2017 Volume 45 Issue 2 Pages 91-99
Food bolus cohesiveness plays an important role to suppress miss-swallowing in swallowing disorder. The cohesiveness of masticated particles can be enhanced by binding liquids, which often represent high spinnability similarly as oral saliva does. Thus, in addition to shear viscosity, the extensional viscosity is important to control the bolus swallowing. Using a capillary thinning extensional viscometer, this study measured the extensional viscosity of natural okra, yam, and kelp mucilage in addition to whole saliva and a thickener solution for liquid care foods. The mucilages showed very high extensional viscosity, which was two or three orders of magnitude higher than the shear viscosity. The rheological characteristics for shear and extensional flow were found to be described by a Giesekus model approximately. The results obtained here can be applied to simulate the bolus swallowing numerically and to improve care foods for swallowing disorder.
