2B. LEGUMES
The grain of food legumes—also known as grain legumes, or pulses—is second in
importance only to cereals as a source of human and animal food. The greatest
variety of legumes is found in the tropics and subtropics; in India and some other
countries legumes provide the only high protein component of the normal diet.
There are more than 18,000 species of legumes, of which about 30 are important
as food crops. Despite the enormous importance of legumes as protein sources, only
soybeans and groundnuts have received much attention from plant breeders or
research workers.
Many of the under-exploited crops with potential as human and animal food are
members of the Leguminosae plant family—the Tepary Bean, Mat (Moth) Bean,
Rice Bean, Winged (Four-angled) Bean, Lupin, Camel Thorn, Bambara Groundnut
and Leucaena are just a few of the examples, some of which are described in Section
The average protein content of legume grain is about 26%, though some have up
to 60%, and pulses have been described as “the poor man’s meat”. Although many
of the legume seeds are deficient in certain essential amino-acids (cystine and
methionine in particular), these are normally present in cereals which are often eaten
together with legumes to form a balanced diet.
The seed of many legumes is poisonous, containing certain alkaloids that must
be broken down by cooking before they are eaten. If the seed is sprouted, as in
China where the practice is an ancient tradition, not only is this problem averted but
also large quantities of vitamins are released which are not available from the dry
seed.
Some of the legumes, such as soybeans, groundnuts and winged bean, not only
have high protein content but are also rich in oil; these crops are the so-called
“oilseed legumes”.
The ability of legumes to produce, or “fix”, Nitrogen in nodules on their roots is
another reason for their major influence on food production. Cowpeas, for example,
150 TONY WINCH
2G. “Under-exploited Crops”, pages 266–287.