In reactive extrusion, thermomechanical stresses are explicitly applied to biopolymeric food materials to achieve the desired functionality and structure in the final food product. However, control of the extrusion process is very challenging due to strong interactions between mass, energy and momentum transfer, coupled with complex physicochemical transformations of the material, which govern its thermomechanical properties. With other words, material structure is not only the result but also a part of the process, as it affects the development of material properties and therefore processing conditions along the extruder.<br/>For understanding structural changes in extrusion, the processing conditions must be characterized on a local level by in-depth analysis of the thermal and mechanical stress profile together with the mixing characteristics in extrusion processing. Furthermore, material properties and their relation to the local processing conditions play crucial role on structural changes in extrusion processing. Therefore, the material properties (i.e. mainly reaction and rheological properties) under extrusion conditions must be characterized. Such information is essential to provide a mechanistic understanding necessary to move away from purely empirical approaches in designing complex biopolymeric systems.<br/>In this talk, we present a research approach and tools that practically enable us to gain an improved process understanding at a mechanistic level. The approach is based on the fractionation of the process into interrelated sections. These sections can then be investigated in defined manner using various experimental and numerical tools, including rheometry (inline slit-die rheometer, offline closed cavity rheometer), computational fluid dynamics simulation, and inline infrared sensors.

Rheology and modeling of complex food systems in reactive extrusion

253rd National Meeting (2017)

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