Physicochemical and functional characterization of yam starch for potential industrial applications

Yam is a significant and highly prized starchy crop in West and Central Africa, but largely underutilized industrially. Functional and physicochemical properties of starches extracted from forty-three varieties of Dioscorea rotundata, Dioscorea alata, Dioscorea dumetorum, Dioscorea cayenensis, and Dioscorea bulbifera were investigated for their potential industrial utilization. Water binding, swelling, gelation capacity, granule size, amylose/amylopectin, pasting characteristics, paste clarity, and syneresis were determined. Results showed that starches from D. rotundata, D. alata, D. cayenensis, and D. bulbifera had large starch granules (25-50 mu m) while D. dumetorum had small granules (7-12 mu m). There was variability in the starch granule shapes, which were mostly oval, round, and triangular. The least gelation concentration of the starches was between 4 and 16%. Paste clarity of the starches decreased as storage days increased and all the starches exhibited high syneresis indicating tendencies to retrograde on low storage temperature. There were differences in the pasting characteristics of the yam starches with D. rotundata and D. bulbifera having high peak viscosities compared to others. These differences in functional and physico-chemical properties of the yam starches are discussed as indicators of the various products for which they can be utilized in both food and non-food applications.