Wittek Patrick, Zeiler Nicole, Karbstein Heike P, Emin M Azad
Institute of Process Engineering in Life Sciences, Chair of Food Process Engineering, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
Foods. 2021 Jan 6;10(1):102. doi: 10.3390/foods10010102.
The high moisture extrusion of plant proteins is well suited for the production of protein-rich products that imitate meat in their structure and texture. The desired anisotropic product structure of these meat analogues is achieved by extrusion at high moisture content (>40%) and elevated temperatures (>100 °C); a cooling die prevents expansion of the matrix and facilitates the formation of the anisotropic structure. Although there are many studies focusing on this process, the mechanisms behind the structure formation still remain largely unknown. Ongoing discussions are based on two very different hypotheses: structure formation due to alignment and stabilization of proteins at the molecular level vs. structure formation due to morphology development in multiphase systems. The aim of this paper is, therefore, to investigate the mechanism responsible for the formation of anisotropic structures during the high moisture extrusion of plant proteins. A model protein, soy protein isolate, is extruded at high moisture content and the changes in protein-protein interactions and microstructure are investigated. Anisotropic structures are achieved under the given conditions and are influenced by the material temperature (between 124 and 135 °C). Extrusion processing has a negligible effect on protein-protein interactions, suggesting that an alignment of protein molecules is not required for the structure formation. Instead, the extrudates show a distinct multiphase system. This system consists of a water-rich, dispersed phase surrounded by a water-poor, i.e., protein-rich, continuous phase. These findings could be helpful in the future process and product design of novel plant-based meat analogues.
植物蛋白的高水分挤压非常适合生产在结构和质地上模仿肉类的富含蛋白质的产品。这些肉类模拟物所需的各向异性产品结构是通过在高水分含量（>40%）和高温（>100°C）下挤压实现的；冷却模头可防止基质膨胀并促进各向异性结构的形成。尽管有许多研究关注这一过程，但结构形成背后的机制在很大程度上仍然未知。目前的讨论基于两种截然不同的假设：蛋白质在分子水平上的排列和稳定导致的结构形成与多相系统中形态发展导致的结构形成。因此，本文的目的是研究植物蛋白高水分挤压过程中各向异性结构形成的机制。以大豆分离蛋白这种模型蛋白为原料，在高水分含量下进行挤压，并研究蛋白质-蛋白质相互作用和微观结构的变化。在给定条件下可实现各向异性结构，且其受物料温度（124至135°C之间）的影响。挤压加工对蛋白质-蛋白质相互作用的影响可忽略不计，这表明结构形成不需要蛋白质分子的排列。相反，挤出物呈现出明显的多相系统。该系统由富含水的分散相和贫水（即富含蛋白质）的连续相组成。这些发现可能有助于未来新型植物基肉类模拟物的工艺和产品设计。
