What is cross-contamination?
Cross-contamination is the transfer of a harmful agent from one food, surface, piece of equipment or hand to another food. The classic example is using a board for raw chicken, then preparing a salad on it without washing it. Because salad is not cooked, nothing kills the bacteria that were transferred.
Types of cross-contamination
| Route | Example | Prevention |
|---|---|---|
| Food to food | Raw meat juices drip onto salad on a lower shelf | Raw items on the bottom shelf, in closed containers |
| Equipment to food | The same knife and board used for raw and cooked food | Separate equipment, or wash and sanitise |
| Hand to food | Plating after handling raw meat without washing hands | Wash hands when changing tasks |
| Allergen contact | Using the same container after a nut product | Dedicated equipment and a written procedure |
Cooking can reduce bacterial contamination, but it does not remove an allergen. That is why allergen control is its own topic. Use our free allergen matrix template for your kitchen.
What do chopping board colours mean?
Colour coding is most established in the UK. The table shows common usage. Colours can vary by source, and colour coding on its own is not a legal requirement; what matters is a written system that everyone knows.
| Colour | Common use |
|---|---|
| Red | Raw meat and poultry |
| Blue | Raw fish and seafood |
| Yellow | Cooked meat |
| Green | Salad and fruit |
| Brown | Unwashed and root vegetables |
| White | Dairy and bakery (varies by kitchen) |
| Purple | Allergen-free preparation |
Colour alone does not protect you: boards still need washing between uses.
How do you prevent cross-contamination?
Storage
- 1In the refrigerator, top to bottom: ready-to-eat food, cooked food, vegetables, fish, raw meat, raw poultry.
- 2Keep raw items in closed containers. Follow FIFO and label everything.
Preparation
- 3Use separate boards, knives and gloves for raw and ready-to-eat food; separate the area too if you can.
- 4Do not wash raw meat: splashing spreads bacteria around.
- 5Wash hands with soap when changing tasks. Gloves do not replace handwashing.
Cleaning
- 6Clean first, then sanitise. Dirt stops a sanitiser from working.
- 7Keep cloths separate and change them often.
Service
- 8Never put cooked food back on a tray or plate that held raw meat.
- 9Pass allergen orders from service to kitchen in writing.
Kitchen checklist
| Check | Frequency |
|---|---|
| Refrigerator shelf order | Every shift |
| Board and knife separation | Every shift |
| Handwash sink and soap | Every shift |
| Temperature log | Every shift |
| Allergen equipment and labels | Weekly |
| Team refresher training | Periodic |
For temperatures, see the food danger zone chart; for systems, see what HACCP is. To build this routine in your team, take a look at our kitchen team training.
