Extrusion processing of plant proteins to design meat analogues: Analysis of structuring mechanisms

Plant-based meat analogues, which are intended to imitate the characteristic mouthfeel and texture of meat, have become very popular in the last few years. This can be attributed to a change in consumers behaviour caused by health, ethical and sustainability concerns related to meat consumption. These products can be produced by high moisture extrusion (HME), where a protein-rich raw material (protein content > 50%), such as soy protein isolate (SPI) or wheat gluten, is processed at high water content (> 40%). In the extruder, raw material and water are continuously mixed, heated, sheared, and then pressed through a cooling die. This processing leads to the formation of anisotropic structures in the extrudate, which create a meat-like mouthfeel and texture. Although there are many studies on HME, most of the findings, such as on the influence of independent process parameters on the anisotropic structures, are empirical, material- and machine-specific and not transferable. Thus, there is still insufficient research on how the formation of the anisotropic structures takes place in the extrusion process and it is unclear how the product properties are influenced by the raw material selection and process setup. The aim of this work is to extend the mechanistic understanding of the structure formation in the HME of plant-based protein-rich raw materials. A mechanistic understanding would allow the process design and control to be specifically adapted to the requirements of the product properties.