Stock (food)
Stock, sometimes called bone broth, is a savory cooking liquid that forms the basis of many dishes, particularly soups, stews and sauces. Making stock involves simmering animal bones, meat, seafood, or vegetables in water or wine, often for an extended period. Mirepoix or other aromatics may be added for more flavor. Preparation. Traditionally, stock is made by simmering various ingredients in water. A newer approach is to use a pressure cooker. The ingredients may include some or all of the following: Bones: Beef and chicken bones are most commonly used; fish is also common. The flavor of the  stock comes from the bone marrow, cartilage and other connective tissue. Connective tissue contains collagen, which is converted into gelatin that thickens the liquid. Stock made from bones needs to be simmered for long periods; pressure cooking methods shorten the time necessary to extract the flavor from the bones. Meat: Cooked meat still attached to bones is also used as an ingredient, especially with chicken stock. Meat cuts with a large amount of connective tissue, such as shoulder cuts, are also used. Mirepoix: Mirepoix is a combination of onions, carrots, celery, and sometimes other vegetables added to flavor the stock . Sometimes, the less desirable parts of the vegetables that may not otherwise be eaten (such as carrot skins and celery cores and leaves) are used, as the solids are removed from stock. Herbs and spices: The herbs and spices used depend on availability and local traditions. In classical cuisine, the use of a "bouquet garni" (or "bag of herbs") consisting of parsley, bay leaves, a sprig of thyme, and possibly other herbs, is common. This is often placed in a sachet to make it easier to remove once the stock is cooked. Types. Basic stocks are usually named for the  primary meat type. A distinction is usually made between "fond blanc", or white stock, made by using raw bones and mirepoix, and "fond brun", or brown stock, which gets its color by roasting the bones and mirepoix before boiling; the bones may also be coated in tomato paste before roasting. Chicken is most commonly used for "fond blanc", while beef or veal are most commonly used in "fond brun". Other regional varieties include: Health claims. By early 2010s, "bone broth" had become a popular health food trend, due to the resurgence in popularity of dietary fat over sugar, and interest  in "functional foods" to which "culinary medicinals" such as turmeric and ginger could be added. Bone broth bars, bone broth home delivery services, bone broth carts, and bone broth freezer packs grew in popularity in the United States. The fad was heightened by the 2014 book "Nourishing Broth", in which authors Sally Fallon Morell and Kaayla T. Daniel claim that the broth's nutrient density has a variety of health effects. There is no scientific evidence to support many of the claims made for bone broth.