Update: Check out our all-new 2012 guide to Turkey Brining Basics.
If my mom's roasting skills are representative of the nation's, then I'll assume we've all experienced dry turkey. I'm not talking the kind that frays around the edges as soon as a carving knife comes close to it or that instantly turns to sawdust when it hits your tongue—I'm talking the kind that is just good enough that you can still smile and say nice things during dinner, but just bad enough that you wonder why the pilgrims couldn't have eaten prime rib during that first fall.
The problem, as we all know, is with overcooking. So first, a quick look at what happens to turkey (and other meats) as it cooks.
- Under 120°F (48.9°C): The meat is still considered raw. Muscle cells are bundled up and aligned in long, straight cable-like fibrils wrapped in a sheath of elastic connective tissues, which is what gives meat it's "grain."
- At 120°F: The protein myosin, begins to coagulate, forcing some liquid out of the muscle cells, which then collects within the protein sheath.
- At 140°F (60°C): The remaining proteins within the muscle cells coagulate, forcing all of the liquid out of the cells, and into the protein sheath. The coagulated proteins turn the meat firm and opaque.
- At 150°F (65.6 °C): The proteins in the sheath itself (mainly collagen) rapidly coagulate and contract. Like squeezing a tube of toothpaste, all the water what was forced out of the cells and has collected within the sheath, is now squeezed out of the meat completely. Congratulations, your turkey is overcooked.
Thanks to all those who pointed out that I should include temperature conversions in the future
Although the government will have you believe that 165°F is the minimum temperature to cook your turkey to, clearly you need your turkey to be within the 140 to 150°F range to ensure juiciness.
Below this range, and the moisture is still locked within the muscle cells. This is why raw meat tastes slippery instead of juicy—your teeth aren't sharp enough to liberate the moisture from inside the cells. Above this range, and the liquid has already gone and found a new home. But even with an accurate thermometer, you run into a problem. It may seem obvious to say it, but roasting cooks meats from the outside in. So at normal roasting temperatures—say 300°F—by the time the center of the bird is at 145°F, the exterior layers of your bird will be much higher, closer to 180 or 190°F. the result is slices that are perfectly moist and tender in the center, but overcooked and dry around the edges.
Enter brining, the process in which a lean cut of meat (like turkey, chicken breast, or pork) is soaked in a salt water solution to help it retain moisture during cooking. Sure, sure—this is nothing new. The Scandinavians and Chinese have been extolling the virtues of brining for millennia, and Cook's Illustrated has for at least a decade. But the thing that is odd to me is that people can't seem to agree on how it works—even the experts.
Let's start with what it actually accomplishes.
Spoiler Alert: One of these breasts is not like that other. In a few moments, I'm going to throw all three into a 300°F oven, roast them until they are 145°F in the very center, then quickly sear them in a hot skillet until their skin is a beautifully crisp, burnished golden brown. Only one of them will emerge fully tender and moist. The other two will end up dry and stringy around the edges.
For this experiment, I started with three nearly identical fresh, non-kosher (kosher breasts come pre-salted), non-enhanced (turkeys that come injected with a saline solution, I.E. Butterball's and Jenny-O's) turkey breasts (I admit, two were right breasts, and one was left).
One of them I left totally untreated before roasting. The second, I soaked overnight in a 6% solution of salt water (about 1/2 a cup of kosher salt, or 1/4 cup of table salt per quart of water). The third breast was a control that was soaked in pure water, just to ensure that it's actually the salt in the solution that is affecting the quality of the meat.
In order to gauge moisture loss, I weighed each breast at all stages of the process—straight from the butcher, just before roasting, just after emerging from the oven, and just before slicing, making sure to subtract the weight of the fat deposited in the roasting pan from each breast to compensate for any differences in fat loss.
Here's what happened:
The blue line represents the untreated turkey breast, which ends up losing around 24% of its weight in moisture-loss during cooking. The brined turkey, on the other hand, lost only about 15% of its weight, while the water-soaked turkey lost around 20%. Clearly, brining works, and it's specifically the salt in the soak that helps the turkey retain moisture while its cooking.
And the best part? Since a brine works from the outside in, it affects precisely those areas of the turkey breast that are most prone to drying out—the exterior layers.
Let me demonstrate:
This is a macro shot of two slices taken off of the roasted, unbrined turkey breast. Now, don't get me wrong—if someone served this to me at a Thanksgiving meal, I'd be more than happy to eat it. In fact, the very center of the slice is absolutely perfect. But as you can clearly see, it's the last half-centimeter around the edge that starts to dry out.
Now, take a look at this:
These are two slices taken from the brined turkey breast. Even the outermost layers, which rose to temperatures well in excess of 150°F, are still moist and juicy, forming perfectly smooth, even slices.*
*I apologize for the slight blurriness of the focus on the front of the slices—this is a photographer error, and not a poorly executed airbrushing job.
How it Works
So the salt solution is somehow helping the turkey retain more moisture as it cooks. But how?
One common explanation is that it is pure osmosis, the movement of water across a semi-permeable membrane. Cell walls are designed to allow water and small molecules to move in and out of them freely, while preventing larger molecules from entering or leaving—this is how it gets the raw materials it needs to live without losing any of its "guts."
This movement of water and small soluble compounds is controlled by osmotic pressure. Essentially, whenever there is an imbalance of the concentration of solutes across two sides of a permeable membrane, water will pass through the membrane until the concentration is equalized.
So how does this explain brining? Well, unfortunately, it doesn't, and we can prove this without even knowing the concentration of solutes inside the cells to begin with. Let's look at three possible scenarios.
Scenario 1: There is a higher concentration of solutes within the cells.
In this case, in order to equalize the concentration, water should flow from the brine into the cells. Seems to make sense—except that as we've already seen, soaking in pure water is less effective than soaking in salt water (see graph above). If osmotic pressure was the only thing bringing water into the meat, then a soak in pure water (which creates a higher differential in solute concentration between the interior and exterior of the cells) should force more water into the cells than a soak in salt water.
Scenario 2: There is an equal concentration of solutes within the cells.
In this case, osmosis does not even enter into it. There may be an exchange of solutes as sodium ions change places with small molecules inside the cells through diffusion, but this should have no effect on the amount of water taken up by the meat
Scenario 3: There is a lower concentration of solutes within the cells.
In this case, the laws of osmosis state that water would migrate from within the cells to the outside. Your turkey meat should actually dry-out even more if your salt solution is too concentrated.
In a bid to demonstrate that osmosis is not the key factor in brining, I conducted an experiment based on scenario three: I brined a turkey breast in a fully saturated salt water solution (for example, a solution with as much salt as I could possibly dissolve in it)—around 35% salt by weight—and compared it to a turkey breast in a 6% brine solution.
While the fully-saturated-brined turkey on the left had outer layers that were inedibly salty (remember—diffusion), both turkeys lost about the same amount of weight during cooking, indicating that rather than effecting osmosis, the salt must be doing something entirely different.*
Turns out that the real answer has to do with the shape of proteins. In their natural state, the muscle cells are tightly bound within their protein sheaths—this doesn't leave much room for excess water to collect in the meat.
But as anyone who has ever made sausages or cured meats knows, salt has a powerful effect on muscles. A 6% solution of salt will effectively denature (read: unravel) the proteins that make up the sheath around the muscle bundles. In this loosened, denatured state, you can now fit more water into those muscles than in their natural state. Even better, the denatured proteins in the sheaths contract far less as they cook, therefore squeezing out much less moisture.
Now, given that most of you food nerds have probably been brining for years, is knowing all this really going to make your turkey taste better this Thanksgiving?
Nope. But at least it gives you something to talk to your relatives about besides gluten formation in laminate pastry pie crusts.
UPDATE: Check out our all-new 2012 guide to Turkey Brining Basics.
*Disclaimer: I know I'm going to eventually get beat up in the comments section for not mentioning this, so I will say now that yes, osmosis does actually enter into the equation in a minor way: as salt diffuses into the actual muscle cells, they break down some of the cells internal structure, releasing solutes into it. Provided your brine concentration is low enough, this can create a difference in osmotic pressure that will cause some water to actually migrate into the cells themselves instead of just into the protein sheaths surrounding them.
That said, once the turkey is cooked and the liquid is squeezed out from within the cells, it is the moisture trapped in the protein sheaths that gives the sensation of juiciness—not the liquid that was inside the cells before it was even cooked, as is clearly demonstrated by the last experiment using a fully-saturated brine solution.