Hydration kinetics of direct expanded tef flour breakfast cereals in water and milk
Hydration kinetics of tef flour breakfast cereals extruded at barrel temperatures of 110, 130, and 150°C was investigated by hydrating them in water and whole milk at 25°C (±1°C). The normalized Weibull model described the rehydration characteristics of the extrudates in water and milk adequately (R2 = 0.98–0.99). Water absorption rate was significantly (P < 0.05) influenced by barrel temperature where extrudates processed at 150°C barrel temperature exhibited high water absorption rate followed by those extruded at 130 and 100°C, respectively. Hydration rate and equilibrium moisture content were higher for samples hydrated in water than those in milk. In view of the values of the shape parameter β, the hydration process is predominantly controlled by diffusion (β = 0.40–0.51) for samples extruded at 110°C whereas external resistance to mass transfer dominated (β = 0.60–0.73) those extruded using 150 and 130°C. Extrudates processed at 130 and 150°C exhibited better hydration characteristics. Thus, these temperature ranges could be used to produce extruded products from tef.
Effects of operating conditions on oil loss and properties of products obtained by co-rotating twin-screw extrusion of fatty meal: preliminary study
Abstract The effects of some operating conditions on oil loss and physical properties of products obtained by doughs containing almond flour extruded in a co-rotating twin-screw extruder were investigated. The results showed that the lowest loss of oil was obtained at low percentages of dough moisture and high values of screw speeds. The extrusion parameters that greatly influenced the structural characteristics of extruded products were dough moisture and screw speed. In particular, the best results were obtained by extruding at 36% dough moisture and 200 rpm screw speed. The operating conditions suitable to obtain both a low oil loss and a good product structure were low percentages of dough moisture and high values of screw speed and extrusion temperature.
Die wisselwerking tussen ekonomiese en konstitusionele hervormings in Suid‐Afrika
Abstract This article deals with the interplay between economic and constitutional reforms in South Africa. Historical and contemporary forces which obtain in these spheres are taken into consideration after which a number of conclusions are drawn.