The Significance of Meat Resting: Insights from The Food Lab

The Food Lab will be exploring the importance of resting your meat this week. Asides from over/under-cooking/seasoning, not resting meat properly is probably the cooking blunder that we are all most guilty of.

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Why you should rest your grilled meat
Do you mean I will have to wait until I get my perfectly charred ribeyes? Unfortunately, yes.

Here’s why:

This picture shows a medium-rare steak cooked in a pan to 125degF (51.7degC). After immediately placing the steak on a cuttingboard and slicing it in half, a flood of juices poured out onto the board.

What is the result? The result? A steak that’s not as juicy and flavorful as it could be. Allowing your steak to rest prior to slicing can easily prevent this tragedy.

The center of the steak is super-saturated with liquid

As I was told, this occurs because the juices from the surface of the steak are forced towards the center as it hits the hot pan or grill. This increases the moisture concentration in the middle. The same thing occurs on the opposite side of the steak once it’s flipped. When you cut the steak open, it will be dripping with liquid. Resting the steaks allows all the liquid that has been forced from the edges into the middle to move back to the edges.

It makes some sense, doesn’t it? Imagine a bundle of straws representing muscle fibers. Each straw is filled with liquid. As the meat cooks these straws begin to change, becoming narrower and placing pressure on the liquid within. The meat is cooked from the outside out, so the straws will be pressed most firmly at the edges and slightly less firmly in the center. So far so good. If the edges are pressed more tightly than the middle, then liquid should be forced to the center.

Here’s the issue: water does not compress. It is physically impossible to add more water to a bottle that has been filled to capacity with water. The same thing applies to a steak.

There is no way of forcing more liquid into the muscles unless we stretch the fiber centers to make them wider. By measuring the circumference of the raw and cooked center of a steak, you can prove that the fibers do not get wider. The circumference would increase if liquid was being forced into the middle. It does not. The edges may shrink and give the appearance of a larger center, but it isn’t.

The exact opposite is true. The center of the medium-rare steak, which reaches 125degF at its highest temperature, is also shrinking and forcing out liquid. Where does the liquid go?

It can only come out of the ends of the straws or the surface of the meat. What is that sizzling sound you hear when a steak cooks? This is the sound of moisture escaping or evaporating*.

There are ways to reduce the shrinkage and moisture loss of muscle fibers. This topic will be discussed in a later Food Lab.

Put That Theory to Rest
Why does a steak that has not been rested expel more liquid than one that has? It turns out that temperature is the key.

This change is irreversible. We know that the thickness of the fibers in the muscles is directly proportional to the temperature at which the meat is cooked. The meat will not be able hold as much liquid in its raw form as it would if it was cooked at 180degF. Once the meat is cooled, it relaxes, the muscle fibers expand slightly. This small change in shape makes all of a difference.

This picture shows six steaks that are all the same thickness and were cooked to 125degF. I cut one steak every 2.5 minutes, and then placed it on a dish to catch any juices.

What’s happening?

After no resting: The meat surrounding the outside of the steak is well above 200degF (93.3degC). They are tightly closed at this temperature, which prevents them from retaining any moisture. The steak’s center is 125degF. The meat can still hold some of its juices, but cutting it open will cause liquid to spill.
After 5 minutes of resting, the outermost layer of meat is down to about 145degF (62.8%C), and the center steak is still at around 125degF. The muscle fibers are now a little more relaxed and have stretched out a little. This stretching creates a difference in pressure between the center and ends of the fiber, which pulls some liquid from the middle to the edges. The liquid content in the middle of the steak is reduced. If you cut it open, some liquid will still leak out, but much less than before.
After 10 minutes of resting, the edges of the meat have cooled down to about 125degF. This allows them to absorb even more liquids from the middle of the meat. The center of the meat has cooled to about 120degF by now, which causes it to slightly widen. When you cut the meat at this point, the liquid is evenly distributed and thinly spread throughout the steak. Surface tension will keep the liquid from spilling onto the plate.
The difference between the two steaks is huge. Take a look at the two steaks below:

All those succulent juices spill out of the steak on the right. The steak on the left is a good example of everything staying inside.

How do we know if the juices are really inside the steaks after they have rested? It’s possible that during the 10 minutes I allowed the steak to rest, the liquid didn’t evaporate and leave me with a dry steak.

Weighing the steaks both before and after cooking will prove that this isn’t true. The majority of weight is lost from the juices of the meat, not from rendered fat.

Just by cooking, the steak will lose around 13 percent of its original weight. If you cut it immediately, you will lose another nine percent. Allow it to rest and you will lose an additional 2 percent.

Larger Meats
This is all very well for steaks. But what about larger cuts, like a whole roasted loin of pork or a prime-rib? The same principles also apply. The main difference is that they need to rest longer. How long should I rest? There are several rules: five minutes for each inch of thickness; ten minutes for every pound; half the total cooking time.

The thermometer is by far the most reliable and easiest way to determine if meat has rested enough.

No matter how well you cook your meat, it’s best to let it cool until the center reaches 120degF. The muscle fibers will have relaxed to the point that juices should not be lost. This is shown on the graph. For a 1.5 inch thick steak, it takes around 10 minutes. Prime rib can take up to 45 minutes.

Congratulations! Your meat has become seven percent more delicious.

The Food Lab is back for another round. Have a topic suggestion? Kenji will do his best in the future to respond to your questions.

Continue here to see Pan-seared steaks with Red Wine Pan Sauce

Pan-Seared Steaks Recipe with Red Wine Pan Sauce

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