Quality characteristics and sensory evaluation of cookies produced from composite blends of sweet potato (Ipomoea batatas L.) and wheat (Triticum aestivum L.) flour

Abstract

Cookies hold an important position in snack foods due to the variety in taste, crispiness and digestibility. Composite flours have better nutritional quality and would be highly desirable for the production of nutritious cookies. A study was carried out to develop cookies from the flour of sweet potato (Ipomoea batatas L.) and wheat (Triticum aestivum L.) and to evaluate the quality characteristics of the product. The mature sweet potatoes (cv. Wariapola Red) were procured from the commercial growers. Tubers were washed, peeled, cut into thin slices of 1 mm thickness and dried in the sun until the pieces were quite brittle. The dried chips were milled, passed through a 250 µm sieve and packed in air tight containers. Different composite blends of wheat flour and sweet potato flour were mixed in the ratios of 100:00, 80:20, 60:40, 40:60, 20:80 and 00:100. The nutritional analysis of sweet potato flour confirmed that it contains 2.3% protein, 9.4% dietary fibre and 85.5% soluble carbohydrates. Physical characteristics such as thickness, volume and spreading factor of the cookies decreased from 0.969 to 0.910 cm, 41.66 to 30.41 cm3 and 6.43 to 5.61, respectively, with increasing of sweet potato flour. The moisture, ash, fibre and soluble carbohydrate content increased significantly (p<0.05) from 1.33 to 1.37%, 2.07 to 2.4%, 2.14 to 8.7, and 80.86 to 85.97%, respectively, while protein content decreased significantly (p<0.05) from 7.04 to 6.22 with the increase in sweet potato flour from 0 to 100% of the composite flour for cookies. The sensory analysis showed that the cookies supplemented with 40% sweet potato flour were well acceptable in terms of colour, texture, taste and overall acceptability compared to other treatments. The mixture of 40% sweet potato flour and 60% wheat flour was successful for the formulation of composite cookies with better nutritional and organoleptic qualities within the universally accepted standards. The outcome of this research can be used as valuable information for the development of high fibre low gluten sweet cookies.