SP - Food and Biosciences, Soft Materials Science, Gothenburg, Sweden.
Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
J Texture Stud. 2017 Dec;48(6):507-517. doi: 10.1111/jtxs.12264. Epub 2017 May 2.
People who suffer from swallowing disorders, commonly referred to as dysphagia, are often restricted to a texture-modified diet. In such a diet, the texture of the fluid is modified mainly by the addition of gum or starch-based thickeners. For optimal modification of the texture, tunable rheological parameters are shear viscosity, yield stress, and elasticity. In this work, the flow properties of commercial thickeners obtained from major commercial suppliers were measured both in shear and extensional flow using a laboratory viscometer and a newly developed tube viscometry technique, termed Pulsed Ultrasound Velocimetry plus Pressure Drop (PUV + PD). The two methods gave similar results, demonstrating that the PUV + PD technique can be applied to study flow during the swallowing process in geometry similar to that of the swallowing tract. The thickeners were characterized in relation to extensional viscosity using the Hyperbolic Contraction Flow method, with microscopy used as a complementary method for visualization of the fluid structure. The gum-based thickeners had significantly higher extensional viscosities than the starch-based thickeners. The rheological behavior was manifested in the microstructure as a hydrocolloid network with dimensions in the nanometer range for the gum-based thickeners. The starch-based thickeners displayed a granular structure in the micrometer range. In addition, the commercial thickeners were compared to model fluids (Boger, Newtonian, and Shear-thinning) set to equal shear viscosity at 50/s and it was demonstrated that their rheological behavior could be tuned between highly elastic, extension-thickening to Newtonian.
Thickeners available for dysphagia management were characterized for extensional viscosity to improve the understanding of these thickeners in large scale deformation. Extensional deformation behavior was further explained by using microcopy as corresponding technique for better understanding of structure/rheology relationship. Moreover, the major challenge in capturing human swallowing process is the short transit times of the bolus flow (<1 s). Therefore, the ultrasound-based rheometry method; PUV+PD which measures the real-time flow curve in ∼50 ms was used in addition to classical shear rheometry. The two methods complimented each other indicating that the PUV+PD method can be applied to study the transient swallowing process which is part of our future research, where we are studying the flow properties of fluids in an in vitro swallowing tract.
患有吞咽障碍的人，通常被称为吞咽困难，他们通常被限制在质地改良的饮食中。在这种饮食中，液体的质地主要通过添加胶或淀粉基增稠剂来改良。为了达到最佳的质地改良效果，可调流变学参数是剪切粘度、屈服应力和弹性。在这项工作中，使用实验室流变仪和一种新开发的管流变技术，即脉冲超声速度加压降（PUV+PD），测量了来自主要商业供应商的商业增稠剂的流动特性，包括剪切和拉伸流动。这两种方法得出了相似的结果，这表明 PUV+PD 技术可以应用于研究与吞咽通道几何形状相似的吞咽过程中的流动。使用超双曲收缩流法对增稠剂进行了与拉伸粘度相关的特性描述，并用显微镜作为补充方法，用于可视化流体结构。胶基增稠剂的拉伸粘度明显高于淀粉基增稠剂。流变行为表现在微观结构中，胶基增稠剂呈现出纳米级的水胶体网络，而淀粉基增稠剂呈现出微米级的颗粒结构。此外，将商业增稠剂与模型流体（Boger、牛顿和剪切稀化）进行了比较，这些模型流体在 50/s 时设定了相同的剪切粘度，并证明它们的流变行为可以在高度弹性、拉伸增稠到牛顿之间进行调节。
为了提高对这些增稠剂在大变形中的理解，对可用于吞咽障碍管理的增稠剂进行了拉伸粘度特性描述。进一步使用显微镜作为相应的技术，以更好地理解结构/流变关系，来解释拉伸变形行为。此外，捕捉人类吞咽过程的主要挑战是食团流动的短传输时间（<1 s）。因此，除了经典的剪切流变学之外，还使用基于超声的流变测量方法 PUV+PD，该方法在大约 50ms 内测量实时流动曲线。这两种方法相互补充，表明 PUV+PD 方法可以应用于研究瞬态吞咽过程，这是我们未来研究的一部分，我们正在研究体外吞咽通道中流体的流动特性。
