CHAPTER VI LEGUMES (Leguminosa) The legumes,1 or pulses, as they are called in England, stand next in importance to cereals among vegetable foods. They include beans in great variety, chick peas, peas, lentils, peanuts and a few other plants. They have been in use for so many hundreds of years and in so many countries that their origin is lost in antiquity. In China, India, northern Africa and other countries bordering on the Mediterranean Sea, they have formed an important part of the food of the common people for centuries. The plants of this family all have a characteristic papilionaceous or butterfly-shaped flower, and the seed grows in pods, containing sometimes few and sometimes a large number of individuals. Many of these plants are broad-spreading trees, which yield fruit entirely inedible for man, but most of those bearing edible fruit are low and herbaceous. Perhaps the most interesting characteristic of the family is, that many of the plants not only furnish a valuable food, but at the same time actually increase the fertility of the soil in which they are grown. This is due to the fixation of atmospheric nitrogen by the bacteria working unceasingly in the laboratories of the root nodules. It is only within the last seventy years that these facts in regard to the soil-fixation of nitrogen2 have been understood, although the practice of plowing under cow peas, clover and similar crops has been common for many years. Beans and peas mature rapidly, and therefore can be grown in the northern countries, as three or four months only are needed to bring them to full maturity. They are cultivated as garden 1 U. S. Dept. Agri., Farmers' Bull. No. 121. 2 U. S. Dept. Agri., Farmers' Bull. No. 315. crops, and have the advantage of not requiring any special kind of soil and indeed they will not refuse to grow and produce a fair crop on comparatively poor soil. This is largely due to the fact that they can avail themselves of a double supply of nitrogen— that which is contained in the soil as nitrites, nitrates and ammonia, and that which is collected from the air by the root nodules. Since protein food is usually expensive it would seem that in beans and other legumes we have found a cheap and abundant source of this kind of nutrient, and to a certain extent this is true, and beans have been extensively utilized for this purpose. It happens, however, that the protein exists in the legumes in the form of legumin with but little albumin. As has been pointed out by Voit, vegetable foods in general are less completely digested than animal foods, and this legumin is acted on mainly by the ferments which work in alkaline solutions, especially in the lower part of the alimentary system. On this account, then, beans are not readily digested in the stomach, although they are absorbed by the intestines. Nutritive Value Numerous experiments1 have been made to find out to what extent the protein of beans, peas, etc., is actually utilized as a nutrient in the human system. Some of these experiments seemed to indicate that there was a much greater waste of protein than when meat or wheat was used as food, but later results show that, with certain limitations and precautions, the protein of the legumes is fairly well digested. The legumes do, however, require more work by the digestive tract than many other foods. If beans or peas are ground before being cooked, the absorption of protein is more complete. It is also well established that if they are combined with other foods, and do not form too large a proportion of the diet, the nutriment is much more completely utilized than when they are used alone. In comparison with other vegetable proteins, the legume proteins are less well utilized.2 1 Human Foods and Their Nutritive Value, Snyder, p. 72. Jour. Biolog. Chem., Vol. 10, p. 457. The flatulence that is often occasioned by the use of a diet consisting largely of beans is probably caused by the breaking up by bacteria in the intestine of the germ of the bean, giving rise to a considerable quantity of the hydrocarbon, methan (CH4). Legumes as Food It is true that beans form an admirable and cheap addition to the food of persons engaged in manual labor, and persons exposed to severe weather, for in lumber camps and mining regions they are used in great quantities and with little discomfort. Under such conditions, a pound of baked beans per person a day produces no ill effects. People of sedentary habits, however, are not able to digest large quantities of leguminous foods, and whenever these foods are used an abundance of other nutrients should be eaten at the same time. Says Hutchinson, in speaking of the pea and bean,1 “As a cheap and efficient method of supplementing the deficiency of nitrogen in a purely vegetable diet, however, their use is strongly to be recommended, and it is a pity that they are not more largely taken advantage of by those to whom economy is of importance, for unquestionably the pulses are among the cheapest of foods, and a given sum will yield more protein, if invested in these, than in any other way." As the legumes when ground into flour furnish a more digestible food than when used whole, it is rather remarkable that this product is not more generally placed on the market. BEANS The bean on account of the numerous ways in which it can be prepared for food, and because it is so readily grown, is one of the most important of the legumes. It is believed that beans were cultivated by the Indians of both North and South America, 1 Food and Dietetics, p. 224. and we read of the Algonquins having one or two varieties of pole beans. Champlain speaks of planting the "Brazilian bean" in the region of the Kennebec, and bean flour is mentioned as having been in use among the Aztecs. All the beans of the genus Phaseolus, to which most of our common beans belong, are distinctly American plants. Beans may be grown for use as "snap" or "string" beans, as fresh or green beans, or they may be allowed to dry and be kept for winter use. Composition The amount of starch and protein in some of the common edible beans is as follows: The protein of beans is called legumin, and consists chiefly of phaseolin, and a small quantity of phaselin. Cooking The process used in cooking beans is of greater importance than is the case with most other vegetables. Young, absolutely fresh string beans can be thoroughly softened in from one to one and a half hours' boiling. The Germans pack string beans in salt, and thus cure them by a process in which lactic fermentation similar to that used for sauerkraut, occurs. They are then soaked out and freshened with water before using. Shell beans, which must also be fresh, should not be overcooked, or they will lose their fine flavor and become yellowish brown. The addition of butter, after the vegetable is cooked, improves the flavor and increases the food value of the product. Lima beans and kidney beans are often put upon the market canned, but the greatest demand is for "baked beans," which are frequently flavored with "tomato sauce," molasses, pork, etc. It is a question whether some of the so-called "baked beans" on the market should really bear this label, as the product differs so decidedly in method of preparation and quality from the domestic article. In the cooking of dried beans it is advisable to use a little baking soda in the water, as the soda helps to saponify the waxy material which coats the beans and is apt to seal the hilum so as to prevent the absorption of water and the consequent swelling of the beans. It is the common household practice to soak the beans for at least eight hours before boiling. The food is made more digestible if the skin which contains much indigestible cellulose is removed before cooking. This can be readily done by boiling with a small amount of baking soda, and then washing in cold water. The main requirements for cooking dried beans are, to soften the cellulose so that the beans can be easily masticated and thus render them more accessible to the digestive enzymes, to so cook the protein as that it shall be digestible and palatable, and finally to swell the starch grains. Experiments show that soft water is much more suitable for use in cooking beans and other legumes than hard water; rain or cistern water is the best, although of course there is no objection to the use of distilled water. The reason for preferring soft water is that the lime of hard water forms insoluble compounds with the proteins of the legumes, and then no amount of cooking will soften them. It has been universally conceded that long cooking at a moderate temperature develops the flavor of beans and most effectually |