It’s one of the biggest misconceptions about meat, but that blood-like liquid in the packaging isn’t actually blood.
It makes sense that you’d assume the liquid at the bottom of a meat package is blood – it looks like blood; comes with raw meat like you would expect blood to; and can even smell a little like iron, which is contained in blood. But this is one of those rare cases where deductive reasoning fails us, and looking like a duck, swimming like a duck and quacking like a duck does not, in fact, make it a duck.
In reality, that blood-like liquid is what scientists call ‘purge’ – a combination of water and meat proteins that drain from meat. It’s one of those proteins, water-soluble myoglobin, that gives the water its red or dark pink colour (the same protein is responsible for the reddish pink colouring of the meat itself). Myoglobin is similar to hemoglobin, the protein that gives blood its colour, but it isn’t blood.
Meat is typically 75 per cent water, which is what gives cooked meats their juiciness. For comparison’s sake, the adult human male is about 60 per cent water, and the adult human female is roughly 55 per cent. This is why your cooked steak is always smaller than what you first put on the grill – water evaporates as it’s cooked.
The proteins in meat, then, are the sponges that absorb the water. As the meat ages, and is handled or cut, the proteins progressively lose their ability to hold onto that water, and when it’s released, the myoglobin flows out with it.
The colour of the ‘purge’ is primarily determined by how old the animal was when it was harvested. Animals harvested at a younger age contain less myoglobin than older animals. Pigs, for instance, tend to be harvested at a younger age than cows, so the purge packaged with pork is predominantly pink, while the purge packaged with steak is a darker red.
Myoglobin also changes colour when it’s cooked, which is why a rare steak will ooze red juices, while a well done steak’s juices will be clearer.
While it might be reassuring to know you’re not handling cow’s blood when you open your packaged steak (or disappointing, if you’re a vampire), keep in mind that you should still take care when handling ‘purge’.
It can carry the same bacteria as a raw piece of meat, so you’ll still want to wash your hands after touching it; try to contain it to prevent cross contamination; and avoid consuming it until it’s been cooked to a proper temperature.
In the end, it’s just another lesson in not judging a book by its cover – or a liquid by its colour.