To brine means to soak something in a salt solution, and it works because of a principle you learned in high school chemistry: osmosis, or the tendency of fluids to diffuse through cells in order to equalize ion concentrations. Techspeak aside, it means that when you soak a turkey (or other meat) in brine for long enough, it absorbs some of the moisture—6% to 8% of its original weight, in fact—so when you cook the turkey, you start off and end up with a moister bird.
Now for the bonus part: Some of the salt and any other flavors you add to the brine also migrate into the bird, so your turkey becomes more flavorful. Not only that, but the salt causes a change in the turkey’s protein structure that allows it to better hold on to its moisture. What could be better?
Brining isn’t just for turkey. Any lean meat—like pork, chicken, or shrimp—is ideal for brining. The smaller the item, the less time it needs in the brine.
Don’t overcook. Brining doesn’t completely protect meat against dryness, but it will give you more leeway.
Jazz up your brine with other flavors. Add herbs and spices, a little of a flavorful sweetener (like honey or maple syrup), or replace some of the water with another liquid like apple cider or coffee. Just remember that when you add sugar, foods tend to brown faster.
Keep it cold and rinse it well. Raw meat is still raw meat, whether it’s in brine or not. Always keep foods below 40°F while brining, and then rinse them well to remove excess salt from the surface before cooking.
Be careful when adding more salt. The brine provides just about all the seasoning you need, so be judicious about adding more just before cooking. Always taste first when making sauces with pan drippings, which tend to be quite salty already.