Meat is placed on a wire rack in the oven rather than directly on the bottom of a pan. This lets hot air circulate beneath the meat so every surface browns at the same time. Meat placed directly in the pan sits in its own juices underneath and steams instead of browning. The rack also lets rendered fat drip away, so the meat does not cook in a pool of fat. This improves both browning and the sauce.
An oven cooks with hot air circulating around the food, and that air can do its job only where it reaches the meat’s surface. The underside of meat placed directly in a pan does not meet the air, and liquid released from the meat collects in the pan and surrounds it. The result is meat that is browned on top but pale and wet underneath. A wire rack raises the meat a few centimeters and creates an air gap below it, allowing all surfaces to start browning together.
The second benefit is separating the liquid. Water and rendered fat drip through the rack into the pan instead of leaving the meat sitting in them. With meat placed directly in the pan, fat collects underneath and effectively fries the bottom, changing both its texture and flavor. Do not discard the drippings; together with the browned bits on the bottom of the pan, they form the base for a sauce. Adding a little water or stock to the pan helps keep the drippings from burning and makes it much easier to collect the sauce.
The difference is most noticeable with poultry. For chicken skin to become crisp, it needs to stay dry; steam from liquid collected in the pan wets the skin and prevents it from crisping. On a rack, the skin can dry and brown all over. The same principle applies to spatchcocked chicken, wings, and bone-in thighs. Pat the skin thoroughly dry and salt it before cooking; these two steps complement the benefit of the rack. Vegetables behave the same way: vegetables arranged in a single layer with space between them brown, while vegetables piled in a pan steam.
Not every dish needs a rack. Meat in soups, stews, and steamed dishes is already cooked in liquid, so a rack serves no purpose there. A rack may also be omitted when meat is roasted with vegetables because the drippings are meant to flavor the vegetables. For large cuts cooked slowly at a low temperature, a rack is still preferred, but add about a finger’s depth of water to the pan to keep drippings from burning and smoking. If you do not have a rack, arrange thick-cut onions and carrots under the meat to create the same gap; they can then be added to the sauce.
The wire rack also needs care. Brush it while it is still hot after use; residue hardens as it cools and cannot be removed afterward. Before cooking, apply a thin coating of oil to the rack to reduce sticking. When placing the roasting pan and rack together, make sure the rack fits securely in the pan, since a wobbly rack can tip the meat. Do not use abrasive scouring powder when washing it. Whatever setup you choose, determine doneness with a thermometer: use 74°C / 165°F for poultry, and 63°C / 145°F plus a 3-minute rest for a whole cut of red meat such as beef or lamb. Check the points where the rack rests on the pan each time you wash it; rust on the rack can stain the meat.