair, plastic, metal) and chemical (cleaning products such as bleach). And one distinction people often mix up: a detergent removes grease and dirt, a disinfectant reduces bacteria to a safe level. You need both.
Lesson 5. You are the biggest risk in the kitchen
- Wash your hands before work, after a break, between tasks and after handling raw food. Gloves do not replace hand washing.
- Dry them on paper towels. A damp towel is a home for bacteria.
- Cover cuts and boils with a blue waterproof plaster. Blue is easy to spot if it falls into food, and waterproof keeps Staphylococcus in.
- Protective clothing is there to protect the food from you, not your clothes from the food.
- A hair net stops a physical hazard (hair). It does not control bacteria.
Lesson 6. Pests, deliveries and the law
- The surest sign of mice is droppings. Also look for gnaw marks, greasy smears along walls and a musty smell.
- Delivery of bread with droppings on it? Do not bin it quietly. Report it to your manager and check the delivery lorry for infestation.
- HACCP (Hazard Analysis and Critical Control Points) exists for one reason: to minimise the risks from food hazards.
- Environmental Health Officers can enter a food business at any reasonable time and can close premises immediately if there is an imminent risk to health.
Test yourself
Ten quick questions. Click a question to see the answer.
1. Which bacteria is linked to reheated rice?
Bacillus cereus.
2. What is the danger zone?
5°C to 63°C.
3. What core temperature should food be cooked to?
75°C.
4. What happens to bacteria in the freezer?
They become dormant. They do not die.
5. Which bacteria can grow in the fridge?
Listeria monocytogenes.
6. Where does raw meat go in the fridge?
On the bottom shelf.
7. When can you use food past its use-by date?
Never.
8. Is broken glass a biological, physical or chemical hazard?
Physical.
9. Which bacteria lives on human skin and in the nose?
Staphylococcus aureus.
10. What is the most common cause of food poisoning in the UK?
Campylobacter.
Got all ten? Then you would have passed my refresher too. Questions about how we handle any of this in a real kitchen? Ask me.