1.1 BACKGROUND OF STUDY
In Nigeria, a lot of under exploited plant food crops with promising nutritional potentials
exist. Lima bean is one of the under exploited food crops with nutritional and food industry
processing potentials. Lima bean is among the lesser known legumes in the southern part of
Nigeria. The food crop is one of the traditional staples that in the most recent decades was
neglected. However, the neglect is attributed to difficulties in production, processing,
preparation, utilization and negative image attached to it as “poor man’s food”. Lima bean
has longer cooking time, especially as compared with other legumes. This longer cooking
time phenomenon is a particular drawback for its cultivation and food use. It is imperative
to investigate the positive attributes of this important food legume mostly its nutrient
potentials. Legumes as protein-rich crops are important source of protein for human food
and animal feed. In 1972-1974, legumes contributed 7% to the total protein supply
worldwide (FAO, 1982). Generally, legumes contain 17-25% protein (about double that in
most cereals) except soybean which contains about 40% protein (Enwere, 1998). Legumes
are usually consumed in combination with cereals such as rice, maize, millet, and sorghum.
They are sometimes combined with roots and tubers such as yam, cassava, potatoes, and
cocoyam or consumed with plantains and bananas. Studies have shown that legume proteins
complement cereal and roots to provide an ideal source of dietary protein of vegetable
origin for human beings (Latham, 1997). This is because cereal protein which is deficient in
lysine and rich in methionine and cystine complement legume proteins which are rich in
lysine and poor in methionine and cystine (Bressani, 1975; Segal and Fawcelt, 1976).
Despite the high nutrient content of legume seeds, their utilization is impaired by some
inherent constraints such as the presence of several antinutrients and food toxicants.
The type and concentration of these antinutrients vary in different legumes (Leiner, 1980). Lima
bean has the highest content of hydrogen cyanide 10-312mg/100g) depending on the
variety. The hydrogen cyanide content of other major legumes range from 0.5mg/100g to
2.3mg/100g (Ologhobo et al; 1984).