Helen T Zewdie and M Naushad Emmambux
University of Pretoria, South Africa
Posters & Accepted Abstracts: J Food Process Technol
The combination of underweight in children and overweight in adults, frequently coexisting in the same family, is a relatively new phenomenon in developing countries. Extrusion cooking may help to improve the nutritional quality and rheological properties of extrudates depending on the extrusion cooking conditions. Producing high and low glycemic index ready-to-eat products would be useful to tackle protein energy malnutrition and diabetes respectively. The gluten free Ethiopian indigenous grain, teff (Eragrostis tef), apparently has higher level of micro- and macronutrients than that of barley, wheat and sorghum and has the potential to be used in these ready-to-eat products. Extrusion cooking experiments were conducted using a twin screw extruder by varying feed moisture conditions (either 25% or 40%) and last two zones in-barrel temperatures (either 90 or 140℃). Functional properties, pasting viscosity, in-vitro protein and starch digestibility, soluble and insoluble dietary fibres were studied. High feed moisture extrusion cooking significantly reduced the bulk density, water absorption capacity, pasting viscosity and insoluble dietary fibre. Whereas, low feed moisture extrusion cooking significantly increased the water solubility index, soluble dietary fibre, in-vitro protein and starch digestibility. The feed moisture had greater effect to produce high and low GI ready-to-eat porridges. High feed moisture during extrusion cooking probably acts as plasticizer and reduces the shear force in the barrel. This may result in the reduction of degree starch depolymerisation. The increase in viscosity could be from the increase in soluble dietary fibre and the lower extent of starch depolymerisation during high moisture extrusion cooking.
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