Cross-Contamination Prevention and Cleaning and Sanitizing
Cross-contamination prevention and cleaning and sanitizing
This domain tests how contamination moves between foods, surfaces, hands, and equipment, and the difference between cleaning and sanitizing. Ontario exams often ask for the correct order of steps or the correct sanitizer concentration.
Core rules
- Cross-contamination occurs when bacteria or allergens move from raw food, dirty equipment, hands, cloths, or drips to ready-to-eat food. Prevent it with separate boards, utensils, containers, and storage zones; raw food below ready-to-eat food; covered containers; and handwashing between tasks.
- Cleaning removes food, grease, and soil with detergent and water. Sanitizing reduces microorganisms on a clean surface using heat or an approved chemical. A surface cannot be sanitized effectively if it is still dirty.
- Manual dishwashing: wash in hot soapy water, rinse in clean water, sanitize in an approved solution, then air dry. Do not towel-dry food-contact equipment.
- Common sanitizer strengths: chlorine 100 ppm for food-contact surfaces, quaternary ammonium 200 ppm, iodine 25 ppm. Use test strips and follow the manufacturer directions; too strong is a chemical hazard, too weak is ineffective.
- Clean and sanitize food-contact surfaces after each task, when changing from raw to ready-to-eat food, after spills, and at least every 4 hours during continuous use. Keep wiping cloths in sanitizer and change the solution.
- Clean non-food-contact areas on a schedule; separate cleaning chemicals from food.
Worked example
A worker cuts raw chicken, wipes the board with a dry cloth, and immediately slices lettuce for a salad. The board is still contaminated with Campylobacter or Salmonella. The correct action is to discard the lettuce, wash and sanitize the board and knife, wash hands, and use a clean board or colour-coded board for the lettuce. A dry wipe only spreads contamination; sanitizer needs a clean surface and contact time.
Traps
- Sanitizer does not work on visible food soil.
- Rinse and air dry without a sanitizing step is not enough for food-contact surfaces.
- A stronger sanitizer is not better; it can leave toxic residue.
- Sponges and dirty cloths can spread bacteria; use single-use towels or laundered cloths.