Effect of Extrusion Variables on the Hydrogen Cyanide and Haemagglutinin Content of Extruded Blends of Cassava Products and African Yam Bean

Abstract

High quality cassava flour (CF) and African yam bean (AYB) flour  were blended together , also pregelatinized, shreaded cassava chips (Ighu) and AYB flour were blended separately using feed ratios of 0.54:99.46, 20:80, 50:50, 80:20, 99.46:0.54 (AYB/CF or AYB/Ighu) The extruder screw speed and the moisture content of the blends were also varied. The samples were extruded using a single screw extruder. Hydrogen cyanide content and haemagglutinin contents of the extrudates and the raw samples were determined. The data obtained were statistically analyzed using response surface methodology. The results obtained showed that there were no significant difference (p > 0.05) in the linear, quadratic and interaction for moisture content and screw speed, but there were significant difference in the linear and quadratic effects of feed composition on the hydrogen cyanide of the samples. The results also showed that extrusion cooking affected the hydrogen cyanide content of AYB/Ighu blends more than the cassava flour/AYB blends. The values obtained were below the Industrial Standard for cassava and cassava products. The residence time of the feed material had significant effect on the reduction of haemagglutinin content of the end products. The model for AYB/ Ighu was adequate more than that of AYB/CF.

Keywords: Hydrogen cyanide, haemagglutinin, extrusion, cassava, African yam bean