Cross-contamination happens when germs (or allergens) pass from one food, surface or person to another food. It is one of the most frequent causes of food poisoning, because the raw food is sometimes normally contaminated and what is dangerous is what it touches afterwards.
The routes of cross-contamination
- From food to food: raw chicken juice dripping onto a salad.
- Through utensils and surfaces: the same board or knife for raw meat and for bread or vegetables.
- Through hands: touching raw meat and then a ready-to-eat food without washing.
- Through cloths, dishcloths and sponges used for everything.
- Through air, water and waste: splashes, open bins, uncovered food.
- Through pests: insects and rodents.
Raw and ready-to-eat foods
Always keep apart:
- raw foods (meat, poultry, fish, eggs, vegetables with soil), which may carry germs;
- ready-to-eat foods (cooked food, salads, cured meats, cheeses, bread, desserts), which will not be cooked any further.
The main risk is a raw food contaminating one that is eaten uncooked.
How to prevent it
- Different areas or times. If there is no space, work with ready-to-eat food first and raw food afterwards, and clean and disinfect between the two.
- Separate utensils, boards and knives, for example by colour, according to your employer's system.
- Tidy fridges and cold rooms. Raw food at the bottom, covered and in closed containers, so that nothing drips. Cooked and ready-to-eat food on top.
- Food covered and labelled. Use cling film, lids or closed containers.
- Handwashing every time you change task.
- Wash fruit and vegetables that are eaten raw. If your employer says so, disinfect them with a food-safe product, following the dose.
- Do not wash raw poultry under the tap: splashes contaminate the surroundings.
- Single-use cloths or clean, dedicated cloths. Damp dishcloths are an ideal medium for germs.
- Manage waste well: bins with a pedal lid, emptied often, and never touched without washing your hands afterwards.
- Safe defrosting: in the fridge and in a container that catches the liquid, not at room temperature.
Cross-contamination with allergens
It is the same principle: residues of an allergen (milk, gluten, nuts…) passing to a dish that should not contain them. It is prevented with clean utensils, clean surfaces and tidiness. You will see this in the lesson on labelling and in the allergen course.
Goods: receiving and storage
- Inspect what arrives: broken packaging, dates, transport temperature and appearance.
- Reject what does not comply and tell your manager.
- Keep cleaning products away from food, in a separate cupboard and well labelled.
- Apply FIFO (first in, first out): the oldest is used first.
Key points
- Cross-contamination passes germs from raw food to food that is eaten uncooked.
- Separate in space or in time, use different utensils and clean between tasks.
- In the fridge, raw food always goes at the bottom and covered.
- Change gloves and wash your hands when you change task.