Food Safety Hazards and Contamination
This domain tests whether you can classify a food safety hazard, trace how contamination reaches food, and explain why some foods are inherently riskier than others. Exam items usually give you a short scenario and ask you to name the hazard type, the contamination route, or the control measure that would have prevented it - so learn the categories cold and practise mapping examples onto them.
The four hazard categories
- Microbiological - bacteria, viruses, yeasts, moulds and parasites. The main cause of food-borne illness. Some bacteria spoil food without making you ill; some pathogens make you ill without obvious spoilage.
- Chemical - cleaning chemicals, sanitiser residues, pest baits, oil breakdown products, heavy metals, mycotoxins and naturally occurring toxins.
- Physical - glass, metal, hard plastic, bones, stones, packaging, plasters, jewellery, pests and pest droppings.
- Allergenic - the 14 regulated allergens. Often listed as a separate category because the harm is immune-mediated and does not depend on numbers of organisms.
Contamination routes
Direct contamination means the hazard goes straight from source into food (a sneeze onto open sandwiches). Indirect contamination uses a vehicle - hands, cloths, chopping boards, knives, tap handles, packaging. Cross-contamination is the transfer of pathogens from raw to ready-to-eat food, or from a contaminated source to a clean surface.
What makes a food high risk
High-risk foods are ready to eat, moist, protein-rich, near-neutral pH and high water activity. Typical examples: cooked meat and poultry, pâté, dairy products, cooked rice, shellfish, prepared salads, gravies and stock. Low-risk foods are dry, acidic, heavily sugared or salted, or still raw and intended for cooking.
Worked example
Frozen chicken is defrosting on the top shelf of a fridge and drips onto an uncovered bowl of coleslaw below. Question: what hazard type and what route? Reasoning: the drip contains Campylobacter or Salmonella - microbiological. It travels by an indirect route, with the drip as the vehicle, and it is cross-contamination because raw poultry fluid has reached ready-to-eat food. The control is to store raw meat below ready-to-eat food in a lidded container on the bottom shelf.
Traps that cost marks
- Calling allergens "chemical hazards" when a question asks specifically about hazard categories.
- Assuming freezing kills bacteria - it does not; it only pauses growth.
- Confusing spoilage with pathogenicity. Smell and appearance are not safety tests.
- Forgetting that people, pests and waste are contamination sources in their own right.
- Treating "cross-contamination" as a hazard type rather than a route.