Abstract:
Despite nutritional advantages, the functional quality of cereal foods tends to decline when fortified with
legumes. Traditional African cowpea-fortified sorghum foods were evaluated using instrumental and
descriptive sensory analyses. Two sorghum cultivars, NS 5511 (tannin-type) and Orbit (non-tannin-type)
were fortified with cowpea (70:30 ratio). Fortification reduced uji (fermented thin porridge) pasting peak
viscosity and cool paste viscosity by up to 23% and 12%, respectively, probably as a result of starch content
being reduced. NS 5511 injera (fermented thin flatbread) stiffness increased by up to 25%, probably due to
a reduction in tannin content. Orbit injera stiffness reduced by up to 22% probably because increased
protein content reduced starch retrogradation. Fortification increased the firmness of Orbit ugali
(unfermented stiff porridge) by 45% and 17% as assessed by TA-XT2 Texture Analyser and the descriptive
sensory panel, respectively. There was a 20% decrease in instrumental firmness of NS 5511 ugali as
a result of fortification, which was not detected by the sensory panel. Fortification had generally no effect
on the stickiness of ugali. Fortified ugali had a characteristic cowpea flavour. Principal component
analysis (PCA) of ugali sensory attributes indicated a 30% variation due to the presence of cowpea. Most
of the variation (47%) was attributed to sorghum cultivar. Sensory panel analysis concerning ugali
firmness and stickiness correlated positively with the instrumental texture analysis. Fortification with
cowpea affects texture and taste of traditional African sorghum foods, the extent to which largely
depends on the sorghum cultivar concerned. Instrumental texture analysis relates well with human
perception of sorghum food texture and can rapidly predict the effects of fortification with legumes on
such foods.
