Cross contamination is a process that involves transfer of bacteria and other microorganisms unintentionally. It could be from one item, substance or object to another, with harmful effect.
Think of it this way, you are driving on a highway and it is raining heavily, your car skid from the lane you are using to the next and hits the next car.
Obviously, this was not your intention but there is definitely some damage there. Now, there are several ways in which you could prevent that but we don’t want to get on the highway now…
In food safety, cross contamination is a key point of discussion because, you can do so much to ensure safety of your goodies but still end up with a harmful product.
According to world health organization (WHO), each year, an estimated 600 million people worldwide experience a food borne illness (https://www.who.int/NEWS-ROOM/FACT-SHEETS/DETAIL/FOOD-SAFETY). That is no small figure for something that you can easily prevent.
Unfortunately, many people assume they can only get food borne illnesses by eating in a local restaurant. That is not true and we shall see why.
The fact is, in a complete food chain, starting from the farm, harvesting, processing and manufacturing, transportation, storage, distribution, and serving at home, contamination can occur if proper precautions are not taken. However, we shall focus on what you as the consumer have control over.
Let’s dig into the know how’s of this exciting topic!
Types of cross contamination
Cross contamination can be cut into three, based on the source of the contaminant, i.e.; food to food, equipment to food, and people to food.
Food To Food Contamination
Raw, improperly washed and undercooked food can have huge numbers of bacteria and other harmful microorganisms all which are harmful if and when consumed.
If you add contaminated food to non-contaminated food, that will lead to food-to-food contamination.
There are several foods that pose a higher risk of contamination. E.g. improperly washed leafy vegetables, leftover food, unpasteurized milk, soft cheese, raw eggs, sea foods, poultry meats and other raw meat products.
If you are making a vegetable salad, and you add contaminated lettuce, it will definitely contaminate all your other delicious ingredients.
In the case of leftover food, cook to the right core temperature to destroy harmful bacteria and keep it in the fridge within 1-2hrs of cooking. Ensure it is consumed within 3-4days and your refrigerator is functioning at a recommended temperature of 4oc to prevent any bacteria overgrowth.
In the event you wish to mix your left over food with freshly cooked food, what will remain should not be stored as leftover. It will be a festivity for those tiny microorganisms and you don’t want to be part of that. Trust me you would rather patiently wait for the Christmas festivities!
Equipment To Food Contamination
What I would like you to appreciate on this is, bacteria can survive for a long time on surfaces like utensils, cutting boards, dining tables and storage containers. My microbiology lecturer once told me “Never underestimate the power of microbes”. Wise man I must say.
The multiplication rate of microorganisms is unimaginably very high. If you do not clean the surfaces you use properly, they can be a dangerous source of food contamination. Also if the surfaces are contaminated after cleaning, they can transfer a lot of bacteria or harmful microorganisms to your food.
Take a practical example, you cut raw meat with a knife, then use the same knife without cleaning to cut some clean vegetables that are going to be consumed raw. Boom! A nice playground of harmful bacteria doing pushups in readiness to diminish your health! Be careful, we want you healthy and jumpy and ……you know your best self!
A study done by PubMed’s Andrea Nesbitt et al. J Food Prot. 2009 Dec (https://pubmed.ncbi.nlm.nih.gov/20003742/) showed that older people were less likely to use soap, water and clean water to clean their cutting board after cutting raw meat, while younger people were not aware of cross contamination risks. See! Awareness is needed by all people on this.
Finally, poor food preservation methods can lead to contamination. I will refer to a refrigerator since it is what most people are aware of. It must be performing at the recommended low temperatures (4oc) as earlier mentioned. When it is under performing, what you have stored is prone to spoilage.
People To Food Contamination
We can easily contaminate food by transferring bacteria from our hands or clothes.
An example, somebody coughs into their hands, goes on to touch raw food, or cutlery and continue to prepare food for the family or guests without washing hands first! Even without food safety and bacteria knowledge, you know that is gross!
Another common practice, you are preparing food while handling your cellphone (which I believe you are not right now huh?) which is loaded with bacteria or wiping your hands with a dirty kitchen towel!
Please just wash your hands for at least 20seconds with soap and water before touching that food!
All these are unsafe food handling practices that will result in cross contamination and consequently food borne illnesses. To learn more on food safety in your kitchen click on this link to view my previous post (https://joyce-ke.com/4-simple-steps-of-hacking-food-safety-at-home/)
How To Prevent Cross Contamination
- Store raw meats in a sealed container or plastic bag and at the bottom of the shelf to prevent the juices from spreading to other stored foods.
- Use separate bags for raw eggs, meats and other groceries.
- Use refrigerated leftover food within 2-3days and cook to proper temperatures to be safe.
- Wash your hands immediately after coughing, touching a dirty surface, visiting the washrooms, using your phone, touching raw meat and anything that you think could be a contaminant. Guess what? You are right!
- Clean your cutlery, cutting boards, tables and other relevant surfaces with soap and water.
- Use separate cutting boards for the raw meats and vegetables.
- Cook food to right temperature to destroy harmful microorganisms.
- Use clean kitchen towels and dishcloths.
- When buying, avoid products that are closer to the expiry dates unless you intend to consume right away.
Stay Safe, Stay healthy, Stay informed on this site. As you have seen, it is the little things that matter in food safety!