In the food industry, many food products experience extreme processing conditions of high temperature and high shear stresses. The measurements of sample behavior for water-based formulations above 100°C is extremely challenging due to changes in material composition from the boiling of volatile ingredients. We have developed a high-sensitivity, pressurized starch pasting cell (up to 5 bar) which utilizes a design free of mechanical bearings and seals, resulting in an order-of-magnitude improvement in torque sensitivity (1 μN.m in oscillatory and 10 μN.m in shear flows) compared to traditional pressure cells. A pressurized atmosphere in the cell suppresses boiling of the volatile components, allowing the characterization of the structure-property relationships of the sample over a range of testing conditions (-5 to 150°C) which simulate industrial processing and storage conditions. This cell is employed to investigate the pasting properties of a commercial starch dispersed in water. In-situ gelatinization of starch dispersions of varying starch particle weight fractions (ϕ) subjected to a high temperature (120°C) at elevated pressure and at a fixed shear rate is studied. A phase transition, from an initial flowable starch slurry to a paste, takes place during which the viscosity evolves by several orders of magnitude. Typical parameters associated with the viscosity evolution during gelatinization such as onset temperature, peak temperature, and peak viscosity are analyzed to probe the impact of high temperature on the gelation process and the rheological properties of the final starch paste. Furthermore, yield stresses of the final paste, measured at 120°C, are examined for varying ϕ through traditional rheological methods such as flow ramps, oscillatory shear, and stress growth, demonstrating the capabilities of this cell for studies of steady shear and nonlinear viscoelastic behavior of the starch pastes. The yield stress values are found to be in good agreement when comparing various testing methods. Yield stresses range from 0.25-6.5 Pa for ϕ between 0.05 and 0.15, with 0.05 being the minimum starch weight fraction for which there is any measurable yield stress. The yield stress and the paste viscosity both scale with starch particle weight fraction as (ϕ - ϕc )m , where ϕc = 0.04 as no yield stress is observed for ϕ ≤ 0.04. The exponent, m, for yield stress is found to be in the range of 1.15-1.4 depending on the analytical method used and the definition of yield stress while for peak and breakdown viscosities it is noted to be 1.6 and 1.1, respectively. The Herschel-Bulkley model is found to fit the flow curves well. The starch pastes are found to exhibit shear-thinning and significant thixotropic behavior. This article is protected by copyright. All rights reserved.

中文翻译：

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高温下淀粉分散体的流变学

在食品工业中，许多食品都经历了高温和高剪切应力的极端加工条件。由于挥发性成分沸腾导致材料成分发生变化，因此测量 100°C 以上水基配方的样品行为极具挑战性。我们开发了一种高灵敏度、加压淀粉糊化单元（高达 5 bar），该单元采用无机械轴承和密封件的设计，从而使扭矩灵敏度提高了一个数量级（振荡为 1 μN.m，振荡为 10 μN.m 在剪切流中）与传统压力传感器相比。电池中的加压气氛抑制了挥发性成分的沸腾，允许表征样品在模拟工业加工和储存条件的一系列测试条件（-5 到 150°C）下的结构-性能关系。该单元用于研究分散在水中的商业淀粉的糊化特性。研究了在高压和固定剪切速率下经受高温 (120°C) 的不同淀粉颗粒重量分数 (φ) 的淀粉分散体的原位糊化。从最初的可流动淀粉浆到糊状物的相变发生，在此期间粘度会发生几个数量级的变化。与糊化过程中粘度变化相关的典型参数，例如起始温度、峰值温度、分析和峰值粘度以探讨高温对胶凝过程和最终淀粉糊流变特性的影响。此外，在 120°C 下测量的最终糊状物的屈服应力通过传统流变学方法（如流动斜坡、振荡剪切和应力增长）检查不同的 ϕ，证明该单元具有研究稳定剪切和非线性粘弹性的能力。淀粉糊的行为。当比较各种测试方法时，发现屈服应力值非常一致。对于介于 0.05 和 0.15 之间的 ϕ，屈服应力范围为 0.25-6.5 Pa，其中 0.05 是存在任何可测量屈服应力的最小淀粉重量分数。屈服应力和糊状物粘度都与淀粉颗粒重量分数成比例为 (ϕ - ϕc )m ，其中 ϕc = 0。04 因为对于 ϕ ≤ 0.04，没有观察到屈服应力。发现屈服应力的指数 m 在 1.15-1.4 的范围内，这取决于所使用的分析方法和屈服应力的定义，而对于峰值粘度和击穿粘度，它分别为 1.6 和 1.1。发现 Herschel-Bulkley 模型很好地拟合了流动曲线。发现淀粉糊表现出剪切稀化和显着的触变行为。本文受版权保护。版权所有。发现淀粉糊表现出剪切稀化和显着的触变行为。本文受版权保护。版权所有。发现淀粉糊表现出剪切稀化和显着的触变行为。本文受版权保护。版权所有。