The ripe seeds of pulses rank next to cereals in importance as vegetable foods. They are especially rich in nitrogen, the chief proteins being legumin or vegetable casein. They are also rich in starch, but deficient in fats. They are richer in salts than in cereals, especially in potash and lime, but poorer in magnesia and phosphates.
The leading points in the composition of pulses may be stated as follows: -
Rich in proteins.
Deficient in fats.
Rich in carbohydrates.
Contain much cellulose.
Rich in salts.
Dried peas, like dried beans, contain a large amount of nourishment. In this respect dried beans, dried peas, and lentils are practically equal, the peas and lentils containing rather less fat and more cellulose than the beans. Dried peas are not readily digested. Very special care is necessary in the cooking, so as to promote digestibility.
The protein present is rich in sulphur, which tends to produce sulphuretted hydrogen and similar compounds, so that a leguminous diet tends to cause flatulence. Pulses are rather indigestible on account of the leathery external envelope which they possess when old. Hence they require prolonged cooking in order to promote digestibility. They require to be cooked in soft water, since the lime and magnesia found in hard waters form insoluble compounds with legumin. An analysis of the chief pulses is given by Bauer as follows, the average composition of wheat being given for comparison: -
It will be seen from the above table that their nutritive value is considerable, especially as regards the amount of proteins. They are a cheap and efficient method of supplementing the deficiency of nitrogen in a vegetable diet, and on account of the large amount of proteins they contain, they are admirably adapted as food for the poorer classes. Their defects as compared with the cereals are their relative indigestibility, their unsuitability for breadmaking, and their less agreeable taste. About 6 per cent, of the ingested pea passes out unchanged, and starch cells giving a blue reaction with iodine are found in the faeces.
The pea nut is not a nut but a legumen. It resembles nuts in the large percentage of fat in its composition. It is used largely as a diabetic food, and it also enters largely into the composition of the patent food "Nutrose".