Abstract The determination of critical point in rheological-fractal models for most of the food gel systems and polymer viscoelastic systems are based on the point of 95% or 90% value of the storage modulus in linear viscoelastic region. It is not a precise method because the modulus during linear-nonlinear viscoelastic transition region are not always monotonous decreasing. Therefore, there is an urgent need for a more stable and precise approach to determine the critical point, making the scaling behavior calculation closer to the physical truth. This research studied on a typical food system, acid-induced peanut protein isolate (PPI) gel, trying to put forward a new critical point for isotropy food gel and non-newton polymer systems. Result shows that when the increasing higher harmonic reaches a certain value, the corresponding strain could be regarded as a new critical strain point. The image of the microstructure captured by confocal laser scanning microscope (CLSM) was used to calculate the actual fractal dimension, which was 2.3517. It was demonstrated that the fractal dimension calculated from rheological fractal model using the new critical strain obtained from the Fourier transform analysis is closer to its actual value (2.3517).

中文翻译：

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流变分形模型中各向同性凝胶的新临界点

摘要 大多数食品凝胶系统和聚合物粘弹性系统的流变分形模型中临界点的确定是基于线性粘弹性区域储能模量的95%或90%值的点。这不是一种精确的方法，因为线性-非线性粘弹性过渡区的模量并不总是单调递减。因此，迫切需要一种更稳定、更精确的方法来确定临界点，使缩放行为计算更接近物理事实。本研究以典型的食品体系——酸诱导花生分离蛋白（PPI）凝胶为研究对象，试图为各向同性食品凝胶和非牛顿聚合物体系提出一个新的临界点。结果表明，当增加的高次谐波达到一定值时，相应的应变可以看作是一个新的临界应变点。共聚焦激光扫描显微镜 (CLSM) 捕获的微观结构图像用于计算实际分形维数，为 2.3517。结果表明，使用从傅里叶变换分析获得的新临界应变，从流变分形模型计算出的分形维数更接近其实际值（2.3517）。