Risk factors for food poisoning and how to prevent it
Outcome. FI: Henkilö tietää ruokamyrkytyksiin liittyvät riskitekijät ja osaa työssään ennaltaehkäistä ruokamyrkytyksiä. EN: The person knows the risk factors for food poisoning and can prevent it in their work.
Why it matters
Most food poisonings result from neglect of hygienic work practices. The danger is the ordinary mistake: food left out, hands unwashed, raw and cooked mixed up.
What to know
Typical causes are insufficient heating, slow cooling, wrong storage or transport temperature, contaminated raw materials, cross-contamination and an infected food worker. Raw meat and vegetables handled with the same tools or surfaces raise the risk.
Bacteria to know:
- Bacillus cereus: food prepared in advance, often the day before, and cooled too slowly.
- Clostridium perfringens: large batches cooled too slowly, such as at mass catering. Its spores survive boiling for 30 to 120 minutes. Leftover meat dishes are reheated to over +75 °C throughout.
- Staphylococcus aureus: carried on skin, nose, throat and hands; infected wounds raise the risk.
- Salmonella: raw or poorly cooked poultry and pork, unpasteurised milk, vegetables, cross-contamination. About 80 percent of Finnish infections are acquired abroad. Heating kills it: cook over +70 °C, poultry over +75 °C.
- EHEC: raw ground beef patties, so serve them fully cooked (+75 °C in the core at the thickest point, or +70 °C for two minutes), always for children. Raw mince and steak tartare are risky; raw mince must not be tasted. Heating kills EHEC, freezing does not.
- Listeria: multiplies in the fridge. Vacuum-packed cold-smoked and gravad fish and sliced cold cuts are typical risk foods. Heating throughout to about +72 °C destroys it. Hot-smoked fish is a risk only if contaminated after cooking. Vacuum-packed processed fish is stored at 0 to +3 °C.
- Norovirus: the most common identified cause of foodborne outbreaks in Finland, from infected kitchen workers and contaminated raw materials. Imported frozen berries are heated at +90 °C for at least five minutes, or boiled for two minutes. Oysters and shellfish can carry viruses when eaten uncooked.
Parasites: Trichinella occurs in wild boar, bear and fox and sometimes in pigs and horses. Freezing is not reliable for wild game. Anisakis simplex is a roundworm in North Sea fish such as herring, mackerel, cod and wild salmon. Fish eaten raw, or only marinated or salted, must first be frozen at -20 °C or colder for at least 24 hours, or -35 °C or colder for at least 15 hours. Fish heated to a core temperature of at least +60 °C for at least one minute needs no freezing. Baltic herring and sprat are outside the requirement.
If food poisoning is known or suspected, the operator notifies the municipal food control authority immediately, without waiting for laboratory confirmation, and keeps the suspected food or a sample for testing. The municipality investigates without delay with the communicable-disease authorities. A production kitchen should freeze a sample of about 200 to 300 g of each batch and keep it two to four weeks. Even one suspected botulism case is reported promptly.
Scenario
A caterer cooks a huge pot of stew on Thursday and cools it in the same pot overnight. By morning the centre is still warm, and guests fall ill after lunch. Portioning it into small trays and chilling to +6 °C within four hours would have prevented this.
Numbers to remember
| Item | Value |
|---|---|
| Cooking | over +70 °C throughout; poultry over +75 °C |
| Ground beef patty | core +75 °C, or +70 °C for 2 minutes |
| Reheating leftover meat | over +75 °C throughout |
| Listeria destroyed | about +72 °C throughout |
| Frozen berries | +90 °C for 5 minutes, or boil 2 minutes |
| Fish parasite freezing | -20 °C for 24 hours, or -35 °C for 15 hours |
| Fish heat treatment | +60 °C core for 1 minute |
| Sample kept | 200–300 g, 2 to 4 weeks |
Myth vs reality
- Myth: Freezing kills EHEC. Reality: Only heating does.
- Myth: Notify only after a laboratory confirms. Reality: Notify immediately on suspicion.
- Myth: Berries cannot carry viruses. Reality: Contaminated irrigation water can put norovirus and hepatitis A on them.
In the test
Cooking and reheating numbers and "notify immediately" appear often. "Only", "never" and "safe if fresh" are warning words.