Physical quality characters of cookies produced from composite blends of wheat and sweet potato flour

A research study was carried out to develop cookies with good nutritional and physical quality from sweet potato flour and wheat flour and to evaluate the quality characteristics. The mature sweet potato (cv. Wariapola Red) tubers were washed, peeled, cut into thin slices of 1mm thickness, dried under the sun until the pieces were quite brittle, milled and sieved. Different composite blends of wheat flour and sweet potato flour were mixed in the ratios (w/w) of 100:00, 80:20, 60:40, 40:60, 20:80 and 00:100. Cookies were then prepared from separate mixtures following manufacturing procedures. Sweet potato flour was nutritionally analyzed and it contained 2.3% protein, 9.4% dietary fiber and 85.5% soluble carbohydrate, and therefore, sweet potato flour appeared to be suitable for a successful combination with wheat flour for the production of cookies. Physical characteristics such as thickness, volume, diameter and spreading factor of the cookies decreased from 0.969 to 0.910 cm, 41.66 to 30.41 cm3, 7.4 cm to 6.52 cm and 6.43 to 5.61 respectively while density of cookies increased from 0.474 g/cm3 to 0.652 g/cm3 with increasing of sweet potato flour up to 100%. The sensory qualities showed that the cookies supplemented with 40% sweet potato flour were well acceptable in terms of colour, texture, taste and overall acceptability. The mixture of 40% sweet potato flour and 60% wheat flour had been successful for the formulation of composite cookies with better physical, nutritional and organoleptic qualities within the universally accepted standards.