Legumes provide an important part of the world's protein requirements, as well as other nutrients, but they are underutilized as food. A major factor limiting expanded consumption is storage induced textural defects that prolong cooking time and demand correspondingly higher energy requirements for preparation. These defects, including the hard-to-cook phenomenon and hardshell, are initiated by structural and compositional factors but can be at least partially controlled by storage and processing conditions. Structural components implicated include seed coat, cell walls, middle lamella, starch granules and membranes while, compositionally, proteins, carbohydrates, phytate, polyphenols and lignin may also be important. Methods of texture measurement of legumes, including mechanical, physical and sensory properties are reviewed. The most commonly held hypothesis for the mechanism of the hard-tocook defect states that beans fail to soften after exposure to high temperature and humidity storage because the increased water activity potentiates phytase which hydrolyzes phytate, rendering it no longer capable of chelating the Ca" and Mg++ ions of the middle lamella and, hence, undissoluble. More recent evidence, however, provides potential roles for lignification, starch gelatinization and perhaps other mechanisms depending upon conditions. The possibility of a nonenzymutic as well as an enzymatic route is raised and thoughts presented on a course of action for future research. Protein Lys in. Soybemns Dry bean. Pemnuts Legume. , totml Wheat Corn Rice C e r e m l s . totml 2 5 . 8 0 0 11,500 2,500 39.800 4 2 . 6 0 0 2 5 , 8 0 0 2 4 , 0 0 0 9 2 , 4 0 0 1.805 eo5 105 2.715 815 775 935 2 . 5 2 5
