High-moisture extruded protein fiber formation toward plant-based meat substitutes applications: Science, technology, and prospect

Background: Recently, plant-based meat substitutes have generated considerable interest for their benefits in terms of environmental sustainability and personal health. High-moisture (above 40%) extrusion is an important technology for preparing whole-cut plant-based meat substitutes with meat-like fibrous structure and texture. However, it remains challenging on a more fundamental level to understand the interactions during extrusion processing related to the transition of the protein molecules or phase into fibrous structures, which is considered as a "black box" with scarce information inside.Scope and approach: Here, protein sources that can be texturized by high-moisture extrusion are summarized. Next, high-moisture extruded protein texturization theories are explained from three interdisciplinary subjects. Furthermore, technical points including extrusion conditions, screw configuration, and cooling die design are analyzed. Lastly, a comprehensive evaluation of high-moisture extruded plant-based meat substitutes is outlined. Key findings and conclusions: A wide range of protein sources from legumes, oilseeds, cereals, miscellaneous beans, vegetables, algae, fungus, and insects are available for high-moisture extrusion. There is increasing consensus that the dynamics of protein aggregation and phase separation determine the formation of fibrous structures during high-moisture extrusion. Protein fibrous structure formation mainly occurs from the die to the cooling zone through a "sub-layer transformation" cross-linking. A combination of simulation work with actual experiment requires additional focus and insight for the regulation and control of high-moisture extrusion processes. Comprehensive evaluation methods are necessary to compare plant-based meat substitutes with different animal meats.