What is Cross-Contamination?

By Brian Doerschuk – Gleaners Nutrition Education Team

What is Cross-Contamination?

Cross-Contamination is when pathogens (harmful bacteria or viruses) are transferred from one surface to another. This happens frequently in a kitchen setting and most of the time it is completely unintentional. It can happen when a knife is used on raw meat and that same knife is used to cut vegetables without washing it first. It can happen when you forget to wash your hands after a task and then touch food that is ready to eat. It can even happen just by touching your cell phone in the middle of preparing food! Cross-contamination is often attributed as the cause of many foodborne illness outbreaks. The good news is, it’s preventable and can be stopped with some careful planning and thinking while cooking in the kitchen.

Types of Hazards That Can Lead to Cross-Contamination

To understand and prevent cross-contamination, we first need to understand the three different types of hazards and how they can happen.

1. Physical Hazard – This could be from naturally occurring objects like cherry pits and bones left in a product or man-made objects like metal shavings from a knife sharpener that fell into food.

2. Biological Hazard – There are four different categories of biological contamination. They can be caused by bacteria, viruses, fungi, or parasites. An example of biological contamination caused by bacteria would be salmonella found in the juices of raw chicken dripping onto ready to eat food. An example of a virus would be Hepatitis A passed on by an infected food handler through unwashed hands. Fungi could be moldy bread or produce served to a person. Parasites may be found in wild game and sometimes in unwashed produce.

3. Chemical Hazard – This occurs when chemicals such as household cleaners find their way into food.

All three types of hazards are dangerous and can be a type of cross-contamination, but biological hazards lead to the most foodborne illnesses.

Types of Cross-Contamination

Similar to the number of hazards above, there are three main ways that cross-contamination can occur

1. Food to Food – One food that is contaminated impacts another food when they touch or are combined

2. Equipment to Food – Pathogens, chemicals, or physical hazards are present on a piece of equipment like a knife or a cutting board and are spread to food through contact

3. People to Food – Humans can pass their germs to the food through methods like touch or saliva droplets

All three can happen in your kitchen if you aren’t careful!

Common Sources of Cross-Contamination in the Kitchen

The easiest way to stop cross-contamination is to start by washing your hands prior to beginning a task. It shouldn’t stop there though! Any time you change tasks, such as cutting meat to slicing vegetables, pausing to take out the trash, or even stopping prep to respond to a text, be sure to stop and wash your hands again. “Why do I need to wash my hands after just touching my phone for a second?” you may ask. The average cell phone has more than 20 times the number of bacteria as a toilet seat (State food safety)! What may seem like a low-risk task could actually be the cause of you making someone in your household sick!

The next thing you can do is be sure to keep food contact surfaces such as knives and cutting boards clean and separated from dirty ones. If a recipe requires you to prepare raw meat and chop vegetables for a ready-to-eat dish like a salad, be sure to use separate knives and cutting boards or thoroughly clean and wash both the knife and cutting board with warm and soapy water after preparing the meat and before prepping the veggies.

Another common kitchen practice that is risky and can lead to illness is rinsing raw chicken or poultry. Many people believe that rinsing meat removes harmful pathogens. The truth is that you risk splashing or dripping pathogens around your kitchen and possibly on to clean counter tops, utensils, or dishes making it a very risky practice. Any bacteria that is present on the poultry will be destroyed in the cooking process (as long as the meat reaches an internal cooking temperature of 165°F).

Contrary to meat, fruit and vegetable produce should always be washed before prepping. Produce can carry harmful pathogens from the fields in which it was grown (biological contamination), pesticide residue (chemical contamination), and even dirt and rocks (physical contamination). Washing produce helps to remove these possible contaminants and prevents them from being spread around kitchen surfaces like knives, cutting boards, and counter tops.

Cross-contamination in the kitchen can happen easily and has the potential to make you and your family sick. However, it can be prevented with some careful planning and thought before beginning meal preparation. Be sure to wash produce thoroughly, but not raw meat. Always use clean utensils and food-contact surfaces (like knives and cutting boards) and be sure to wash them thoroughly when changing tasks like after cutting raw meat. Lastly, always remember to wash your hands thoroughly before prepping food, and throughout the preparation process when you stop to do things like answer your phone.

Happy Cooking!


Healthline: https://www.healthline.com/nutrition/what-is-cross-contamination#at-risk-groups
State Food Safety: https://www.statefoodsafety.com/Resources/Resources/the-dirty-cell-phone-25-127-bacteria-per-square-inch#:~:text=According%20to%20Seattle%20Times%20journalist,in%20contact%20with%20every%20day