Foodborne Illness and Food Safety Hazards
Hazards and the conditions that make them dangerous
A food safety hazard is any contaminant that can cause illness or injury. Biological hazards - bacteria, viruses, parasites, and mold - account for most foodborne illness. Chemical hazards include cleaners, pesticides, allergen cross-contact, and toxic metals picked up from galvanized containers or acidic food in contact with copper. Physical hazards are foreign objects: glass, bone, metal shavings, fingernails, bandages.
Bacteria need the FATTOM conditions: Food, Acidity (pH 4.6–7.5), Time, Temperature (the 41–135°F danger zone), Oxygen, and Moisture (water activity 0.85 or higher). Foods that support rapid growth are called TCS foods - meat, poultry, fish, shellfish, eggs, dairy, cooked rice and pasta, cut melons, leafy greens, sprouts.
Know the Big 6: Norovirus, Hepatitis A, Salmonella Typhi, nontyphoidal Salmonella, Shigella, and Shiga toxin–producing E. coli. These are the pathogens that trigger exclusion of a food worker. Viruses do not reproduce in food and are not reliably killed by cooking.
Traps
- Mixing up infections and intoxications: Staphylococcus aureus and Bacillus cereus make heat-stable toxins, so reheating spoiled food does not make it safe.
- Believing freezing kills bacteria. It only stops growth.
- Forgetting that spore-formers (Clostridium perfringens, Bacillus cereus) are the classic cooling and reheating failures.
Rule of thumb
Apply the 4-hour rule: TCS food that has spent 4 hours total in the danger zone must be thrown out; keep it under 2 hours whenever you can.