The Analysis

Three fundamental physical facts about a piece of steak on a hot pan are:

1. The steak will not heat itself from the inside. The heat has to come from outside.
2. Heat transfers inside the steak by conduction. The speed of heat conduction is finite, and it’s a property of the steak itself.
3. The Fourier law, which states that in conduction, the heat transfer rate (heat flux) is proportional to the temperature difference and the inverse of heat resistance.

According to Fourier's law, we can increase heat flux either by reducing the heat resistance or by increasing the temperature difference. To reduce heat resistance, we can add oil, which is a good heat conductor. To increase the temperature difference, we should wait until the pan is really hot before we put the meat in it. Another benefit of a really hot pan is that the food will not stick to the pan, partly due to the Leidenfrost effect.

The violent sizzling sound you hear when you drop a piece of steak in a hot pan is the water on the surface of the steak getting vaporized. If you don’t hear anything, that means your pan is not hot enough. However, the sizzling sound should not last too long. If it does, it means there is too much water on the steak. All the evaporation of water takes a lot of energy away, which causes the pan temperature to drop. At that point, you are not searing your steak; you are boiling your steak.

A common misconception is that searing the meat locks in the juice. Last I checked, nobody is making raincoats out of seared meat. Actually, meat juice and soluble proteins continue to leak out of the meat throughout the cooking process. When they run into the hot pan surface, the water evaporates, and the protein coagulates and participates in the Maillard reactions. That’s why you don’t see any liquid. But you will see meat juice on the serving plate when the surface of the steak cools down on the plate.

Figure 2: Changing temperature profile

Our goal is not to cook the steak as fast as possible. Our goal is to get the desired temperature profile inside the steak. Assuming the meat starts at 30°C and the pan is at 200°C, a minute after the meat is put in the pan, the temperature profile inside the meat looks like the blue line in Figure 2. All the water at the surface has evaporated, and a thin layer of meat has dried out. The temperature drops as we go deeper into the meat. We then run into a boiling zone, where the water boils and the temperature stays at 100°C. After the boiling zone, the temperature continues to drop.

After a few more minutes, more of the steak is dried out, and the Maillard reactions happen there. The boiling zone moves further inside the steak. Over time, the dried-out zone on the outside gets thicker, and the boiling zone continues to move further inside. This is shown as the red curve in Figure 2.

We want to make sure all the meat is cooked to above 60°C, but we want to limit the expansion of the high-temperature/dried-out region to get something like the brown curve in Figure 2. In other words, we want to raise the tail of the red curve while making it less steep. This means we must have a smaller heat flux into the steak. Traditional recipes will ask you to move the steak into a slow oven and let it finish. If you are patient, you can set the oven temperature lower to ensure a smaller heat flux into the steak. How long should you leave it in the oven? Don’t trust any recipe, the oven thermostat, or your own experience. Stick a meat thermometer sideways into the steak and monitor the temperature.

There is a final twist: to achieve your target temperature, you must remove the steak from heat before the internal temperature hits 60°C. The reason is this: when the steak is in the oven, the hottest part is the surface. When the steak is removed from the oven, the heat on the surface can go in one of two directions: it can go inside the steak, or it can go out into the air. It turns out air is not a very good conductor of heat (that’s why the fluffy down comforter keeps you warm), so the residual heat from the surface of the steak will dissipate inwards and continue to cook the inside of the steak. You can easily confirm this by sticking a meat thermometer in your steak and seeing its internal temperature rise. In my kitchen in the summer, the temperature in the middle of the steak keeps rising for up to 15 minutes. Effectively, this is continued gentle cooking.

Unfortunately, relying on the residual heat is neither reliable nor repeatable. How much the temperature rises is different for different pieces of steak in different kitchens. It depends on the humidity of your kitchen, the ambient temperature, and whether there is a draft in your kitchen, among other things.

The steak does not absorb the meat juice when it’s resting. It’s true that if you cut open a piece of hot meat, a lot of juice flows out. But if you wait until it cools down, no juice seems to be flowing when you cut the steak. The real reason is that liquid is more viscous at low temperatures. For instance, water’s viscosity at 80°C is about 1/3 of its viscosity at 20°C. At a lower temperature, gelatin from the meat also forms a gel that further impedes the movement of the juice. That’s why sauces always become thicker between the hot stove and the table.

I suppose if you carefully control the heat, the thickness of the meat, the fat content and water content of the meat, and the timing, you can skip both the low oven step and the resting step to get a good temperature profile. That seems to be what some well-known steakhouses do, according to videos on YouTube.