Cross-contamination occurs when bacteria are transferred from one place to another. This is usually from contaminated food( usually raw food), equipment or surfaces to ready to eat food. It is the cause of significant amounts of food poisoning and care must be taken to avoid it.
Cross-contamination could be caused by:
- foods touching, eg. raw and cooked meat
- raw meat or poultry dripping onto high-risk foods
- soil from dirty vegetables coming into contact with high-risk foods
- dirty clothes, dirty staff uniforms or dirty equipment
- equipment used for raw than cooked food r.g. chopping boards or knives
- hands touching raw than cooked food, not washing hands between tasks, etc.
- pests spreading bacteria around the kitchen
Separate working areas and storage areas for raw and high-risk foods are strongly recommended. If this is not possible keep them well away from each other and make sure that working areas are thoroughly cleaned and disinfected between tasks.
Vegetables should be washed before preparation/peeling and again afterward. Leafy vegetables may need to be washed in several changes of cold water to remove all of the soil present.
Good personal hygiene practices by staff, especially frequent and effective hand washing is important in controlling cross-contamination and will avoid the significant amounts of contamination caused by fecal/ oral routes. (This is when pathogens normally found in feces are transferred to eat foods resulting in cross-contamination and illness)
An obvious way that this may happen is when food handlers visit the toilet, do not wash their hands properly then handle food.
Coloured Coded Equipment
Color-coded chopping boards are a good way to keep different types of food separate.
Worktops and chopping boards will come into contact with the food being prepared so need special attention. Make sure that chopping boards are in good condition, cracks and splits could trap bacteria and this could be transferred to food.
As well as color-coded chopping boards some kitchens also provide color-coded knives, cloths, cleaning equipments, storage trays, bowls, and even staff uniforms to help prevent cross-contamination.
Clean and Sanitise
Clean and sanitize worktops and chopping before working on them and do this again after use, paying particular attention when they have been used for raw foods.
Chopping boards can be disinfected after use by putting them through a dishwasher with a high rinse temperature of 82C. (high temperatures will kill bacteria.)
Small equipment, such as knives, bowls, spoons, tongs, etc. could also be the cause of cross-contamination; it is important to wash them thoroughly, (once again a dishwasher does it well). This is especially important when used for a variety of food and for raw foods.
Take Responsibility For Food Safety
As a food handler it is your responsibility along with those working with you to assist in the control of bacteria. Keep food areas clean and hygienic at all times, clean as you go, and do not waste to build up, clean up any spills straight away. You need to be aware of protecting food from bacteria and preventing bacterial growth by keeping food clean, cool/hot, and covered where possible.
Take great care with kitchen cloths, they are a growing area for bacteria. Different clothes for different areas will help to reduce cross-contamination and it is certainly good practice o use different cloths for raw food and high-risk food areas. The use of a disposable kitchen towel is the most hygienic way to dry utensils and food preparation areas.
If a tea towel is used, treat with great care: remember that they can easily spread bacteria so don’t use it as an ‘all-purpose cloth’, don’t keep on the shoulder(the cloth touches the neck and hair, picking up bacteria).
Thorough cooking is one of the best methods available to control bacteria. Cooking to 75°C and holding that temperature at least for 2 minutes will kill most pathogens (but not spores and toxins).
Keep food being held for service above 63°C or cool it rapidly and keep below 5°C. Never put hot or warm food into the refrigerator or freezer; this will raise the temperature and put food into the danger zone.
Checking and Controlling Temperatures
Cooking food to a core temperature of 75°C for 2 minutes will kill most bacteria and these temperatures are important especially where large amounts are being cooked or the consumer is in the high-risk categories. However, some popular dishes on hotel and restaurant menus are cooked to a lower temperature than this according to individual dish and customer requirements.
Electronic temperature probes are very useful to measure the temperature in the center of both hot and cold food. They are also very useful for recording the temperature of deliveries and checking of food temperatures in refrigerators. Make sure the probe is clean and disinfected before use, (disposable disinfectant wipes are useful for this). Place the probe into the center of the food making sure it is not touching bone or the cooking container.
Check regularly that probes are working correctly(calibration). This can be done electronically but a simple and low-cost check is to place the probe in icy water, the reading should be 0C. Next, place the probe in boiling water and the temperature reading should be 100C. In both cases one degree higher or lower is acce[table. If probes read outside of these temperatures they need to be repaired or replaced. When calibration of probes has been completed, record these temperatures and keep as part of the food safety management system.