ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 23, 2015 ABSTRACT When we eat the swallowing is mainly an involuntary process. However, for an increasing number of the population the actual swallowing causes problems. The effect of elasticity on swallowing was thus evaluated. Edible model fluid foods were developed and the rheological properties were evaluated. The study indicated positive effects of fluid elasticity on the ease of swallowing for patients suffering from dysphagia. INTRODUCTION Swallowing is a highly unconscious process. We prepare a bolus by chewing and mixing with saliva and as soon as we initiate swallowing, it is an involuntary process 1 . However, for an increasing proportion of the population the actual swallowing causes problems. Swallowing disorders, or dysphagia, affects 40% of the ones older than 70 due to dementia, trauma or medication side effects, and as a consequence 30-60% of the patients in homes for the elderly are estimated to be malnourished 2 . The swallowing disorders may also cause the food to enter into the airways which causes anything ranging from coughing to pneumonia. It is therefore important to formulate foods and nutritional supplements which have suitable rheological effects for safe swallowing. Previous studies have indicated an effect of fluid elasticity on swallowing 3 . In the present study the effect of elasticity in fluid foods was evaluated by well-define edible model fluids with the aim of determining if fluid elasticity effects the ease of swallowing. MATERIAL AND METHODS Edible model fluid foods were developed having specific rheological characteristics 4 : x Newtonian fluids (constant shear viscosity), x Boger fluids (elastic, constant shear viscosity) x Shear thinning fluids (elastic, shear rate dependent). The model fluids were based on maltodextrin and xanthan 5 with the addition of iodine (Omnipaque ® , GE Healthcare) to make them opaque to x-rays to enable videoflouroscopic analysis during clinical trials. The rheological properties were evaluated using shear rheometry (ARES G2, TA Instruments) and Hyperbolic Contraction Flow 6, 7 . Sensory evaluation by 12 patients suffering from dysphagia together with quantitative videoflouroscopy was performed at the Department of Imaging and Function, Skåne University Hospital, Sweden. The patients were asked to grade the samples through a five digit Effect of shear vs. extensional flow during swallowing Mats Stading 1, 3 , Waqas Qazi 1 , Magda Nyström 1 , Marco Berta 1 , Margareta Bülow 2 and Olle Ekberg 2 1 SP Food and Bioscience, Gothenburg, Sweden 2 Skåne University Hospital, Malmö, Sweden 3 Chalmers University of Technology, Göteborg, Sweden ANNUAL TRANSACTIONS OF THE NORDIC RHEOLOGY SOCIETY, VOL. 23, 2015 63