Abstract
The present study examined the relationship between rheological and swallowing characteristics of Liquid foods prepared by the addition of commercial thickening agents indispensable to meals for people with swallowing disorders.<SR>Rheological characteristics were studied for starch-based and guar-gum-based Liquid foods prepared, by the addition of thickening agents, to be of comparable hardness. For samples prepared to have yogurt-like hardness, the smaller the apparent viscosity (η app), or storage modulus (G'), the easier it was to swallow the sample. Videomanofluography was employed for examining bolus samples whose hardness was altered into three stages (equivalent to salad oil, mayonnaise and mashed potatoes, respectively) by the addition of thickening agents. Ultrasonic tomography was used on model boluses having mashed potato-like hardness, for studying the tongue movement at the time of swallowing.
These studies revealed how healthy people take food into their oral cavities, perceive the rheological/swallowing characteristics of the food, transform their tongues in order to create easy-to-swallow boluses, and control the driving force of their tongues so that the boluses can be passed onto the pharynx. The study results also implied that controlling the driving force of the tongue serves to keep constant the speed at which the bolus passes through the pharynx
