The estimation of vicine and convicine in fababeans (Vicia faba L.) and isolated fababean proteins.

Abstract

AbstractA specific method of analysis for each of the pyrimidine glucosides, vicine and convicine, is described. This involves extraction by ethanol, evaporation, separation on t.l.c. and quantitative ultraviolet spectrophotometry. Using this method mature dehulled fababeans were shown to contain on average 0.73% vicine and 0.30% convicine on a dry matter basis. No significant variation was found between varieties. The glycosides seem to be associated to the protein bodies in the raw bean, and are absent from the hull. The total content of vicine + convicine in isolated fababean proteins ranged from 0.07 to 2.0%. The highest content was found in a protein fraction produced by air‐classification of dry milled fababeans. The lowest content was found in proteins isolated from a watery extract either by precipitation with acetic acid or by diafiltration. Protein isolates produced by direct ultrafiltration have contents of about 0.60%. The ratio vicine:convicine was found to be relatively constant in the raw beans (average 2.5), but varied from 1.4 to 3.0 in the protein isolates, thus indicating a different reaction of vicine and convicine to conditions during the processing of the fababean. It is the opinion of the authors that the etiology of favism is still controversial as far as vicine and convicine are concerned.