Evaluation of the chemical composition, functional and pasting properties of four varieties of Nigerian sweet potato [Ipomoea batatas L. (Lam.)] flour

Abstract

Data on nutritional composition, functional and pasting properties of food ingredients are of importance in food formulations. In this work, flours were prepared from four varieties of Nigerian sweet potato. Chemical composition, functional and pasting properties of the flours were determined using standard procedures. The moisture contents ranged between 6.5% and 10%, which are below 15% specified for flour samples. This study showed that Orange Fleshed Sweet Potato (OFSP) had the highest protein (2.9%) and Yellow Fleshed Sweet Potato (YFSP) had the least (2.3%). This study also showed that OFSP flour had the highest β-carotene content and YFSP had the least indicating that pro-vitamin A is more concentrated in OFSP than other varieties. The amylose content ranged between 21% and 21.7%. The values obtained for OFSP, YFSP, and White Fleshed Sweet Potato (WFSP) are not significantly different from each other but significantly higher than the value obtained for Purple Fleshed Sweet Potato (PFSP). The bulk density ranged between 0.8g/ml and 0.9g/ml indicating easy sinkability and dispersibility. Water absorption capacity ranged between 58% and 83%. The oil absorption capacity ranged between 31% and 51%. The solubility and swelling capacities ranged from 7% to 11%, and 1.2% to 1.7%, respectively. The pasting temperature/ time ranged between 780C (3.9 min.) and 830C (4.8 min.) indicating that the flours have easy to cook properties. The peak viscosity of the sweet potato flours ranged between 46.9RVU and 86 RVU and it indicates that WFSP will form paste easily than OFSP. The setback values ranged between 3.8 RVU and 21 RVU. The WFSP have the highest tendency to retrograde and the OFSP having the least tendency. The final viscosity ranged between 13 RVU and 82.2 RVU. Results indicate that the WFSP will form a better gel than OFSP. The above results indicate that the flours have good functional and pasting properties that make them useful for application in food products formulations.