A food can be dangerous even if it looks normal. It may not smell bad or look bad and yet contain germs that make people ill. Knowing the hazards helps you avoid them.
The three types of hazard
- Biological: bacteria, viruses, parasites and moulds. They are the most common cause of food poisoning.
- Chemical: cleaning products, pesticides, metals from damaged utensils and undeclared allergens.
- Physical: objects that should not be in food, such as glass, pieces of metal, bones, jewellery or plasters.
Bacteria you should know
- Salmonella. It lives in eggs, poultry and meat. A classic cause is food made with raw or lightly cooked egg: homemade mayonnaise, sauces, a runny omelette, desserts that are not cooked. It causes diarrhoea, fever and vomiting.
- Listeria monocytogenes. It is special because it can multiply in the fridge. It turns up in soft cheeses, cured meats, smoked foods, pâtés and ready-to-eat dishes. It is especially dangerous for pregnant women, older people and people with weakened defences.
- Campylobacter. It is mainly linked to raw poultry. A very small amount is enough to make you ill.
- Staphylococcus aureus. It is found on the skin, in the nose and in infected wounds. If it gets into food, it produces a toxin that is not destroyed by cooking. That is why hand hygiene matters so much.
- Bacillus cereus and Clostridium perfringens. They form spores that survive cooking. They appear in rice, stews and sauces left at room temperature. They are prevented by cooling quickly.
- Shiga toxin-producing E. coli. It is linked to undercooked minced meat, unwashed vegetables and contaminated water.
Viruses
- Norovirus and hepatitis A virus. They are spread mainly by people who are ill (or have just recovered) and handle food with dirty hands. Also by shellfish from contaminated waters and by vegetables. Heat destroys them, but most disinfectants do not. Washing your hands and not working when ill is the key.
Anisakis
Anisakis is a parasite (a tiny larva) that lives in fish and cephalopods. If you eat it alive, it can cause pain, vomiting and allergic reactions.
- It is destroyed by cooking the fish until the whole product reaches 60 °C for at least one minute in the centre.
- It is also destroyed by freezing.
- Real Decreto 1021/2022 (article 8), which replaced the old Real Decreto 1420/2006, requires establishments that serve food (restaurants, bars, collective catering) to make sure that fish to be eaten raw or almost raw (carpaccio, ceviche, sushi, anchovies in vinegar, marinated and salted fish) has been frozen beforehand throughout the whole product: at −20 °C or below for at least 24 hours, or at −35 °C or below for at least 15 hours. These are the same values that Regulation (EC) 853/2004 sets for fish placed on the market.
- The establishment must inform customers that the fish has been frozen (or that it comes from Anisakis-free aquaculture), for example on the menu or with a sign.
- The rules provide for exceptions, for example for certain farmed fish. If you have doubts, ask your manager and insist on the supplier's guarantee.
- Anisakis is not removed by vinegar, lemon, salt or spices.
How germs grow
Bacteria need food, moisture, time and warmth. Between about 5 °C and 65 °C they multiply very quickly: this is the "danger zone". Controlling time and temperature is the most powerful tool you have. We will cover it in the temperatures lesson.
High-risk foods
These are foods eaten without further cooking and in which germs grow easily: cooked meats, cured meats, dairy, eggs, seafood, cooked rice and pasta, prepared salads, and sauces and desserts with cream or custard.
Key points
- Dangerous foods can look normal.
- Listeria grows in the fridge. Salmonella is linked to egg and poultry. Some toxins resist heat.
- Anisakis is prevented by cooking properly or by freezing beforehand (Real Decreto 1021/2022), not by lemon or vinegar.
- People mostly get ill because of poor temperature control, poor hygiene and cross-contamination.