| Abstrakt: |
Grits and flour extrusion is a relatively simple operation. Nevertheless, understanding the transport mechanism and property modifications which occur during the operation, is quite complex. Analysis of the effects produced on the material properties, through those methods that better describe the transformations produced, and the correlation of these "indicators" or responses with the process variables, would allow a better interpretation of the process as well as the selection of operation conditions to keep in mind so as to obtain the desirable characteristics in the product. In the present study, the effect of feed moisture, extrusion temperature and screw speed as well as compression ratio on corn flour properties, was evaluated through the following parameters or responses: feed rate, specific consumption of mechanical energy, specific volume, expansion, water solubility and amylogram. According to the results, feed moisture is the most relevant in modifying the properties, whereas the relative importance of temperature and compression ratio depend on the property being analyzed. Thus, for example, for specific consumption of mechanical energy, compression ratio is more important, while for expansion and specific volume, temperature is the most important. On the other hand, solubility appears to be the property that best describes changes involved during processing of the sample, while specific volume and specific consumption of mechanical energy--although being less efficient--also turn out to be very useful responses. |
