Bacterial Contamination
Food Preparation & Nutrition: AQA GCSE, topic 4.1.4
Cross-Contamination
Cross-contamination is the process by which bacteria pass from one food to other foods. Cross-contamination can happen through:
Food that's already contaminated
- Contaminated high risk foods contaminating other foods.
- Raw foods leaking onto cooked foods.
People
- Cooking with unwashed hands.
- Sneezing without using a tissue.
- Coughing without covering your mouth.
Cooking utensils and surfaces
- Not cleaning equipment properly before or after use.
- Preparing raw and cooked foods on the same surface.
Pests
- May plant eggs or excrete onto cooking surfaces.
- May also contaminate food by landing on it or eating it.
Controlling Bacteria
Untreated eggs and milk are both highly susceptible to contamination. To make these foods safe, we can:
Pasteurise milk
- The process involves heating milk to 72°C for approximately 15 seconds.
- This should destroy pathogenic bacteria before the milk is chilled.
- All milk must be pasteurised before being sold in UK supermarkets.
Vaccinate hens
- Many years ago, the UK introduced a programme for vaccinating hens against salmonella.
- Eggs and boxes of eggs that have come from vaccinated hens are stamped with the British Lion Quality mark.
Test yourself on Bacterial Contamination
What do we call the process by which bacteria pass from one food to other foods?
How can people cause cross-contamination of food?
Which of the following practices could cause cross-contamination of foods?
What are eggs that have come from vaccinated hens stamped with in the UK?