EFFECT OF BLANCHING AND UNBLANCHING ON RHEOLOGICAL PROPERTIES OF SWEET-POTATO BREAD

The effect of blanching and unblanching on rheological properties of sweet-potato bread, and textural effect at different substitution levels (10%, 20% and 30%) were investigated. The proximate analysis, functional properties and rheological properties were carried out on the flour; the data’s obtained from the results were subjected to Analysis of variance. Result showed that there was no significant difference in the protein, fat and carbohydrate content of sweet potato flour, but there was significant difference (P?0.05) in the ash, moisture and crude fiber. There was no significant difference (P?0.05) in the bulk density of the sweet-potato flour. The result also showed that the protein and ash of sweet-potato bread decreased significantly (P?0.05) with increased proportion of sweet potato flour. The substitution of sweet-potato flour into wheat flour affected the rheological and textural properties of wheat flour; the rate of water absorption of the wheat flour increased as sweet-potato substitution levels increased this was due to high starch content of sweet potato. Also, the dough stability time of the substituted sweet potato flours was lesser than that of the wheat flour. The 10% substitution level had the highest dough consistency (525BU). In addition, the sensory evaluation showed that there was significant difference between the organoleptic properties of wheat bread to that of substituted breads. 10% blanched sweet-potato bread had the highest consumer acceptability, while the 30% unblanched had the lowest rating due to appearance and hardness.