Quality assessment of flour and bread from sweet potato wheat composite flour blends

Abstract

This study was to assess the quality of the flour and bread produced from sweet potato wheat composite flour blends. Matured and freshly harvested sweet potato (Ipomea batatas L.) was obtained from a local market in Akure, Nigeria. The tubers were thoroughly washed, peeled, washed again, drained, chipped, oven dried, milled, sieved and packaged. Five blends were prepared by homogenously mixing sweet potato flour with wheat flour in the percentage proportions of: 0:100, 5:95, 10:90, 15:85 and 100:0 (PF: WF) and later used to bake bread. Chemical, microbiological and physical properties of the composite flour and bread were examined. Semi-trained Panelists were assigned to assess the bread samples as well. The results of the proximate composition showed that the protein contents of the flours ranged from 1.44-12.44%; fat, 0.37-1.55%; carbohydrate, 69.69-80.92% and the protein contents of the bread samples ranged from 10.15-12.44%; fat, 4.36-4. 88%; carbohydrate, 80.44-105.47%. The flour samples had sodium content of 1.85-40.42 mg/ 100 g; calcium, 2.71-17.14 mg/ 100 g; potassium, 160.02-175.12 mg/100 g; selenium, 0.006-0.620 mg/ 100 g, while bread samples had sodium, 46.86-550.77 mg/ 100 g; calcium, 3.59-6.63 mg/ 100 g; potassium, 162.42-388.75 mg/100 g; selenium, 0.19-0.27 mg/ 100 g. Pasting properties showed that flour had breakdown (38.33-60.76 RVU) and setback values (82.86-173.50 RVU). The microbiological results of the flour ranged from 1.0×10³ to 7.0× 10³ cfu/g (bacteria) and 1.0× 10⁴ to 8.0× 10⁴ sfu/g (fungi) while for bread, 1.0× 10³ to 4.0×10³ cfu/g (bacteria) and 1.0×10⁴ to 8.0×10⁴ sfu/g (4.5×10⁴). No visible growth was recorded for E. coli. and Coliform bacteria. The bread loaf weights ranged from 450 to 500 g; loaf volume, 1171.73-1239.84 cm³ and specific loaf volume, 2.48-2.62 cm³/g. There is no significant difference in the crust colour, crumb holes, stability, elasticity, firmness, shape regularity and appearance of the samples. No panelist showed a total dislike for the taste of any of the samples. All the qualities evaluated did not significantly (p≤ 0.05) affect the acceptability and preference of the samples. Hence, it was concluded that wheat flour could be substituted with sweet potato flour up to 15% level in bread making which will still retain much of the physicochemical and sensory properties.

Keywords: Panelists, Pasting, Microbiological, Nutritional and Sensory properties