Evaluation of bread made from composite wheat-sweet potato flours

Wheat flour was replaced with 5-20% sweet potato flour (SPF) prepared from solar dried slices of an orange flesh Mexican cultivar (cv Nylon) and the physical properties of the dough and bread were studied. Crust and crumb color and appearance and bread porosity were evaluated by a sensory panel. On a dry weight basis, the SPF was composed of 7.4% protein, 1.6% fat, 13.7% crude fiber, 1.9% ash, 40.6% reducing sugars, 35.2% N-free extract, and 17 mg/100 g carotenoids, and 81.5% of the flour had a particle size of 0.149 mm or less. As SPF percentage increased, water absorption capacity and firmness of bread increased, while farinograph and alveograph indices (P, L and W) and specific volume decreased. Water absorption capacity was highly correlated with L, specific volume and firmness. Developing time predicted 96.5% of the variability in firmness. Dough stability was highly correlated with alveograph parameters and inversely correlated with firmness. High negative correlation was found between extensibility, L, and firmness. Physical and sensory analyses showed that substitution of wheat flour with 5-10% sweet potato flour yielded acceptable doughs and breads. All sensory properties (except crust color) differed significantly between control breads and those supplemented with 15 and 20% SPF. All breads with SPF differed from control breads in porosity.