Single screw extrusion of cassava starch was evaluated as a pre-treatment for the enzymatic hydrolysis of the extrudate and fermentation to yield alcohol. The acid concentration, barrel temperature and moisture content showed that all the variables were significant. Increasing acid concentration or barrel temperature induced starch depolymerisation with a higher water solubility index and lower water absorption index. At 20 and 24% moisture contents the cold paste viscosity decreased. As a result of the addition of acid during extrusion cooking the degree of starch hydrolysis resulted in low hot paste viscosity. Acid concentration was significant in the production of reducing sugars. At concentrations above 0.024 N, as the temperature increased, the reducing sugar content also increased. Nevertheless, at concentrations below 0.024 N, the reducing sugar content showed the opposite result. The best yield of alcohol obtained from the extruded starch was 98.7% (0.56 g of ethanol/g starch), which, on average, was 5.7% and 6.8% higher than that obtained from starch extruded without acid and from starch gelatinized by the conventional method, respectively.
In bread making the wheat dough undergoes some degree of deformation in each step of the process. It is generally accepted that the baking properties of wheat flour dough are mainly due to the viscoelasticity of the gluten protein. Measurement of the rheological properties of dough gives valuable information concerning the quality of the wheat flour, the machining properties of the dough and the textural characteristics of the finished products. This technique uses a new apparatus (wheat gluten quality analyser&WGQA, C HANG, 1994) especially developed to evaluate the rheological properties of gluten by measuring the following parameters: resistance to extension (newton), extensibility (mm) and energy (joule). The test realized with the apparatus WGQA was carried out on wheat gluten isolated according to the A.A.C.C. (1995) method. Results obtained using the new technique showed high levels of correlation for maximum resistance to extension (R 2 =0.9018) and energy (R 2 =0.8824) between WGQA and standardized parameters obtained from Brabender Extensograph.