The Cooking Process: Part 3

Carbohydrates include starches, sugars, and cellulose, or fiber They are found mainly in plant foods such as cereal grains, vegetables, and fruits; in products made from cereal grains such as flours and cornstarch; in milk; and in refined sugar products such as granulated sugar and sugar syrups.

Nutritionally, starches and sugars are the body's main sources of energy. Those from grains, rice, fruits, and vegetables are the most useful to the body, while refined sugar is often said to contribute "empty calories." On the menu, starches and sugar are served in bread and rolls, desserts, rice, pasta, cereal, potatoes and some other vegetables, and many soups and sauces.

In cooking, heat affects the three types of carbohydrates in different ways. With starches, the most important change that heat brings is gelatinization. This is the process by which dry starch granules (flour, cornstarch, and so on) absorb moisture in the presence of heat, thickening and binding the food with which they are mixed. This is an important part of making soups and sauces, and it plays a role in baking. You will understand gelatinization better when we deal with these products. Acid can affect this process too: adding lemon juice, tomato, or wine can result in a thinner product unless it is added at the end after gelatinization is complete.

The most important change heat brings to sugar is caramelization. High temperatures will cause chemical changes in sugars that alter their flavor and color, turning them brown. The heat must be dry: if water is present the sugars will dissolve, and because they are then limited by the boiling point of water they cannot reach high enough temperatures to caramelize until most of the water has evaporated.

Sugar can be caramelized by itself, or the sugar contained in a food product can be caramelized, as in the browning of baked goods and the caramelization of sugar in browned onions and in hash browned potatoes. Similar browning occurs in meats seared or sautéed at high temperatures.

Cellulose, or fiber, is the substance that gives structure and texture to fruits, vegetables, and grains. The effect of heat on fiber in the presence of moisture is to soften it. This will make it more palatable, up to a point. However, a certain firmness of texture is often desirable. One of the marks of the skilled cook is the ability to produce the exact texture desired in cooked fruits, vegetables, and such starchy foods as pasta and rice.

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