Cooking encyclopedia Food safety

The temperature danger zone

The temperature range in which bacteria multiply fastest, and how long food may spend there.

4–60 °C (39–140 °F)

What it is

USDA FSIS gives the danger zone as 4 °C to 60 °C (40 °F to 140 °F) and the safe cumulative limit in it as two hours — one hour if the surroundings are above 32 °C (90 °F). The clock is cumulative across the whole life of the food, not reset by refrigeration.

Why it works

Bacterial growth is slow when cold and stops when hot; in between it is exponential, doubling in as little as twenty minutes at the warm end. Cooking kills bacteria but does not always destroy toxins they have already produced, which is why time in the zone matters even for food you intend to cook thoroughly.

When to use it

Thawing, marinating, cooling, transporting, buffets, packed lunches, slow-cooked dishes started from cold.

What goes wrong

Cooling a large pot on the counter overnight; marinating at room temperature; leaving a buffet out through an afternoon; adding the times up wrong because the food went back in the fridge in between.

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