Functional Properties of Non-Wheat Flour Substitutes in Composite Flours. II. Amylolytic Susceptibility of Non-Wheat Starches

Abstract

Starches from tubers of some species of the genus Dioscorea (D. rotundata Poir.), D. alta. L., D. cayenensis Lam., D. esculenta (Lour.) Birk., roots of cassava (Manihot utilissima Pohl.), cormels of cocoyam (Xanthosoma sagittifolium Schott.), fruits of plantain (Musa paradisiaca L.) together with starches from sorghum (Sorgho ROF) and millet (SOUNA II) were tested for susceptibility of the ungelatinized granules to the action of bacterial α-amylase, fungal glucoamylase and malt diastase. Though all starches were found more resistant to enzymatic degradation when compared with starch extracted from the Canadian hard red spring wheat, considerable differences were observed between individual starches. Among non-cereal starches, cassava starch was found the most susceptible one, whereas large granule yam and plantain starches did not show any significant degree of digestion even after 48hours treatment with the enzymes.Scanning electron microscopy revealed that the mode of the enzymatic attack on the granules of cassava and cocoyam starch— both being composed starches, differed from that on cereal starch granules. The reduction of the diastatic activity of composite flours, in which wheat flour was replaced by less susceptible starches, reflected in a lower CO2 production in sucrose-free doughs during fermentation.