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:
Leftover cooked meat, such as that remaining on poultry carcasses, is often used along with the bones of the bird or joint. Fresh meat makes a superior stock and cuts rich in connective tissue such as shin or shoulder of beef or veal are commonly recommended, either alone or added in lower proportions to the remains of cooked poultry to provide a richer and fresher-tasting stock. Quantities recommended are in the ratio of 1 part fresh meat to 2 parts water. Pork, although a popular base for stock in Chinese cuisine is considered unsuitable for stock in European cooking due to its greasiness (although 19th century recipes for consomme and traditional aspic included slices of mild ham) and mutton was traditionally avoided due to the difficulty of avoiding the strong tallowy taint imparted from the fat.
Veal, beef, and chicken bones are most commonly used. The flavour of the stock comes from the cartilage and connective tissue in the bones. Connective tissue has collagen in it, which gets converted into gelatin that thickens the liquid. Stock made from bones needs to be simmered for longer than stock made from meat. Pressure cooking methods shorten the time necessary to extract the flavour from the bones.
Mirepoix is a combination of onions, carrots, celery, and sometimes other vegetables. Often, the less desirable parts of the vegetables (such as carrot skins and celery ends) are used that may not otherwise be eaten. The use of these parts is highly dependent upon the chef, as many do not appreciate the flavours that these portions impart.
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.
Today, ready-made stock and stock cubes consisting of dried, compressed stock ingredients are readily available. These are commonly known as bouillon cubes, as cooking base in the US, or as Oxo cubes in Britain, after a common brand of stock cube sold there.
Comparison with broth
The difference between broth and stock is one of both cultural and colloquial terminology but certain definitions prevail. Stock is the thin liquid produced by simmering raw ingredients: solids are removed, leaving a thin, highly-flavoured liquid. This yields classic stock as made from beef, veal, chicken, fish and vegetables.
Broth differs in that it is a basic soup where the solid pieces of flavouring meat or fish, along with some vegetables, remain. It is often made more substantial by adding starches such as rice, barley or pulses.
Traditionally, broth contained some form of meat or fish; however, nowadays it is acceptable to refer to a strictly vegetable soup as a broth.
Fish stock is made with fish bones and finely chopped mirepoix. Fish stock should be cooked for 20-25 minutes—cooking any longer spoils the flavour. Concentrated fish stock is called "fish fumet." In Japanese cooking, a fish and kelp stock called dashi is made by briefly (3–5 minutes) cooking skipjack tuna (bonito) flakes called katsuobushi in nearly boiling water.
Fond blanc, or white stock, is made by using raw bones and white mirepoix. Chicken bones are the most common for fond blanc.
Fond brun, or brown stock. The brown color is achieved by roasting the bones and mirepoix. This also adds a rich, full flavour. Veal bones are the most common type used in a fond brun. Tomato paste is often added (sometimes thinned tomato paste is painted onto the roasting bones). The acid in the paste helps break down the connective tissue helping accelerating the formation of gelatin, as well as giving color to the stock.
Glace viande is stock made from bones, usually from veal, that is highly concentrated by reduction.
Remouillage is a second stock made from the same set of bones.
A few basic rules are commonly prescribed for preparing stock:
The stock ingredients are simmered starting with cold water. This promotes the extraction of collagen, which may be sealed in by hot water.
Stocks are simmered gently, with bubbles just breaking the surface, and not boiled. If a stock is boiled, it will be cloudy.
Salt is usually not added to a stock, as this causes it to become too salty, since most stocks are reduced to make soups and sauces.
Meat is added to a stock before vegetables, and the "scum" that rises to the surface is skimmed off before further ingredients are added.
If the cook wants to remove the fat, after the stock is finished it is cooled and the fat, which floats, separates and solidifies into globs within the stock, which can be removed with ease.
Stocks can be frozen and kept indefinitely but are better fresh.
The refrigerator shelf life of a stock is three to four days, but the stock can be boiled at the end of this period and the life extended another three to four days. Stock can be kept for extended periods in this manner.