Advances in conversion of natural biopolymers: A reactive extrusion (REX)–enzyme-combined strategy for starch/protein-based food processing

Abstract Background The last decade has seen the extensive use of bio-based polymers from renewable resources in many fields, to facilitate a sustainable, effective and diversified development of human activities. However, the natural polymeric matrices have processing difficulties because of their complicated structures. The green method combing reactive extrusion (REX) and enzymatic action has been adopted for the efficient conversion and utilisation of these biomaterials in food, medicine, energy as well as other areas. Scope and approach This review aims to offer a panoramic overview of the development of food-related biopolymers such as starch, protein and the derivatives, using REX and enzyme as powerful and useful processes. The special advantages, critical issues, application cases and future developments of REX–enzyme strategy were thoroughly discussed. Key findings and conclusions New types of REX–enzyme synergies were illustrated with different mechanisms according to the enzyme or extruder type, substrate level and energy intensity in the reaction microenvironment. The multiple REX and enzymatic processes is popular but gradually improved to a simple co-extrusion process of enzymatic reactive extrusion (eREX). It requires a compatible reaction state of both enzyme and substrate for eREX under the same and balanced conditions. Furthermore, starch- and protein-based matrices are usually extruded with strong or limited enzymatic actions for producing general and functional foods.