The Variability of Free Amino Acids and Related Compounds in Legume Seeds

Abstract

Legume seeds are an important source of protein for humans and domestic animals. The Leguminosae contain more than 700 genera and 25,000 species, yet fewer than 20 of these are grown as major world crops. The nutritional value of legume seeds is frequently less than ideal, however, because their proteins contain lower concentrations of certain “essential” amino acids than do animal proteins. The fact that “free” amino acids frequently constitute more than 10% of the weight of legume seeds is often overlooked when considering their nutritional value, as free amino acids tend to be lost in traditional methods of cooking. Toxins, such as the alkaloids, cyanogenic glycosides, and certain of the “nonprotein” amino acids are also found in the seeds of numerous legumes. An understanding of their nature, concentration, and distribution is necessary if we are to exploit the great potential food reserve represented by the thousands of legume species that have never been brought into cultivation or used for the improvement of established crop species. During the past few years we have studied the free amino acids in the seeds of more than 1500 legume species representing 300 of the 700 known genera, and in time propose to make a complete survey of the family. For ease of retrieval, we are assembling analytical data on magnetic tape in a computer bank. Complementary information on the presence of alkaloids, cyanogenic glycosides, toxic amino acids, and physiologically active amines in these seeds is also being accumulated, and we are presently seeking funds to extend this work and determine the protein content and composition of the seeds of this unique collection.