Antinutritive Factors in Eleven Legumes and Their Air‐classified Protein and Starch Fractions

Abstract

ABSTRACTPin milting and air classification of starchy legumes enriched the protein content of the light fraction to 49–75%, within the range of defatted soybean flours and protein concentrates. The levels of trypsin inhibitors, hemagglutinating activity, saponin, phytic acid and fiber were high in navy bean flour and the levels in the protein fractions of navy and northern beans greatly exceeded those of soybean flour. Potential nutritional problems in the air‐classified protein fractions of other legume species include trypsin inhibitor in lima bean and chickpea and saponin in lima bean, cowpea and lentil. Fababean and mung bean flours and protein fractions were comparatively lower in each antinutritive factor but fababean products contained vicine and convicine.SUMMARYTHE EFFECTIVENESS of the pin milling and air classification of starchy legumes in the separation of protein and starch fractions has been amply demonstrated (Sosulski and Youngs, 1979). A previous study showed that the protein fractions also contained higher levels of oligosaccharides than the original flours while the starch fractions were depleted in sugars. In the present investigation, the concentrations of trypsin inhibitor, hemagglutinating activity and phytic acid in the protein fractions were up to 300% higher than the original flour while saponins and dietary fiber also tended to segregate with the protein. The starch fractions from most of the nine legume species and biotypes were substantially detoxified by the dry milling process. The protein fractions of navy and northern beans contained particularly high levels of essentially all of the antinutritive fractions and may require extensive processing if food uses of the products are anticipated. On the other hand, mung bean and fababean products were much lower than soybean flour in most antinutritive factors although the fababean protein fraction was enriched in vicine and convicine.