This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Legumes rank next to cereals in importance as vegetable food. In middle and northern Europe among legumes peas are preferred, but in Mediterranean countries the use of beans and lentils predominates. In this country both peas and beans are extensively eaten, the lentil very little. Owing to the exceedingly leathery external envelope which they possess when old, legumes are very indigestible unless cooked for a long time, and if dried they require previous prolonged soaking in cold water, for drying diminishes their size and makes them extremely tough. Fresh legumes contain much water, and in percentage composition resemble the cabbage. They also contain much protein, carbohydrates, and a little fat. The proteid substance v. Liebig called "plant casein," from its resemblance to milk casein. It differs from the proteid gluten of grains and pea and bean flour and will not form dough or make bread. The percentage of protein in legumes exceeds that of the best beef (M. H. Abel). Although the legumes contain so large a percentage of protein, it is by no means all assimilated. Hoffman found that nearly one half of the protein of lentils passed off in the feces, being unabsorbed.
Strümpell found that 40 per cent of the protein of whole beans - i. e., with the skins intact - is undigested; but when made into flour only 8.2 per cent of protein was unabsorbed, the latter corresponding with the digestibility of meat protein.
Legumes are liable to induce intestinal fermentation, with excessive and often annoying production of gas (methan), hence they are not available as the sole article of diet. If eaten as an exclusive food, eighteen ounces of dried peas or beans, making six pints of thick soup, would have to be consumed daily (M. H. Abel).
Dried or "split" peas have had the external envelope removed, and they may be made into nutritious purees. The tough external coats of old peas may often be found wholly unaltered in the feces.
According to Parkes, a pound of peas contains 168 grains of starch, and about 6.5 per cent of this food is wasted in the alimentary canal.
Fresh very young green peas, petit pois, are easily digested, and may occasionally be allowed in a convalescent dietary, but old and tough legumes require more mastication even than meat.
The legumes are often cooked with pork, which raises the percentage of fat in this form of food and adds to their nutritive value. Baked beans are cooked in this way, and also pea soup; the swelling starch granules mingle with the melting fat of the pork and make the dish more palatable as well as much more digestible than when this fat is added to meat in the form of croquettes or mince, when it merely smears the outside of the larger particles of food.
Erbswurst, or pea sausage, was introduced some years ago in the German army. It was invented in 1870 by a cook named Griinberg, and the German Government bought the secret of its preparation. It is a cooked food composed of pea meal mixed with fat pork and salt, so treated as to prevent the decay of legumin. It is highly nutritious, for the peas contain a large proportion of nitrogenous as well as starchy material, and the fat furnishes energy, but as a diet it soon becomes monotonous, and not infrequently produces flatulence and diarrhoea, for which the legumes are noted. The flatulence is caused by liberation of sulphuretted hydrogen from a substance called legumin.
Erbswurst may be quickly made into soups. It figured largely in the Franco-Prussian War, and was known as the "iron ration." A powdered "pea soup" may now be obtained which is composed of powdered peas and extracts of beef with salts and herb extracts for flavouring. A three-and-a-half-ounce package contains in grammes: proteids, 21; fats, 17.25; carbohydrates, 46.5. It is excellent for army service in the field.
Composition of some Prepared Military Pea Foods (Woodruff)
" as first used..
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Dried pea soup (1)
" " " (2)
Kopf's " " (used by the English army)....
S. P. Sharpless.
Penzoldt has succeeded in obtaining predigested vegetable albumin by the following receipt:
Finest pea meal................................... 250.0 grammes.
Pepsin........................................... 0.5 gramme.
Salicylic acid...................................... 1. 0 "
Mix and let stand at ioo° F. for twenty-four hours; strain.
Haricots or kidney beans constitute a very serviceable article of diet, being one of the cheapest and best of all the pulses. These beans must be thoroughly soaked until swollen and soft before boiling, and should be only eaten when wholly tender. Their flavour is heightened by the addition of a little onion, parsley, or other aromatic vegetable, and their nutritive value is increased by cooking them with pork.
Fresh, young, and tender string beans are very digestible.
Young, fresh Lima beans are wholesome and very nutritious, but if old they are indigestible.
The red bean of the tropics, which is largely used in the Mexican army ration, is less prone to cause diarrhoea than the dry domestic white bean; but it has a more tender skin, is therefore less easily transported, and it absorbs moisture so rapidly that it is liable to ferment.
The frijole is a small, flat, reddish-brown bean much eaten in Mexico and neighbouring portions of the United States.