Marinades serve two important purposes. The first, we are all well aware of, is to add flavor to your food. The second is to tenderize.
Obviously, cuts of meat are as different as can be and that means that marinades should be too. Some meats are more tough than others, some more naturally flavorful than others. Because of all the different types and cuts of meet there are many ways to prepare a marinade. The three main categories of marinades are acids, enzymes, and dairy.
bases include vinegar, wine, citrus juice and tomatoes. Acidic marinades break down proteins. This can 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.
marinades work by breaking down the muscle fiber and connective tissue. This can make chicken mushy so use care with this method and expect a little trial and error (as with any method). Kiwi, papaya, pineapple, honeydew melon and figs all contain protein enzymes. They may work too well, leaving the meat mushy, if allowed to marinate too long. As with acid bases, two hours is generally plenty of time marinate chicken in this marinade category.
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 natural way that aging tenderizes meat than to cooking it, which is what the highly acidic marinades begin to do.
Whether you are looking to tenderize a tough cut of meat or looking to kick up the flavor of that great chicken your choices are endless. With a little knowledge of marinade basics and a willingness to try some new things you can have the best marinades in town.