Cereal Chem. 71:247-253   |  VIEW ARTICLE


Influence of Extrusion Conditions on Extrusion Speed, Temperature, and Pressure in the Extruder and on Pasta Quality.

J. Abecassis, R. Abbou, M. Chaurand, M.-H. Morel, and P. Vernoux. Copyright 1994 by the American Association of Cereal Chemists, Inc. 

A fully instrumented pasta press was used to analyze the effects of experimental parameters (hydration, temperature, and shearing) on the pasta-making process and on quality characteristics of spaghetti. The rotational speed of the screw determined the flow rate of the extruder and influenced the extrusion speed, as did the open surface of the die. The differential speed (ratio between the shortest and longest strands during the same extrusion time) was decreased by the presence of a trefilette at the end of the screw. From an energy viewpoint, the procedure was very susceptible to the variation of parameters. For instance, the average specific mechanical energy transferred to the product for pasta extrusion was about 70 kJ/kg, but it could vary in a 1:5 ratio according to the extruding conditions, especially dough hydration and dough temperature, which both determine dough viscosity. These two parameters also had a great effect on pressure in the barrel and at the die. The presence of a pre-die seemed to exert a greater influence on the running of the screw, especially the fill rate and pressure at the end of the screw, than did the extruding conditions at the die level. Production factors were found to have little influence on the color of pasta; however, they did affect the cooking quality. Increases of the amount of hydration of the semolina and of the rotational speed of the screw enhanced cooking quality. A large open surface of the die improved the surface condition of cooked products but decreased the viscoelastic properties. An excessive increase of pasta temperature during extrusion appeared to be the main factor in the degradation of cooking quality. Therefore, a control of pasta temperature at the die was proposed as the simplest method to guarantee the quality of finished products.