Effects of extrusion conditions on physical and nutritional properties of extruded whole grain red sorghum (sorghum spp)

Abstract

In order to analyze the effects of extrusion temperature (T: 164, 182, 200 C) and grits moisture content (g/100 g sample) (%M: 14, 16.5, 19) on textural and physicochemical properties of red sorghum extrudates, whole grain flour was extruded according to a factorial experimental design. The higher values for specific mechanical energy consumption (1006.98 J/g) and expansion (3.36) were obtained at 164 C–14%M and for sensorial hardness at 164 C–19%M. While for specific volume, the highest value (10.41 cm3 /g) was obtained at 200 C–14%M. Water solubility and water absorption were directly related with T and inversely with M. Microscopic observation of the samples indicates that the greatest cooking degree was obtained at 200 C–4%M and the lowest at 164 C–19%M. Extrusion at 182 C–14%M allows obtaining an expanded product with good properties. Proximal composition did not show statistically significant differences with raw sample. Extruded sample showed a 25.4% reduction of available lysine and a 31% increase in protein digestibility.