Technological Properties of Wheat/Trifoliate Yam (Dioscorea dumetorum) Hardened Tubers Composite Flours

Abstract

The ability of trifoliate hardened-yam flours to partially substitute wheat flour in food formulations was assessed. Three varieties of hardened-yam flour were incorporated in wheat flour in proportions of 0, 10, 20, 30, 40, and 50% (w/w). Samples were evaluated for protein content, Zeleny sedimentation index, Hagberg falling number, functional properties (WAC, WSI, and OAC), and some rheological properties including dough rupture pressure (P), extensibility (L), stability (P/L), and deformation energy (W). Results showed that trifoliate hardened-yam flours do not have acceptable baking properties as pictured by the low Zeleny sedimentation index and the low Hagberg falling number. Protein quality (Zeleny index, 31) of wheat flour helped to compensate gluten deficit of yam flours, but the amylasic activity determined by the Hagberg falling number could not be adjusted, which resulted in a loss of extensibility (L) of the paste at 10% substitution. Multivariate analysis of experimental data regrouped wheat flour and all wheat/hardened-yam treated with kanwa composite flours in one homogeneous cluster. Although wheat/hardened-yam treated with kanwa composite flours had physicochemical and functional properties similar to wheat, the inadequate diastasic activity makes them inappropriate for bread making, marking the strongest influence of that parameter.