Thickening agents give body, consistency, and palatability when used. They also improve the nutritive value of the sauce. Flavored liquids are thickened and converted into soups, sauces, gravies, and curries, etc. In other words, binding agents are used to transforming the stocks into sauces.
There are various types of thickening agents, which are used in modern-day cookery. They are as follows:
- Starches
- Flour
- Roux
- Beurre Manie
- Fruit and Vegetable Puree
- Egg yolk
- Cream
- Butter
- Blood
Starches
Starches derived from roots and vegetables are among the oldest and the most versatile thickener for sauces. They are efficient and inexpensive and that they can be used without imparting a flavor of their own.
Starches should be combined with liquid and heated to almost boiling temperature to be effective. Some starches are purer than others. Cornstarch, arrowroot starch, and potato starch are almost pure starches and produce shiny sauces, whereas flour contains protein, which gives a mat appearance to the sauces.
Cornstarch
Of the purified starches, cornstarch is the most familiar. They should be used at the last minute for the thickening of the sauces and the cooking liquid that is being served. When it is cooked for a long time then it loses its thickening power. Cornstarch is first mixed in water and then used to thicken the sauces and soups.
Arrowroot
Arrowroot is the best of the purified starches because it remains stable even after prolonged cooking. It is used the same way as cornstarch.
Potato starch
Although potato starch is one of the first starches to be used in French cooking, it has never been popular as a sauce thickener. It is used the same way as the cornstarch and like cornstarch, it tends to break down after prolonged exposure to heat.
Flour
In western cooking, flour has long been the most popular thickener for the sauces. It can be used in several ways. Although flour has largely been replaced in recent years by other thickeners. It is still the appropriate choice for many country style and regional dishes. The liquid in which flour is to be added must be degreased before the flour is incorporated. Flour binds with lamb and holds it in suspension throughout the liquid, making it difficult to skim. The result is a greasy, indigestible sauce with a muddy texture and flavor.
Roux
The most common method of thickening liquids with flour is to prepare a roux, by cooking the flour with an equal weight of butter. This enhances the flavor of the flour and eliminates the lumps. Because flour contains proteins and other compounds that impart flavor, sauces thickened with roux are usually skimmed for thirty minutes once they have been brought to simmer to eliminate the impurities. Although the stock is skimmed before the roux is added, further the sauce is skimmed to eliminate the butter, impurities in the flour.
There are three types of roux:
- White roux
- Blonde roux
- Brown roux
White roux
It is prepared by cooking flour and clarified butter for approx. 5 minutes over slow heat and stirring constantly with a wooden spoon. It is used for Béchamel sauce and thick soups.
Watch How to make white Roux Video Below :-
Blond roux
It is made from fresh butter and flour. The preparation of butter and flour is the same as for white roux. It is made more rapidly and should be made at the last before using it. Its color should be pale gold. It is used for volute sauce and some soups.
Brown roux
cooking the flour in bouillon fat in the oven, gently and for a long time, removing from time to time to stir, makes it. This roux should be light brown. It is used for brown sauce and demiglace.
How to combine roux and liquid
- When you have a hot roux, combining it with a liquid is a two-step process. In step 1, you add part of your liquid, cold to the hot roux, blending it in with a whisk. In step 2 you blend in the rest of the liquid hot.
- When you have cold roux, you can combine it with hot liquid, overheat, by blending it in with a whisk a little at a time.
Do not try to combine hot roux with hot liquid and cold roux with cold liquid.
Beurre Manie
Like roux, beurre manie contains an equal part by weight of butter and flour. It differs from roux because it is not cooked and is usually added at the end of the sauce’s cooking rather than at the beginning. It is most often used to thicken stews at the end of the cooking when the braising liquid is too thin.
The beurre manie should be added little by little in boiling stock whisking continuously so that lumps do not form. Unlike roux, the beurre manie should not be cooked once the sauce is thickened otherwise the sauce will a floury taste. One of the peculiarities of flour is that develops a strong floury taste after two minutes of cooking that begins to disappear as the cooking progresses.
Fruit and vegetable puree
Some times fruit and vegetable puree is used in thickening sauces and soups. Puree soups are the best example of the same.
Yolk
Because they thicken sauces in several ways, egg yolks are versatile liason. They provide a base for emulsified sauces, such as mayonnaise and hollandaise, and are used in conjunction with cream to finish the cooking liquid of poached meats and fish. Not only form an emulsion of fat and liquid but also combines with air so that they be used for sabayon sauce.
Sauces containing yolk should not be boiled unless they contain flour, which stabilizes them. When combining the egg yolk with liquids, be sure to combine some of the liquid separately before returning the mixture to the saucepan. If the egg yolks are added directly into the hot liquid then they are liable to coagulate as soon as they get in contact with the heat.
Cream
In recent years thickened cream has replaced roux as the thickener, becoming base for white sauces.
Precaution should be taken in reducing cream. Quick whisk should be given to the cream otherwise they become granular and may break. Always use a large saucepan, three times the volume of the cream otherwise flames from the sides can discolor the cream.
Whenever cream is used, as a thickener in a wine-based sauce, are sure to reduce the wine otherwise they giving an unpleasant flavor. The cream used in conjunction with egg yolk, butter, and flour gives a better result.
Butter
When butter is whisked into a hot liquid, it forms an emulsion, similar to the action of egg yolk. The milk solids and proteins contained in the butter acts as an emulsifier and give butter sauce their sheen and consistency. Because the milk solids in the butter are what maintain the emulsion, sauces and cooking liquids cannot be thickened with clarified butter. In fact, cold butter is proffered to hot butter in the thickening of the sauces.
Blood
Blood has long been used in cooking to finish sauces for a braised or roasted game, poultry, or rabbit. Blood not only deepens the sauce’s flavor but also acts as a thickener. The blood must be mixed with a little amount of vinegar to avoid coagulation.
