Thickening Agents
Nearly all civilizations in the world are considered to have been founded upon the production of cereals, as they provide a nutritious food containing the important elements needed for an adequate diet (1971). It has been reported that the agricultural era began about 10,500 years ago when people in fertile regions of the Middle East began to cultivate weeds and grasses, producing mostly wheat and barley, and about 1000 years later, a similar process happened in China where rice and millet were cultivated from wild grasses ( 2006). Moreover, it was not until the great civilizations rose that a certain cultural phenomenon took hold, that of purifying or whitening wheat flour, being proven as early as 350 BC, in the writings of about commercial baking with sifted flour. By 50 AD, sifted flour was being produced on a large scale in most Mediterranean countries, making whole wheat bread as a food for peasants, slaves and athletes ( 2006).
Thickening agents, thickeners or food additives are substances which, when added to a mixture, increase its viscosity without modifying its other properties, such as taste, and provide body, increase stability and improve suspending action of the mixture ( 2006). Some food thickeners include wheat flour, roux, beurre manie and cream.
The first known domesticated cereal is wheat and originated in southwest Asia in the area known as the Fertile Crescent and its earliest archeological evidence for cultivation comes from the Levant and Turkey around 10,000 years ago (2006). Wheat flour is a powdery substance derived by grinding or mashing the whole-wheat grain and is used in baking but typically added to other “white” flours to give nutrition, texture, fiber, and body to the finished product. Usually, it is not the main ingredients of baked goods, as it adds a certain heaviness, which prevents them from rising, and adds to the cost per volume of the baked item, as it requires more flour to obtain the same volume, due to the fewer and smaller air pockets trapped in the raised goods. It has a shorter shelf life compared to white flour for a higher oil content leads to rancidification (the decomposition of fats and other lipids by hydrolysis or oxidation), making it more expensive than other flours (2006). Among the food products produced from wheat flour are breads, pastas, crackers, many cakes, and is used to make a roux as a base for gravy and sauces (‘Flour’ 2006).
Another thickening agent is called roux, which is a mixture of butter or fat and wheat flour, cooked until bubbly (2006). Butter, vegetable-based oils or lard are the common fats used in making roux. It is said to be the basis of three of the five mother sauces of classical French cooking, namely, Sauce béchamel, Sauce veloute, (white sauces) and Sauce Espagnole (a brown sauce), and is used as a base for gravies, other sauces, soufflés, soups and stews (2006). The thickening of the sauce is explained by the mechanism of cooking the flour in the butter. The starch granules present in the wheat flour begins to break, thus, when the liquid is added, the granules absorb the liquid, thickening the sauce (2006). In any roux-bound sauce, care must be taken to avoid lumps, such as by adding either a cold liquid to a hot roux or a hot liquid to a cold roux, and constantly whisking the mixture while the liquid is added (2006). Preparation of a light roux is rather simple, while preparation of dark roux presents danger of burning, especially over high heat (2006).
As an alternative to using roux, beurre manie can be used as a thickening agent. Beurre manie is a thickening agent having equal parts of unsalted butter and wheat flour, kneaded to a dense paste, and gently whisked into the sauce (2000). Furthermore, by kneading the flour and butter together, the flour particles are coated in butter, and when the beurre manie is added to a hot or warm liquid, the butter melts, releasing the flour particles without creating lumps, so a liquid thickened with beurre manie should be heated for at least another 20 minutes to prevent it from tasting of flour (2006). It is also called a “manipulated butter” and similar to the roux, except that the flour is added in equal proportions to cold butter (1998). It is added to soups, stews and sauces as a thickening agent.
The last thickening agent to be discussed is cream. Cream is a handy and rich addition to soups for its proteins have been greatly diluted by fat globules and are less likely to form a skin when heated or boiled. It is also immune to curdling in the presence of acidic or salty foods ( 2006). Its production is an overtime process, where in the raw milk the lighter fat is waited to rise to the top, while in industrial processes, it is accelerated by using centrifuges called “separators”. It is sold in several grades depending on total butterfat content, and even can be dried to a powder-form, for shipment to distant makers. Cream produced by cows grazing on natural pasture often contains some natural carotenoid pigments derived from the plants they eat, giving it a slight yellow tone or a yellowish-white color, while cream from cows fed indoors, on grains or grain-based pellets is white (2006).
Cream is used as an ingredient in many foods, adding texture and flavor, in food products including ice cream, many sauces, soups, in some custard bases, and in cakes (2006). Cream has several kinds, which can be added to food products for better results. One type of cream is the heavy or whipping cream, which has a milk fat content of about 36 to 40% (1997). It is mixed with air and roughly doubles the cream’s volume as air bubbles are captured in a network of fat droplets (2006). Another type of cream is the Finnish light or single cream, which has a milk fat content of about 10%. Light cream cannot be whipped and it is best used in drinks like coffee or creamy cocktails. In cooking, it is best to add light cream to foods or sauces towards the end of cooking to prevent curdling (1997). Other types of cream include the artificial cream or the imitation of cream made from non-dairy fats, the butter cream, or the cake icing, the crème anglaise or light pouring custard used as a dessert cream or sauce, and the pastry cream or crème patissiere, a stirred custard thickened with starch (2006).
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