Vol. VI · Proteins and Heat Plate 7 of 11myoglobin, meat colour, pink, metmyoglobin, premature browning, smoke ring, cured meat, donenessMS

The Colour of Meat.

Pink means myoglobin that heat has not yet changed. It usually tracks temperature — and sometimes lies.

The red of meat is myoglobin, a protein that stores oxygen in muscle. With oxygen it is bright cherry red (oxymyoglobin), without it purple (deoxymyoglobin, the colour of vacuum-packed beef), and oxidised it is brown (metmyoglobin, the colour of old meat). Heat denatures it into a grey-brown pigment, mostly between about 60 and 75 °C, which is why the inside of a steak goes from red to pink to grey as it cooks.

Usually colour tracks temperature well enough to guide a cook. But it can mislead in both directions. Minced meat that has been exposed to air or frozen can turn brown at temperatures too low for safety — "premature browning". Meat smoked, cured with nitrite, or simply at a high pH can stay pink when fully cooked: the pink "smoke ring" of barbecue, the pink of ham. That is why safety is judged with a thermometer, not by eye (XII.6).

Below: the share of myoglobin turned grey-brown against temperature (a teaching curve over 60–75 °C), and the shifts that make colour lie.

What you will learn
Workshop
Teaching model: denatured myoglobin rises over about 60–75 °C (midpoint 66 °C). Premature browning shifts the curve about 6 °C lower; nitrite, smoke or high pH hold pink about 10 °C higher.

Pink is a clue, not a measurement

For fresh meat, colour and temperature agree well enough: pink fades through the sixties. But a burger whose meat browns early can look fully grey at 60 °C, below the 71 °C that minced meat needs (XVIII.8); and cured or smoked meat at 71 °C is still only 16% browned in this model — pink, and perfectly safe. Poultry can also stay pink near the bone, especially in young birds, when fully cooked.

So use colour for what it is good at — judging how you like a steak — and a thermometer for safety. Vacuum-packed beef that looks purple will bloom red within minutes of meeting air; meat that has turned brown in the package is oxidised, not necessarily spoiled, but its colour says it is not fresh. The pink ring under the bark of smoked brisket comes from gases in the smoke reacting with myoglobin, and is a sign of smoking, not undercooking.

At the stove

Next time you grill burgers, cut one open as it reaches 60 °C on a probe and look at the colour; then cook the rest to 71 °C. You may find a 60 °C burger that already looks done: that is premature browning, and why burgers are judged by thermometer.

The pink of ham and bacon comes from nitrite, which binds to myoglobin to form a heat-stable pink pigment; curing salts have been used for centuries, long before the chemistry was known.

Terms

Myoglobin
The oxygen-storing protein that colours meat red.
Metmyoglobin
Oxidised, brown myoglobin.
Premature browning
Meat turning brown inside at temperatures too low for safety.
Smoke ring
A pink layer under the surface of smoked meat, from smoke gases reacting with myoglobin.
Colour follows myoglobin, which usually tracks temperature — but only a thermometer judges safety.

Sources

  1. USDA Food Safety and Inspection Service, "Safe Minimum Internal Temperature Chart" (foodsafety.gov), 2024.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.
  3. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.