Bacteria and temperature: the danger zone
Also searched as: food safety, danger zone, bacteria, keeping food warm, cooling leftovers, salmonella
In short: Bacteria multiply fastest between about 10 and 50 °C. Cold slows them down; thorough heating kills most of them.
Like weeds in spring: in mild weather they grow overnight; in frost and in heat they rest.
Simplified model
Temperature thresholds
5
- 5 °Cfridge: bacteria strongly slowed
- 10 °Cfrom here: fast growth
- 50 °Cup to here: fast growth
- 65 °Ckeep warm at least
- 70 °Cheating: at least at the core
Below 5 °C none of this happens yet. From 5 °C: fridge: bacteria strongly slowed.
What happens
In pleasant warmth, bacteria divide every few minutes to hours. The fridge slows them down a lot but does not kill them. Only enough heat makes meat and leftovers safe: food safety authorities recommend at least 70 °C at the core. Cooked food should pass through the warm range quickly, taking at most about two hours to cool.
Why it matters
Explains why is cooked through, why leftovers should not sit on the stove for hours and why keeping food warm means keeping it hot.
Rules of thumb
- Heat poultry, minced meat and leftovers to at least 70 °C at the core.
- Keep food warm at 65 °C or more, otherwise cool it quickly.
- Put leftovers in shallow containers in the fridge within two hours.
- Thaw in the fridge, not on the kitchen counter.
Levers
2
In practice
2
Poultry
Always cook chicken through: at least 70 °C at the core for two minutes.
Rice and grains
Do not leave cooked rice standing warm for long; cool it quickly.