Food Contamination
What this domain covers
Contamination is any harmful substance or organism present in food that should not be there. Level-1 candidates must name the three hazard types, trace how contamination reaches food, and apply separation controls.
The three routes
- Biological: bacteria such as Salmonella, E. coli and Staphylococcus aureus; viruses such as norovirus and hepatitis A; moulds and their toxins; parasites.
- Chemical: cleaning and sanitising agents, pesticides, veterinary residues, heavy metals, unapproved dyes, and allergens transferred from another product.
- Physical: glass, metal fragments, stones, bone, packaging, plasters, hair and insects.
Cross-contamination
Direct transfer happens when raw food touches ready-to-eat food. Indirect transfer runs through hands, knives, boards, cloths, sponges, containers, drip from shelves, and pests. Controls: store raw meat below cooked and ready-to-eat food in the fridge; use colour-coded boards and cloths; wash hands between tasks; clean and sanitise surfaces between uses; cover food; keep waste away from preparation areas.
Worked example
A fridge holds a tray of raw chicken on the top shelf and an uncovered bowl of salad below. Nothing is touching. Is the salad at risk? Yes - Salmonella from the chicken can drip through the shelf onto the salad, and the salad will be eaten raw with no kill step. Moving the chicken to the bottom shelf and covering both items removes the risk.
Traps that cost marks
- Washing raw chicken under the tap, which spreads bacteria by splashing.
- Treating a wipe with a dirty cloth as “cleaning”.
- Assuming spicy, salty or acidic food is protected from contamination.
- Forgetting that allergens count as a chemical hazard.