Food Safety Hazards and Foodborne Illness
A hazard is any agent in food that can cause illness or injury. Candidates must distinguish biological (bacteria such as Salmonella, Listeria, Campylobacter, E. coli; viruses such as norovirus; parasites; moulds), chemical (cleaning chemicals, pesticides, allergens, toxins), physical (glass, metal, stones, packaging) and allergenic hazards. Understand the conditions bacteria need to multiply - food, moisture (water activity), warmth (the 5–60 °C danger zone), time, acidity and oxygen - and the difference between intoxication (toxin already formed in food, e.g. Staphylococcus aureus) and infection (live cells ingested, e.g. Salmonella).
Know the high-risk foods (moist, protein-rich: cooked meat, dairy, seafood, cooked rice, eggs) versus low-risk (dry, acidic, high-sugar). Recognise common sources and controls: raw poultry and Campylobacter, raw eggs and Salmonella, unpasteurised dairy and Listeria, cooked rice left at room temperature and Bacillus cereus.
Traps: questions often ask for the most likely cause given a scenario, or test whether a hazard is biological or chemical (mould toxin = biological; cleaning residue = chemical). Allergens are sometimes classed separately - read the options. Don't confuse food spoilage (food looks/smells bad but may be safe) with foodborne illness (pathogens may be present with no change in appearance).
Worked rule of thumb: If a scenario describes vomiting within 1–6 hours after eating, suspect a pre-formed toxin (S. aureus or B. cereus); if symptoms appear 12–72 hours later, suspect infection (Salmonella, E. coli). Use onset time to reason to the hazard.