Foodborne Illness and Food Safety Hazards
Foodborne illness and food safety hazards
This domain tests how well you can recognize biological, chemical, and physical hazards, name the pathogens most often linked to foodborne illness in Ontario, and explain the conditions that let bacteria multiply and produce toxins. Questions often use a scenario and ask for the most likely cause or the safest corrective action.
Core rules
- Biological hazards are the biggest cause of foodborne illness: bacteria (Salmonella, Campylobacter, E. coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, Clostridium botulinum, Bacillus cereus), viruses (norovirus, hepatitis A), parasites, and moulds.
- Chemical hazards include sanitizer residue, unapproved pesticides, medicines, and allergen proteins. Physical hazards include glass, metal, bone, plastic, and jewellery.
- Bacteria need food, moisture, time, temperature, oxygen or its absence, and acidity. High-risk foods are protein-rich, moist, and near-neutral pH: meat, poultry, seafood, eggs, dairy, cooked rice, cut melons, sprouts, and sauces.
- Spore formers survive cooking; Bacillus cereus in cooked rice and Clostridium perfringens in stews are classic examples. Toxin producers such as Staphylococcus aureus can leave heat-stable toxins that cooking does not destroy.
- Viruses such as norovirus and hepatitis A are spread mainly by infected handlers and contaminated water or produce; they do not multiply in food, but a very small dose can cause illness.
Worked example
A caterer cooks rice at 4 p.m., leaves it covered on the counter until 9 p.m., then reheats it for service. Guests develop vomiting 2–6 hours later. The likely hazard is Bacillus cereus: the rice stayed in the danger zone, spores germinated, and toxin formed. Reheating may kill cells but not the toxin. The safe action is to cool rice rapidly, refrigerate it, and discard it if it has been above 4°C for more than two hours.
Traps
- Smell, taste, and appearance do not prove food is safe.
- Freezing does not kill bacteria; it only stops growth.
- Food poisoning is not always from the last meal eaten; incubation periods vary.
- Do not confuse intoxication (toxin already present) with infection (pathogen grows in the body).