ABSTRACT

This research studied the effect of supplementation of wheat flour with orange fleshed sweet potato flour on the quality of cookies. Flours from peeled and unpeeled OFSP were added to wheat flours at five levels of supplementation (90:10, 80:20, 70:30, 60:40, 50:50) to form composite flours used for analysis and production of cookies. Results of analysis of the raw materials (OFSP and wheat) showed variations in their proximate composition in which the OFSP had higher moisture and fibre than the wheat flour which had higher protein, fat, ash and carbohydrate. The addition of the OFSP flours caused increases in the functional properties of the composite flours including oil absorption capacity (1.367g/g to 2.00g/g), water absorption capacity (2.033g/g to 2.633g/g), emulsion capacity (54.9% to 75.68%) and wettability time (71.0secs to 113.33secs). But bulk density (0.546g/cm³ to 0.406g/cm³) and gelation temperature (94.67ºC to 85.33ºC) reduced. The variations were higher in the unpeeled OFSP supplemented composite flours. The addition of OFSP supplements impacted positively on the nutrient status of both the composite flours and the cookies. The protein, fat, and ash contents decreased slightly but significantly, while the fibre and carbohydrate levels increased significantly. There were slight but significant reductions in the mineral content of the OFSP supplemented cookies. Also, the water-soluble vitamins (B1, B2, B3, and B6) all reduced in the cookies while β-carotene content increased from 0.00 (wheat cookies) to 5.73µg/g and 7.13µg/g in the peeled and unpeeled OFSP supplemented cookies respectively. Notwithstanding, the variation in the nutrient status of the cookies, there were significant improvement in the physical properties of the cookies wherein the weight, thickness, volume and diameter all increased with the introduction of the OFSP. The results of bioavailability of calcium, iron and zinc showed variations in cookies at different supplementation levels. Higher increases of calcium were observed in the animals fed with unpeeled OFSP supplemented cookies with value of 80.01% to 80.79% as against 78.23% to 80.59% in the peeled OFSP puree supplemented cookies fed animals. The bioavailability of iron in the cookies diet to the animals was low, being in the range of 16.84% to 21.50%, but did not differ significantly (p>0.05) with that recorded for other iron sources. The level of absorbed zinc in the rat fed with OFSP supplemented cookies was higher (28.44% to 33.52%). It was also observed that zinc bioavailability was higher in the animals fed with unpeeled OFSP supplemented cookies diet. The cookies were also very acceptable to consumer panellists with mean acceptability range from 70.56% (6.35/9) to 79.44% (7.15/9). It was concluded that the supplementation of wheat flour with OFSP to enhance its nutrient status and utilization in production of cookies was feasible, successful, and with acceptable product