Grilling Science: Why Medium Rare Steak Just Tastes Better

 

As steak fanatics, we know better than to cook well-done.

When we go into the medium-well/well-done range, our steaks begin to lose any pleasant flavor or texture, and this type of cooking has even been linked to high blood pressure. And so, we always know to aim medium-rare (or thereabouts). It brings the perfect balance of flavor and texture, giving us something to chew on, while still maintaining the integrity of our raw product.

A next logical question is, of course: how does it work? Why is medium-rare the perfect steak?

While the rabbithole of thermodynamics is basically infinite, today we are gonna quickly get in and out to explain why exactly a medium-rare is so perfect.

Get on your lab coats, and bust out the grill - We're about to learn.

If we zoom way, way in on any piece of meat, we can get a look at what is happening during cooking on a cellular level. On that microscopic level, meat is made of protein strands. Of all of these proteins, we are going to be looking at just two today: myosin and actin. Put simply, myosin is the word for the thicker, stronger muscle filaments, and actin is the word for the finer, thinner filaments.

 

The changes to these components within the animal change as soon as slaughter occurs. When an animal enters into rigor-mortis, enzymes within the muscles are quickly activated. These enzymes permanently contract the myosin and actin, both of which become unable to re-enter their relaxation phase. When cooking, we are looking to break down this little ecosystem, thus allowing the muscles to ‘relax’ and the meat to become tenderized.

 

So how do we get there? Well, it’s quite simple. We want to change the myosin strands, but leave the actin filaments alone. Luckily, myosin fibers become altered at a much lower temperature than their actin counterparts.

 

Myosin begins to change at just 104°F. When the myosin denatures, it fundamentally alters the structure of the meat. As the larger fibers begin to change, moisture is still able to be kept in the muscle structure. The texture goes from raw and tough to relaxed and tender, giving our steaks that juicy, melt-in-your mouth quality that is found at medium rare.

 

If we continue to escalate our temperature up towards the well-done range, at about 150°F, we start to see negative effects. These finer, smaller fibers begin to dry out and toughen in the higher temperature ranges. The actin proteins also allow huge amounts of moisture loss when they shrink and tighten to this degree, resulting in a dry, tough steak.

 

As you can see, there’s a sort of ‘perfect range’ of temperature, according to the science of thermodynamics. We want to activate the larger muscle fibers (myosin), while basically leaving the smaller strands (actin) in their natural state.

 

It’s a simplified version on the cellular structure of the steak, but with the knowledge of what is really going on when we cook, we can cook better steaks and thus, better meals.

 

In short: The longer you cook a steak, the dryer and tougher it gets. Since the flavor of a steak comes from the juices, it makes sense to retain as much of those as possible.

In case you're unsure of what temperature correlates with which level of doneness, here's a handy little guide to meat temps!

Meat Temperature Guide: