Abstract Highly concentrated biopolymers are used in food extrusion processing. It is well known that rheo-logical properties of biopolymers influence considerably both process conditions and product properties. Therefore, characterization of rheological properties under extrusion-relevant conditions is crucial to process and product design. Since conventional rheological methods are still lacking for this purpose, a novel approach is presented. A closed cavity rheometer known in the rubber industry was used to systematically characterize a highly concentrated soy protein, a very relevant protein in extruded meat analogues. Rheological properties were first determined and discussed in the linear viscoelastic range (SAOS). Rheo-logical analysis was then carried out in the non-linear viscoelastic range (LAOS), as high deformations in extrusion demand for measurements at process-relevant high strains. The protein showed gel behavior in the linear range, while liquid behavior was observed in the nonlinear range. An expected increase in elasticity through addition of methylcellulose was detected. The measurements in the non-linear range reveal significant changes of material behavior with increasing strain. As another tool for rheological characterization, a stress relaxation test was carried out which confirmed the increase of elastic behavior after methylcellulose addition.

中文翻译：

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用闭腔流变仪分析高浓度蛋白质的复杂流变特性

摘要 高浓度生物聚合物用于食品挤出加工。众所周知，生物聚合物的流变特性对工艺条件和产品特性都有很大影响。因此，挤出相关条件下流变特性的表征对于工艺和产品设计至关重要。由于仍缺乏用于此目的的常规流变学方法，因此提出了一种新方法。使用橡胶工业中已知的闭腔流变仪来系统地表征高度浓缩的大豆蛋白，这是一种非常相关的挤出肉类类似物的蛋白质。首先在线性粘弹性范围 (SAOS) 中确定和讨论流变特性。然后在非线性粘弹性范围 (LAOS) 中进行流变学分析，由于挤压过程中的高变形需要在与过程相关的高应变下进行测量。蛋白质在线性范围内表现出凝胶行为，而在非线性范围内观察到液体行为。通过添加甲基纤维素检测到弹性的预期增加。非线性范围内的测量结果表明，随着应变的增加，材料行为发生了显着变化。作为流变学表征的另一种工具，进行了应力松弛测试，证实了添加甲基纤维素后弹性行为的增加。非线性范围内的测量结果表明，随着应变的增加，材料行为发生了显着变化。作为流变学表征的另一种工具，进行了应力松弛测试，证实了添加甲基纤维素后弹性行为的增加。非线性范围内的测量结果表明，随着应变的增加，材料行为发生了显着变化。作为流变学表征的另一种工具，进行了应力松弛测试，证实了添加甲基纤维素后弹性行为的增加。