BACKGROUND:Okra is a vegetable that is widely grown around the world. Okra mucilage contains a high mucus concentration that can be useful for supporting the swallowing process. Although the extensional rheology of okra mucilage is essential to its flow, its extensional viscosity has not received much attention. OBJECTIVE:Using a filament stretching rheometer, the extensional viscosity of the mucilage in okra was examined. The Giesekus model is also used to predict this parameter. METHODS:The okra mucilage with different concentrations was extracted from fresh okra. The extensional viscosity was measured using a filament breakup apparatus. The diameter of the liquid bridge was measured by a laser micrometer and it was also observed by a high-speed camera. A rotational rheometer was used to measure the shear viscosity. In addition, the master curves for the shear viscosity were plotted to eliminate the influence of solvent and shear rate and evaluate the influence of concentration on the elasticity of okra mucilage. The okra mucilage shear and extensional viscosity were predicted using the Giesekus model. RESULTS:Every sample of okra mucilage exhibits shear thinning behavior. Additionally to having a high extensional viscosity that is hundreds of times higher than its shear viscosity, okra mucilage also exhibits stretching phenomena. The master curves demonstrated that the pseudoplasticity of the okra mucilage increased along with the concentration. The rheological behavior of the mucilage in okra can be explained by the Giesekus model. CONCLUSIONS:Okra mucilage’s shear viscosity exhibited shear thinning behavior and a strong extensional viscosity that was significantly higher than its shear viscosity. The shear and extensional viscosity of okra mucilage can be described and predicted using the Giesekus model.

中文翻译：

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使用 Giesekus 模型研究和预测秋葵粘液的拉伸粘度

背景：秋葵是一种在世界各地广泛种植的蔬菜。秋葵粘液含有高粘液浓度，可用于支持吞咽过程。尽管秋葵粘液的拉伸流变学对其流动至关重要，但其拉伸粘度并未受到太多关注。目的：使用长丝拉伸流变仪检测秋葵粘液的拉伸粘度。Giesekus 模型也用于预测此参数。方法：从新鲜秋葵中提取不同浓度的秋葵粘液。使用断丝装置测量拉伸粘度。液桥的直径用激光测微仪测量，也用高速相机观察。使用旋转流变仪测量剪切粘度。此外，绘制剪切粘度的主曲线以消除溶剂和剪切速率的影响，并评估浓度对秋葵粘液弹性的影响。使用 Giesekus 模型预测秋葵粘液剪切和拉伸粘度。结果：每个秋葵粘液样品都表现出剪切稀化行为。除了具有比其剪切粘度高数百倍的高拉伸粘度外，秋葵粘液还表现出拉伸现象。主曲线表明，秋葵粘液的假塑性随着浓度的增加而增加。秋葵粘液的流变行为可以用 Giesekus 模型来解释。结论：秋葵粘液的剪切粘度表现出剪切稀化行为和明显高于其剪切粘度的强拉伸粘度。可以使用 Giesekus 模型描述和预测秋葵粘液的剪切和拉伸粘度。