Which of the following is an example of cross-contamination?

• A. Using the same surface to cut raw chicken and onions
• B. Preparing onion rings with wheat-based breading in the dedicated gluten-free fryer
• C. Using the same spatula to prepare peanut-containing and peanut-free cookies
• D. Storing allergen-containing foods on the same shelf as allergen-free foods

Answer: (A)

Cross-contamination happens when harmful microorganisms or allergens are transferred from one food to another through contact with contaminated surfaces, utensils, or equipment. Using the same surface to cut raw chicken and onions puts bacteria from the raw meat onto the cutting board, and those bacteria can be carried to the onions. If those onions are eaten raw or undercooked, illness can result. The other scenarios involve preventive measures or different types of contamination: a dedicated gluten-free fryer is used to prevent gluten from transferring to gluten-free foods, so it’s about preventing cross-contact rather than demonstrating it; using the same spatula for peanut-containing and peanut-free cookies risks transferring peanut proteins via the utensil, which is a form of allergen cross-contact; and storing allergen-containing foods on the same shelf as allergen-free foods can also cause cross-contact, but the direct transfer on a prep surface is the clearest, most immediate example of cross-contamination.