Thickening agents give body, consistency, and palatability when used. They also improve the nutritive value of the sauce. Flavoured 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.
Below are the various types of thickening agents, which are used in modern-day cookery:
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 the flavour of their own.
Starches should be combined with liquid and heated to almost boilingtemperature to be effective. Some starches are purer than others. Cornstarch, arrowroot starch, and potato starch are almost pure starches and produces shiny sauces, whereas flour contains protein, which gives a mat appearance to the sauces.
a. 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. It is also known as SLURRY.
b. 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.
c. Potato starch: (Fecule) 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.
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 flavour.
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 flavour of the flour and eliminates the lumps. Because flour contains proteins and other compounds that impart flavour, 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 1) White roux 2) Blonde roux 3) 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.
Blond Roux: Is made from fresh butter and flour. The preparation of butter and flour are the same as for white roux. It is made more rapidly and should be made at the last before using. Its colour should be pale gold. It is used for volute sauce and for some soups.
Brown Roux: Cooking 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 of light brown colour. It is used for brown sauce and demiglace.
Steps for combining roux and liquid:
1. 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.
2. 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.
3. Do not try to combine hot roux with hot liquid and cold roux with the cold roux.
(Manipulated Butter ) 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.
Sometimes fruit and vegetable puree are used in thickening sauces and soups. The puree soups are the best example of the same
Because they thicken sauces in several ways, egg yolks are a versatile liaison. 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 poachedmeats 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 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.
In recent years thickened cream has replaced roux as the thickener, becoming base for white sauces. Precaution should be taken in reducing cream. A 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 discolour 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 flavour. The cream used in conjunction with egg yolk, butter, and flour gives a better result.
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 thickening of the sauces.
Blood has long been used in cooking to finish sauces for the braised or roastedgame, poultry, or rabbit. Blood not only deepens the flavour of the sauce but also acts as a thickener. The blood must be mixed with a little amount of vinegar to avoid coagulation.
It is the mixture of egg yolk and cream mixed in the proportion of 1: 3 ratio and added to the sauce and soup in last moment just prior to service. After adding to the food, the food should not be heated. The word is derived from the French means ‘to bind”.
It is a cooked mixture of equal proportions of flour and butter with some liquid being mixed in the ratio of 1: 1: 5. They play a prominent part in Larder preparations of various products. Their main function in recipes is to act as binding. Types of panadas are Bread, flour, frangipane, potato and rice panadas. Sometimes to get a coating consistency the ratio will be 1:1:10 and for a basic pouring consistency, this will change 1:1:20.