Before a lot of emphasis was placed on leaner meats, even tender cuts of meat had a contained a lot of fat, in the form of “fat cap.” The fat cap is the thick layer of fat covering meat. On a live animal, the fat would be between the skin and the meat. In today’s market, the fat cap is trimmed before sale.
During roasting, the fat cap melts and bastes the meat, keeping it moist. With the leaner cuts of today, we need to work harder to keep the end product moist. I said it’s harder, but not impossible. There are several ways to ensure a moist product. Some are healthier than others, but all will improve ensure a juicy and flavorful end result.
Larding is actually a very old form of introducing extra fat to a cut of meat. Strips of solid fat, such as lard or bacon fat, are pulled through slits in the meat with the help of a large needle. During roasting, the strips of fat melt: self-basting meat. Since most of the extra fat melts away during the cooking process, larded meat does not taste “fatty,” just more flavorful. Larding is an effective method of increasing juiciness, but as you can imagine, it is labor intensive.
Brining is an effective method of keeping meats moist during roasting. In its simplest form, a brine is just a salt and water solution, but you can introduce all sorts of additional flavors in the form of herbs, spices and aromatics. Brining works through osmosis to introduce salt and other flavors into the meat.
Once in the cells of the meat, the salt causes partial denaturing and coagulation of the proteins in the meat. This coagulation keeps the moisture in the cells, preventing drying out. Most of us think about turkeys when we think of brining, but any lean cut of meat can be brined to add moisture and flavor. I think you have a brining page—maybe link to the recipe for a basic brine?
A marinade is usually a flavorful steeping liquid that contains an acid (vinegar, wine, lemon juice, etc). The acid helps to break down some of the outside tissues to break down and hold more liquid. This can make a more flavorful end product. Marinades tend to work just on the surface of foods, so they are not very effective in flavoring large cuts although they can work wonders on smaller cuts of meats. Consider a marinade for a smaller cut that you want to pan roast.
When you baste, you are bathing the outside of the meat with butter, pan drippings or a flavorful sauce during the cooking process. While this can help to keep the roast moist, it also lowers the cooking temperature in the oven when you open it. If you choose to baste, do it quickly and give the oven enough time to come back to temperature between basting.