The word marinade comes from the Latin/Italian "marinara" which means "of the sea." The original marinades (from several centuries ago) were briny liquids like seawater meant to preserve, tenderize and flavor foods. Not that much has changed. Marinades still serve two major functions:
- Immersion in flavor, and
- Tenderizing
However, many opportunities for exploration and experimentation still abound. Meanwhile, some basic questions:
What With? How Long?
The three main marinade "families" are acids, enzymes, and dairy.
Acid bases include vinegar, wine, citrus juice and tomatoes. Acidic marinades denature proteins, which may actually toughen the chicken. When exposed to an acidic marinade, the bonds between protein bundles in the meat break and the proteins unwind. They run into each other and form a loose mesh. Initially, water is trapped within this protein "net" and tissue remains moist and juicy. After a short time, however, the protein bonds tighten, water is squeezed out, and the tissue toughens. Because of this, when using a highly acidic marinade for chicken, you may want to add a little olive oil and/or minimize marinating time. Two hours is usually more than sufficient for these marinades.
Enzymatic marinades, which work by breaking down the muscle fiber and connective tissue (collagen), are another approach--but may make chicken mushy. Kiwi, papaya, raw pineapple, honeydew melon and figs all contain protein enzymes (proteases), but again, may work too well if the marinating/breakdown of proteins is allowed to continue for too long. In this case the meat may turn to mush without passing though an intermediate stage of tenderness. Again, two hours is usually long enough to marinate chicken in this marinade family.
Dairy products such as buttermilk or yogurt are only mildly acidic and are probably the only marinades that truly tenderize. They don't toughen meat the way that the strongly acidic marinades do. It seems that the calcium in dairy products activates enzymes in meat that break down proteins; this process is more similar to the way that aging tenderizes meat than to cooking it, which is what the highly acidic marinades begin to do.
Keep in mind that the "toughening" which may occur with highly acidic marinades and long marinating times is not necessarily drastic; it may, in fact, hardly be noticeable. But if you've found that those overnight-marinated chicken breasts sometimes seem tough, even a little "cooked," you now know why and can simply lessen/adjust the marination time accordingly.
Marinating for 12 hours or more does cut cooking time by about 1/3, so keep an eye on the grill.
How Much?
You do want your chicken to be completely immersed in/covered by the marinade. Generally, 1/2 cup of liquid marinade for every 1 pound of meat will do the trick. If the meat is not completely covered, you will need to turn it over occasionally, making sure all sides get equal treatment during the chicken's stay in the refrigerator.
In What?
It is best to marinate in either a glass dish or a resealable plastic bag; the dish enables even covering, the bag allows the liquid to almost completely cover the chicken--if not, it can be turned over again and again with no spill, no mess. Do not use an aluminum dish or aluminum foil, as there might be a chemical reaction which can result in off colors and flavors.
What Not?
Never use leftover marinade for basting or as a sauce, unless you first boil it for 3-5 minutes to kill any bacteria. When properly boiled and bacteria-free, marinades do make a lovely, tasty sauce.
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