Full mechanism, in text

Cook it to 74°C in the center

1 · Killing bacteria is a speed, not a switch

Heat kills bacteria at a speed: the hotter, the larger the share inactivated per unit of time, so safety depends on how hot and how long together.Bacteria do not vanish as a group the moment a certain temperature is reached. Heating unfolds the proteins inside them, and that happens at a speed: the hotter, the larger the share inactivated per unit of time.

What decides safety has always been how hot and how long together — not either number on its own.

2 · The rule picks the convenient point on the curve

The household rule picks a temperature high enough to meet the target almost instantly, and you need to reach it at least, not exactly.A household rule has to be a sentence anyone can carry out, so it picks the convenient point on that curve: hot enough that you are essentially there in an instant. The time dimension then shrinks to something you can ignore.

The correct use: you do not need to hit it exactly. You need to reach it at least.

3 · Colour is a proxy, not the quantity

Meat colour comes from myoglobin and shifts with acidity, freeze history and bird age, so only a thermometer in the thickest part reads whether it is heated enough.What makes meat look red is myoglobin, and its colour is affected by acidity, freeze history, and the age of the bird. Meat heated enough can still look pink near the bone; meat that looks all white can still be short at the centre.

A thermometer in the thickest part is a direct reading of the quantity you actually care about.

4 · The danger is on what you do not intend to cook

Rinsing raw chicken splashes bacteria onto counters, sinks and raw vegetables that will not be heated, so the danger is there, and separating matters more than cooking through.Rinsing raw chicken helps the wrong side: splash sends colonies to counters and vegetables that will not be heated. The danger is not in the piece you are going to cook.

Campylobacter does not need a large dose, and does not need to multiply first. For it, separating matters more than cooking through.

Chicken — temperature times time

Full mechanism, in text

1 · Killing bacteria is a speed, not a switch

2 · The rule picks the convenient point on the curve

3 · Colour is a proxy, not the quantity

4 · The danger is on what you do not intend to cook

Chicken — temperature times time

Full mechanism, in text

1 · Killing bacteria is a speed, not a switch

2 · The rule picks the convenient point on the curve

3 · Colour is a proxy, not the quantity

4 · The danger is on what you do not intend to cook