Natural toxicants in selected leguminous seeds with special reference to their metabolism and behaviour on cooking and processing

Abstract

A brief survey is presented of the most relevant heat labile and heat stable natural toxicants found in syobean and dry bean (Phaseolu~ vulgaris). Investigators, aided by rapid development of biochemical instrumentation and techniques, have concentrated upon the elucidation of the chemistry of proteinaceous protease inhibitors and glycoproteins with lectin character. It appears that the tow M.W protease inhibitor (abt. 10000) in raw legume meal is in part responsible for the pancreatic hypertrophy observed in rats and chicks fed raw legume meal as the principal source of dietary protein, whilst the large M.W. lectin (abt. 100000) from raw navy bean has been found to be lethal to conventional but not to germfree quail. No real explanation has been advanced for the poor growth observed when these small animals feed on protein from raw legumes.The conventiat temperatures and heating times used to inactivate these inhibitors are discussed. There is a lack of scientific information as to the low levels of inhibitors or toxicants that would be tolerated in heated legumes and the heattreatment required to achieve acceptable low levels of toxicants commensurate with the achievement of optimum palatability and preservation of the maximum nutritional value of the legume protein.

RESEARCH NOTE: HEMAGGLUTINATING ACTIVITY of LECTINS IN SELECTED VARIETIES of RAW and PROCESSED DRY BEANS

“…The effects of various processing methods on the hemagglutinating activities of lectins of dry bean varieties used in this study are summarized in Table 2. The values obtained for the hemagglutination activity of the whole dry beans were within the ranges reported for several legume species (Nachbar and Openheim 1980;Stein 1976; Thompson et al 1983). In the present study, these values for the whole and dehulled bean lectins ranged from 128-512 X 10" and 128-1024 x 10" units/g of bean flour, with mean values of 307 X lo4 and 576 X lo4 unitdg, respectively.…”

Composition, protein quality, and toxins of seeds of the grain legumesGlycine max,Lupinusspp.,Phaseolusspp.Pisum sativum, andVicia faba

“…The lectins (also called phvto-haema· gIutinins) have been the subject of extensive research which has been reviewed by Stein (1976) .…”

Damage to nutritional value of plant proteins by chemical reactions during storage and processing

“…The invention of cooking made available (and more palatable) to the human race, many plant foods not readily eaten by other animals. Prof. Boulter and Dr. Stein are dealing with toxicity in legume-seed proteins (Boulter, 1976;Stein, 1976); the use of cooking to destroy this toxicity is the biggest single benefit derived from cooking. Protein denaturation by heat also, in general, improves digestibility by the gut proteases.…”