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

• African Yam Bean has a smaller and narrower starch granules size distribution than potato.
• It displays a A-type crystalline pattern while potato starch displays a B-type.
• African Yam starches seem more stable than potato starch during hydrothermal treatments.
• It presents a low swelling and disintegration capacity than potato tuber starch.
• Under combustion its starch is degraded at higher temperature than potato 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 5.7 μ to 49 μ with a median at 19.5 μ. 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.