Temperature Control and the Temperature Danger Zone
The Temperature Danger Zone (TDZ)
The temperature danger zone is 5°C to 63°C (41°F–145°F). Bacteria multiply fastest between 20°C and 50°C. Food should be kept below 5°C (cold holding) or above 63°C (hot holding). The 2-hour/4-hour rule is a practical guide: food in the TDZ for less than 2 hours can be refrigerated or used; 2–4 hours can be used immediately but not returned to refrigeration; over 4 hours must be discarded.
Safe Temperatures
- Refrigerator: ≤5°C (ideally 1–4°C).
- Freezer: ≤-18°C.
- Cooking: poultry and stuffed foods to 75°C; minced meat to 71°C; whole cuts to 63°C (with rest time).
- Cooling: from 63°C to 21°C within 2 hours, then to 5°C within a further 4 hours (total 6 hours).
- Reheating: to 75°C within 2 hours, once only.
Traps in Questions
- Using the wrong end of the TDZ (e.g., 0–5°C is safe, not dangerous).
- Forgetting that cooling must be rapid and in two stages.
- Assuming reheating can be done multiple times-only once.
- Confusing holding temperatures with cooking temperatures.
Worked Example / Rule of Thumb
A large pot of stew is cooked at 2 pm and left on the stove to cool. By 6 pm it is still at 30°C. This is unsafe because it has been in the TDZ for over 4 hours. Correct method: divide into shallow containers and cool rapidly (e.g., blast chiller or ice bath). Rule of thumb: Keep hot food above 63°C, cold food below 5°C, and limit time in the TDZ to 2 hours maximum.