In metallurgy, usually the first step in smelting ore to extract metal. The ore is heated in the presence of an abundant flow of air to drive off moisture and, if the metal-bearing mineral is a sulfide, convert it to an oxide. Sulfur fumes from ore roasting have been a major source of environmental pollution in the past.
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Roasting is a cooking method that uses dry heat, whether an open flame, oven, or other heat source. Roasting usually causes caramelization of the surface of the food, which is considered a flavour enhancement. Meats and most root and bulb vegetables can be roasted. Any piece of meat, especially red meat, that has been cooked in this fashion is called a roast. Also, meats and vegetables prepared in this way are described as "roast", e.g., roast chicken or roast squash. Some foods such as coffee and chocolate are always roasted.
For roasting the food may be placed on a rack, in a roasting pan or, to ensure even application of heat, may be rotated on a spit or rotisserie. During oven roasting hot air circulates around the meat, cooking all sides evenly. There are several theories for roasting meats correctly: low temperature cooking, high temperature cooking and a combination of both. Each method can be suitable under the appropriate circumstances.
The objective in any case is to retain as much moisture as possible in the finished product, while providing the texture and color people prefer. During roasting, meats and vegetables are usually basted on the surface with butter, lard or oil to reduce the loss of moisture by evaporation. Recently, plastic oven bags have become popular for roasts. These cut cooking times and reduce the loss of moisture during roasting. They are particularly popular for turkeys.
Until the late 19th century, roasting by dry heat in an oven was called baking. Roasting originally meant turning meat or a bird on a spit in front of a fire. It is one of the oldest forms of cooking known.
Traditionally recognized roasting methods consist only of baking and cooking over or near an open fire. Grilling is normally not technically a roast, since grilled meat is usually seasoned with wet ingredients or marinated. Smoking differs from roasting because of the lower temperature and controlled smoke application.
Most meat roasts are large cuts of meat, and need to cook for a long time. Many roasts are tied with string prior to roasting, often using a packer's knot. Tying holds them together during roasting, keeping any stuffing inside, and keeps the roast in a round profile, which promotes even cooking.
Prior to roasting in an oven, meat is generally "browned" by brief exposure to high temperature. This imparts a traditional flavor and color to the roast. Red meats such as beef, lamb, and venison, and certain game birds are often roasted to be "pink" or "rare" meaning that the center of the roast is still red. For reasons of hygiene this practice is not recommended with pork and poultry. Although there is a growing fashion in some restaurants to serve "rose pork", temperature monitoring of the center of the roast is the only sure way to avoid foodborne disease.