Structural and physicochemical characterization of Sphenostylis stenocarpa (Hochst. ex A. Rich.) Harms tuber starch.

Several characteristics of African Yam Bean tuber starch (AYB) were studied and compared with that of a well-known native potato starch (P). The diameter of AYB granules ranged from 5.7μ to 49μ with a median at 19.5μ. During its pasting, AYB exhibited a low peak of viscosity in accordance with its low granules swelling and disintegration capacity. The gelatinization temperature of AYB was 75.2°C while that of P was 60.4°C. AYB was observed to be more stable during thermo-gravimetrical Analysis. Its degradation peak was observed at 308°C while that of P was 303°C. The X-ray diffraction analysis revealed that AYB belongs to the A-type crystalline group instead of C-type as claimed for several legumes starches. The stability of AYB and its capacity to structure starch-water systems make this resource an interesting ingredient for new food and non-food products.