Feasibility-study on the extrusion cooking for buckwheat flour

Using a twin-screw extruder, extrusion cooking of buckwheat flour were attempted to produce a product of puffed food in possession of high quality. Investigations were made to clarify the relationships between the quality of the extruded products and the extrusion cooking conditions, like differences among the screw patterns and so on. The results obtained are summarized as in the following: 1) Puffing of buckwheat flour has been rendered quite feasible by the practical use of the twin-screw extruder, however, the quality of the products is greatly influenced by the differences in the extrusion cooking conditions, such as, screw patterns, screw rotating speed and so on. 2) Concerning the screw pattern, the screw pattern III prepared by jointly combining the basic pattern with the kneading disk screw and reverse screw elements came to be regarded as one of the fittest extrusion cooking conditions owing to the results of the microscopic observations of the internal structure as well as the confirmation of the physical and chemical characteristics of the puffed products. 3) Concerning the rotating speed of the screw, under the present conditions of feed rate, water addition, and barrel temperature, the rotating speed of 200-250rpm was fixed to be the fittest one due to the results of the minute considerations paid to the uniforming, puffing rate and hardness of the products and so on. 4) At the extrusion cooking process, under the conditions of high temperature and intensive pressure, an extremely big shearing force comes inevitably upon the materials, which is powerful enough to render the buckwheat flour smashed, and enough to make it reduced into a micromolecular level. Therefore, it is assumed that the internal frictional heat which is to be brought forth due to the above described shearing action, makes it possible to gelatinize the starch within a quite short lapse of time