Isolation and Some Physicochemical Characteristics of isolated starch from two Nigerian varieties of African yam bean (Sphenostylis stenocarpa).

Abstract

The physicochemical properties of starch samples isolated from two Nigerian varieties of African yam bean (Sphenostylis stenocarpa) cowpea seeds were evaluated and studied. Starch yields were 47.1, 45.9 and 54.6g/100g seed weight for cream seed coat, brown seed coat varieties of African yam bean (AYB) and cowpea seeds, respectively. Cowpea seeds had significantly (p.0.05) higher starch but lower amylose contents than the AYB starches. Chemical analysis showed that AYB starches contained 0.1-0.2% protein, 0.3-0.4% lipid, 0.1% crude fibre and 0.1% ash, respectively. The AYB starches had
irregular shape that varied between oval to kidney shaped granules with mean sizes of 24.8} 3.2ƒÊm. Swelling power of the AYB and cowpea starches increased more rapidly at temperatures between 80-950C. Significant (p<0.05) varietal differences were observed in the solubility
patterns of the AYB starch samples within the temperature
range of 70-950C. Significantly (p< 0.05) higher percentage AYB and cowpea starches were solubilized at 80-950C than at 60-780C. The Brabender viscosity patterns showed a stable hot paste viscosity and a tendency for retrogradation.