Protein content in legume seeds is governed both by genotype and by environment. Seed protein levels can vary across varieties of a given species and even among seeds on an individual plant. In general, however, food legumes contain 20-30% protein by proximate analysis (Table 2). The exceptions to this are soybean and winged bean, which contain up to 37 and 45% protein, respectively.

Legume proteins are primarily of two types: storage proteins, which account for approximately 70% of total seed nitrogen, and enzymatic, regulatory, and structural proteins, which are present for normal cellular activities, including the synthesis of storage proteins. Legume storage proteins are soluble in dilute salt solutions but insoluble in water and therefore fall into the classical globulin group of protein fractions. Legume protein types are further characterized by their sedimentation coefficients, which in most species approach 11S and 7S; these are commonly referred to as the legumins and vicilins, respectively. Most legumes contain both types of storage protein, but the proportion of the two types varies from species to species.

In terms of protein quality, as defined by an optimal proportion of amino acids required by humans, legume proteins are deficient in the

Table 2 Protein contents of food legume seeds


Protein range (% dry weight)

Broad bean

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