ABSTRACT

This study was conducted to compare the effect of blanched and unbianched processing method on orange-fleshed sweet potato as composite flour in confectionary production. Three genotypes of orange-fleshed sweet potato (OFSP) namely: CIP 199004.2, CIP 199005.11 and CIP 440216 was used and the roots collected was washed with tap water, peeled under water to reduce enzymic browning and striped using the Chipping machine, each of the striped samples was shared into two portions; one portion was left unbianched, washed, drained and oven dried while the other portion was blanched in hot water (90°C) for 5 minutes, drained and oven dried. The dried samples were milled using hammer mill and later sieved (0.2mm) into flour. Physicochemical properties, mineral, antinutritional factors and functional properties of both the blanched and unbianched OFSP flours were determined using standard methods. Wheat flour which served as reference was also analyzed. The results of the unbianched OFSP flour samples showed that the dry matter content (90.25 — 91.63%), protein content (6.22 — 7.68%), carbohydrate content (82.16 — 85.61%), fiber content (1.72 — 2.96%), ash content (2.12 — 2.73%) and fat content (6.53 — 9.97%) levels of the samples were significantly different from that of the blanched OFSP flour samples. While the proximate composition of the control (wheat) is as follows: dry matter content (89.34%), protein content (12.73%), carbohydrate content (80.94%), fiber content (1.90%), ash content (2.30%) and fat content (2.17%) levels. There was a significant difference in the water absorption capacity (4.64 — 5.15g!g) and oil absorption capacity (2.26 — 3.43g/g) of the blanched OFSP flour samples relative to that of the unblanched flours. The blanched OFSP flour samples had higher water absorption capacity (4.64-5.15g/g) than the unblanched OFSP flour samples (2.68-3.26g1g). The 13-carotene content, calcium, iron and zinc content of unblanched OFSP flour samples were higher (3.48 — 5.64 tgIg; 14 — 22mg/g; 0.62 — 0.84mg/g and 0.24 — 0.40mg/g respectively) than that of the blanched OFSP flour samples. The antinutrients in unblanched OFSP flour samples had slightly higher (phytate:-1.04 -1.2% and tannins:-0.20 - 0.28%)) than that of the blanched OFSP flour samples (phytate:-0.46 - 0.68% and 0.12- 0.15%). The significant variations of the OFSP flour samples may be due to varietal differences and processing methods. There was no difference between the unblanched OFSP cake products, except in CIP 199005.11 at 100:0 substitution level and CIP 440216 at 70:30 substitution level; while for blanched OFSP cakes, Only CIP 199005.11 at 100:0 and 70:30 substitution levels and CIP 440216 at 50:50 substitution level were well accepted of all the blanched OFSP cakes. None of the blanched chin chin of the OFSP varieties was liked by the panelists. The unbianched chin chin color of CIP 199004.2 at 50:50 substitution level and CIP 440216 at 70:30 and 50:50 substitution levels was liked by the panelists. The flour of OFSP has a potential of being a good substitute/composite for wheat flour.