Proteins by the Millions of Bushels


What is the answer to the protein problem—a problem that is becoming more critical as the world’s population increases and its food supply diminishes? One answer lies in the proper use of the soybean, a protein source that has been cultivated extensively for centuries. Millions of bushels of this plant, one of the richest yielders of protein known to mankind, are now being produced in the United States each year.

Recognizing the great food value of the soybean, how may it best be prepared to provide nourishing and palatable dishes for the family table?

The protein content of soybeans is astonishing. Such beans as navy, great northern, kidney, and lima beans contain 20 to 25 prepared with meat at 70 cents a pound, dry milk at 50 cents a pound, eggs at 50 cents a pound, and cheddar cheese at 60 cents a pound, clean soybeans can be obtained for 10 to 12 cents a pound. Generously assuming that the protein content (approximately 30 percent) of each of these foods is the same, the cost of soy protein is one-fourth to one-fifth the cost of the other protein sources.

The nutritional quality of the protein is a most important consideration. The human body needs approximately 45 grams, or one and a half ounces, of protein each day. After digestion into its constituent molecules, protein is absorbed into the bloodstream and utilized by all parts of the body. The molecules that make up protein are differentiated into twenty-two different kinds of amino acids. But while some amino acids may be produced in the body from an abundance of other amino acids, ten kinds that are termed essential cannot be made in the body. If sufficient essential amino acids are not available, normal body functions suffer. The body is not in danger, however, unless an extended condition of deficit essential amino acids prevails.

Some children in Latin America have only a bean and corn diet after weaning and suffer in both mental and physical development from lack of quality protein. Protein from milk, eggs, and meat is high quality—that is, it contains sufficient essential amino acids—and soy protein is almost its equal in quality. Children in Taiwan who were fed soy and rice flour enriched with minerals grew as well as children who drank cow’s milk.

Preparation of soybeans for human consumption requires some knowledge of the unique characteristics of this unusual bean. Most beans contain 50 to 60 percent starch, which, when cooked, becomes gelatinized and soft. While soybeans do not contain starch, they have a 20 to 30 percent carbohydrate content. Overcooking of soybeans breaks down the protein and generally results in a bitter flavor.

Soybeans may be ground up in a blender to facilitate their use in a number of foods; however, they should be cooked for 10 to 15 minutes before being ground. Without cooking, ground soybeans develop a paintlike odor due to the catalytic activity of natural enzymes acting on the oil present. A second important reason for cooking soybeans before eating is to destroy trypsin, a natural digestive enzyme inhibitor.

Soybeans may be utilized for food in a number of ways. The simplest is to soak them for four hours or even overnight, then cook them 15 minutes, drain them, add a light sprinkling of salt, and eat them like salted peanuts. These are nicknamed cheesebeans after their mild, cheesy flavor.

Soybeans that have been cooked in the soaking water and ground 5 minutes in a blender may be used in any recipe that calls for cow’s milk. A half cup of dry beans will make one quart of “soy milk.” This “milk” may be drunk after a pinch of salt and a teaspoon of sugar have been added to improve the flavor. Because it is difficult to grind soybeans fine enough, a slight chalky after-feel in the mouth is evident; straining through a cloth eliminates this, but it also eliminates much of the nutritional value. Interestingly, when soy milk is used in pancakes, browning is slower, the batter may be thicker, and more moist pancakes result. A slight bean flavor carries over but is not offensive.

A tasty, creamy soup may be prepared with thick soy milk (1 cup soaked beans for 2 or 3 cups liquid) to which is added beef or vegetable bouillon.

Soy curd may be prepared from thick soy milk (1 cup soaked beans and 1 1/2 cups water) with the addition of 2 or 3 tablespoons of vinegar. The acidified mixture is drained through a cloth until 1/2 cup of whey is obtained. The curd may then be mixed with more or less equal parts of hamburger for a meat loaf, spaghetti sauce, or hamburgers. With soy curd present, more of the natural meat juices are retained, and a lower-cost, lower-calorie meat product is obtained.

Sprouting is another way to utilize soybeans. It is estimated that 5 to 10 percent of the nutrient materials are leached out of soybeans during soaking, and the beans then become readily subject to microbial growth. Adding 1 teaspoon vinegar per cup of beans greatly reduces this microbial activity.

Dry soybeans keep well if stored in a cool, dry place. Like other beans, they should not be stored for more than three to five years, since many become hardened and will not take up water readily during soaking. This can generally be overcome by boiling the beans for one to two minutes before soaking. As a food storage item, soybeans may be used as a meat substitute with a wider range of use than meat only. Soybeans may be obtained from feed and seed stores, but only untreated soybeans can be used for food.

Note: Two soybean cookbooks are presently available from Soybean Digest, Hudson, Iowa 50643: Soybeans by P. S. Chen, $2.95, and The Soybean Cookbook by D. Jones, $1.45.

Dr. Johnson is chairman of the Department of Food Science and Nutrition at Brigham Young University.