Neurotoxins in a vetch food: Stability to cooking and removal of gamma-glutamyl-beta-cyanoalanine and beta-cyanoalanine and acute toxicity from common vetch (Vicia sativa L) legumes

Because the neurotoxic common vetch (Vicia sativa L.) legume seems to have come into some use in man's diet, we have investigated, using Pico-Tag analysis, the stability of the vetch neurotoxins to cooking. When heated in water at 100 degrees C for 3 h, gamma-glutamyl-beta-cyanoalanine (gamma-gluBCA) cyclized extensively to form pyroglutamic acid and beta-cyanoalanine (BCA). By contrast three specimens of common vetch seeds containing 0.42-0.74% gamma-gluBCA and 0.01-0.03% BCA retained these principles without loss. A modified cooking procedure replacing the broth during cooking with fresh water and washing the seeds well yielded cooked seeds without detectable neurotoxins. A nutritional study confirmed that the toxins responsible for causing weight loss and mortality in chicks were removed. Lengthy steeping in water at room temperature also effectively removed the neurotoxins from dehulled split seeds but incompletely from intact seeds. These procedures improve the quality of common vetch seed as a source of protein for man.