Cross-contamination is the transfer of harmful bacteria from one food to another - this may be directly, or via chopping board, utensils, hands, etc. Cross contamination occurs when handling raw meat, especially poultry meat, because it contains more liquid than other meats. It is important to keep meats and their juices away from already cooked or ready-to-eat foods such as salads.
Uncooked poultry meat is frequently contaminated with Campylobacter but rarely with Salmonella. These bacteria are naturally present in the gut of birds, indeed all animals, and can transfer to the meat during processing.
Campylobacter is a major cause of foodborne gastroenteritis in New Zealand and raw meats, especially poultry, is one of the sources for its transmission. If you become infected with Campylobacter you are likely to become ill within 2-5 days with symptoms of muscle pain, headache and fever followed by diarrhoea and abdominal pain. The illness lasts about 5 days.
There is no way of telling that meat is contaminated with Campylobacter or Salmonella. Therefore, it is advisable to treat all meat as potentially contaminated.
To ensure you don't cross contaminate when handling raw meat:
- When shopping - separate raw meat from other foods in your shopping trolley. Place these foods in plastic bags to prevent their juices from dripping onto other foods. The poultry industry now provides whole chickens in leak-proof packs and these should be selected wherever possible
- In the refrigerator - place raw meat in containers to prevent their juices dripping onto other foods. Juices will contain harmful bacteria if they are present on the meat
- Defrosting - completely defrost meat before cooking so it will cook evenly. Ensure juices do not drip onto other foods
- In the kitchen - harmful bacteria can spread throughout the kitchen and get onto chopping boards, utensils, and bench tops. To prevent this:
- Wash hands with soap and hot water before and after handling raw meat
- Wash chopping boards, dishes, utensils and benches with hot, soapy water after preparing each food item. Preferably, use one chopping board for fresh produce and a separate one for raw meat
- It is not necessary to rinse raw meat before cooking. Studies have shown that rinsing can spread bacteria around the kitchen
- Cook raw meat thoroughly until juices run clear. This is especially important for poultry meat
- When marinating, boil used marinade before brushing onto cooked meat
- When serving, never put cooked food back on the same plate or chopping board that previously held raw meat.
Some additional cleaning tips to prevent cross contamination:
- Microwave ovens provide an effective means of sterilising wooden chopping boards (3-4 min, 800W) and cloths (wrap in paper towel and microwave until steaming, 30 sec–1 min). Rinse under tap to remove surface dirt before microwaving
- Cleaning chopping boards and cloths in a dishwasher is also an effective method of eliminating harmful bacteria
- Boards and benches can be wiped with a dilute solution of bleach (1 teaspoon bleach in 2 litres water) following cleaning to ensure harmful bacteria are destroyed.
This fact sheet was prepared on behalf of New Zealand Food Safety Authority by Environmental Science and Research.