Local process conditions in the twin-screw extruder during the functionalization of highly concentrated protein systems

Plant-based, protein rich foods such as meat substitutes have become an indispensable part of the refrigerated shelves of the large supermarket chains. Consumers are turning to the substitute products not only for health, environmental or ethical reasons, but also because they can now imitate meat products well. In addition to taste and appearance, the mouthfeel, especially the bite into the fibrous structure, plays a decisive role. To produce meat substitutes with these product properties, the high moisture extrusion process is usually used. In the extrusion process, protein powders and water are fed into the extruder, conveyed by the rotation of the screws, kneaded, mixed and heated, and then structured and shaped through a cooled die. While in the early days of high moisture extrusion, the main focus of research was on the generation of meat-like structures, at present additional attention is being paid to "Formulation Engineering". Here, there is interest in transferring existing processes based e.g. on gluten or soy protein to other plant proteins. To simplify this step and thus save resources, a mechanistic understanding of the processes both in the screw section and in the die section of the extruder is necessary. ... mehrIn this conference post, we demonstrate how different numerical methods can help to obtain a better mechanistic understanding of the processes in the screw section of the extruder. For example, local temperature and shear rate peaks can be determined and thermal and mechanical stress histories can be recorded. Since the accuracy of numerical methods strongly depends on the complex rheological models that have to be implemented in the simulations, the rheological characterization of highly concentrated plant proteins will also be addressed.