Cross-contamination occurs when harmful microorganisms, allergens, chemicals, or other contaminants are unintentionally transferred from one food, surface, utensil, piece of equipment, or person to another.
It is one of the major food safety risks because contamination can occur without any obvious change in the appearance, smell, or taste of food.
For example, raw chicken may contain harmful bacteria. If a cutting board is used to prepare raw chicken and is then used to cut vegetables without proper cleaning and sanitizing, microorganisms from the chicken may be transferred to the vegetables.
Common Sources of Cross-Contamination
Cross-contamination can happen in many different ways.
Raw and Ready-to-Eat Foods
Raw meat, poultry, seafood, and eggs should be kept separate from foods that are ready to eat. Raw foods can contain microorganisms that may be destroyed during proper cooking but can cause illness if transferred to food that will not be cooked.
Cutting Boards and Utensils
Different foods should be prepared using appropriate equipment and procedures. Cutting boards, knives, containers, and other utensils should be cleaned and sanitized appropriately between different tasks.
Hands
Hands can transfer microorganisms from one food to another. A person who handles raw chicken and immediately prepares a salad without washing their hands may contaminate the salad.
Food Storage
Food should be stored in a way that prevents liquids from raw foods from dripping onto ready-to-eat foods. Raw foods should generally be positioned appropriately within refrigerators and storage areas to reduce this risk.
Cleaning vs. Sanitizing
Cleaning and sanitizing are related but different processes.
Cleaning removes visible dirt, food particles, grease, and other materials from a surface.
Sanitizing reduces microorganisms on a properly cleaned surface to a safer level.
Both steps are important when required by food safety procedures.
Preventing Cross-Contamination
Some effective prevention practices include:
- Keep raw and ready-to-eat foods separate.
- Wash hands between different food-handling activities.
- Clean and sanitize food-contact surfaces appropriately.
- Use suitable equipment for different food preparation activities.
- Store raw foods safely.
- Keep food containers properly covered.
- Avoid placing cooked food on surfaces that previously held raw food.
- Follow established cleaning and sanitation procedures.
Cross-Contamination and Allergens
Cross-contact can also be important when dealing with food allergens. Even a small amount of an allergen can cause a reaction in someone who is sensitive to it.
For this reason, food handlers should follow appropriate procedures when preparing food for people with allergies. Equipment, surfaces, ingredients, and storage practices may need to be carefully managed to prevent unintended exposure.
A Practical Example
Imagine a worker preparing a meal. They first cut raw chicken, place the chicken aside, and then use the same knife and cutting board to chop lettuce for a salad.
Even though the lettuce looks clean, it may have been exposed to microorganisms from the raw chicken.
The correct approach would be to follow the appropriate cleaning and sanitizing procedure or use clean equipment before preparing the salad.
Preventing cross-contamination requires attention to the movement of food, people, equipment, and contaminants throughout the entire preparation process.