The Cooking Process: Part 2

In addition to temperature and time, the makeup of the food itself is a determining factor in the changes cooking brings about. Foods are made up of varying combinations of the following substances:

1. Proteins

2. Carbohydrates

3. Fats and oils

4. Vitamins and minerals

5. Water

Nutritionally these substances, taken together, provide energy (measured in calories); they build and maintain bones, body tissues, and blood cells; and they keep everything in working order. In a well balanced diet, protein should provide 10 to 15 percent of the calories, carbohydrates 55 to 58 percent, and fats and oils not more than 30 percent. Vitamins, minerals, and water contribute no calories but are essential to growth and health. One of the goals of good cooking is to conserve the nutrient values of foods.

These different components of foods react in certain distinctive ways to the heat of cooking. If you understand these reactions, you can control the changes and obtain the results you want.

Proteins

Foods high in protein are the flesh foods (meats, poultry, fish), milk products, eggs, nuts, and certain vegetables. Nutritionally, proteins are the major building and maintenance materials of the body. On the menu, foods high in protein are the entrees, the backbone of the meal.

In cooking, heat causes proteins to coagulate, to become firm, join, cohere. You can see this happen before your eyes if you fry an egg over low heat: the transparent liquid becomes white and opaque as the heat reaches it. If you cook it too long or at too high a temperature, it toughens and thus becomes too firm. The same thing happens in flesh cookery: as the temperature of the product increases, the protein firms. Overcooking will make the flesh tough.

If you heat milk too rapidly or too long, its protein will coagulate into curds and separate from the liquid whey, and we say it has curdled. This will spoil your soup, sauce, or custard. Cheese, which is made from milk curd, reacts to high or prolonged heat by quickly becoming tough, stringy, and unmanageable.

Connective tissue in meats is formed of certain kinds of protein that are naturally tough. The type known as collagen can be broken down and changed into gelatin by cooking at low temperatures with moisture. Acids can also soften meat fibers to some extent, as in marinating on the other hand; acid can reinforce the coagulation process. Adding vinegar to the water in which eggs are poached makes a firmer, more compact and shapely product.

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