What is CROSS CONTAMINATION?

Cross contamination occurs when bacteria and viruses are transferred from a contaminated surface to one that is not contaminated. Cross contamination is a key factor in food borne illness (food poisoning).The bacteria and viruses can come from people, work surfaces or equipment, and other foods. For example, it can happen when bacteria from the surface of raw meat, poultry and raw vegetables with visible dirt (such as unwashed potatoes), are transferred onto ready to eat food, such as green salads, rice or pasta salads, cooked meats or poultry or even fruit. The bacteria on the raw food are killed when the food is cooked, but the ready to eat food gets eaten without further cooking - bacteria and all.

Cross contamination has four common sources: food, people, equipment and work surfaces.

FOOD

Raw perishable foods can contain harmful bacteria. For example, raw meats contain a large number of naturally occurring bacteria such as Salmonella, Campylobacter and Listeria, which are all causes of food borne illness.
If you are not careful, harmful bacteria can easily be transferred from raw to cooked or ready to eat foods, examples of this are:-

• Due to incorrect storage methods, raw meat may drip blood and juices onto cooked foods such as ham, and quiche, or other ready to eat foods like salads, dressings and sauces.
  
• When raw and cooked foods are combined to make salad rolls, sandwiches and mixed salads, harmful bacteria may be transferred from salad vegetables to other foods (like meats, cheese or egg). If these products are then not kept refrigerated the bacteria can multiply and may cause food borne illness.
  

PEOPLE

Harmful bacteria live in and on our bodies, especially on and around our faces and hands, and on our clothing. As they are usually present in small numbers they do not make us sick. If these bacteria are transferred from our bodies or clothes onto food, and allowed to multiply, the food can become unsafe to eat.

EQUIPMENT

Bacteria are able to live and multiply in any cracks and crevices in equipment including the surface cuts of chopping boards. After equipment has been used, bits of food containing bacteria remain. If the equipment is not properly cleaned, when it is used next the bacteria will be transferred to another food.

WORKING SURFACES

Surfaces such as bench tops may have bacteria on them from contact with people, raw foods, dirty equipment or other things such as cartons that have been stored on the floor. If the bench tops are not properly cleaned, any food placed on them will be contaminated by the bacteria.

PREVENTING CROSS-CONTAMINATION

It is important to prevent cross contamination and be conscious of it while preparing food. Some tips to prevent cross contamination are listed below.

• Cover foods as much as possible.
  
• Store raw meats separate from ready-to-eat foods.
  
• In the refrigerator, store raw foods on the bottom shelves and ready-to-eat foods on the top shelves.
  
• Wash hands after handling raw meats, eggs or vegetables.
  
• Designate separate cutting boards for raw meats or clean and sanitize cutting boards between use for different foods.
  
• Clean and sanitize knives between uses on different foods and place only sanitized knives back in their racks.
  
• Sanitize any utensil, equipment, or food contact surface after it has been in contact with raw foods, especially meat or eggs.
  
• Never move boxes or containers that may have been stored on the floor onto counter tops.

References

http://www.ccc.govt.nz/Health/xcontam.asp
http://www.foodsafety.asn.au/publications/factsheets/crosscontamination.cfm
http://www.publichealthgreybruce.on.ca/FoodSafety/Preventing_Cross_Contamination.htm

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