Effect of Hyposalivation on Fish Cake Mastication in Healthy Individuals.

During mastication, solid food is mixed with saliva to form a bolus. However, little is known about the effects of hyposalivation on mastication. The effects of hyposalivation on masticatory behavior were investigated using fish paste products. Healthy volunteers (n = 21) were instructed to eat two fish paste products (fish cakes and rolled omelets) in a natural manner. These foods are elastic with high water content. Electromyographic activity was recorded in the masseter, suprahyoid, and infrahyoid muscles during mastication before and after atropine administration, which reduced salivary flow. Masticatory dynamics, including electromyographic activity and masticatory cycle time, were compared between volunteers with and without hyposalivation, and among the early, middle, and late masticatory stages. Next, the volunteers (n = 19) were instructed to ingest the food in the same manner and then spit it out at the end of mastication. After atropine administration, spitting was repeated, and bolus properties, such as hardness, water content, and piece size, were compared between the conditions. Hyposalivation did not affect any fish cake sensory evaluation properties; however, masticatory duration for rolled omelet increased considerably. Furthermore, no significant differences were observed between volunteers with and without hyposalivation in terms of masticatory cycle time, muscle activity per cycle at each stage, bolus physical properties, and bolus water content. Owing to the high water content of fish paste products, such as fish cake or rolled omelet, hyposalivation may not substantially affect mastication of these products.