Removal of favism-inducing factors vicine and convicine and the associated effects on the protein content and digestibility of fababeans (Vicia faba L)

Ingestion of fababeans is associated with precipitation of the haemolytic disease favism in certain glucose-6-phosphate dehydrogenase-deficient humans. Hence their incorporation into weaning foods has not yet been practised. Few, if any, attempts to detoxify fababeans have so far been made. The present investigation has evaluated the effects of a series of treatments designed for vicine and convicine extraction and hydrolysis followed by oxidation of their pyrimidine moieties (divicine and isouramil). The effects of seed germination and oxidative treatment by hydrogen peroxide have also been examined. Extracts of treated samples were assayed for residual vicine and convicine. Toxicity was monitored by the changes in vitro of reduced glutathione (GSH) of red blood cells (RBCs) from Sprague Dawley rats deliberately made deficient in glutathione reductase activity to mimic favism-susceptible human RBCs. Treatments of whole cotyledons resulted in recovery of 59-93% vicine and 50-70% convicine originally present in the seeds. Treatments of fababean powders, however, were capable of lowering the vicine content by 94-100% and convicine content by 100%. Germinated seeds showed a drop in vicine content of 86% and their hydrogen peroxide treatment 91-93%. Convicine was totally absent in germinated and oxidised seeds. The results of toxicity assays were concomitant with vicine and convicine analyses. Protein content of original fababean powders was well recovered (up to 94.00%) and its digestibility was almost complete (99.34%).