Effects of Food Characteristics on Masticatory and Swallowing Functions in Healthy Young Adults

Beyond oral function, the physicochemical properties of food, such as acidity and hardness, significantly influence nutritional intake. Clarifying the relationship between subjective and objective metrics for assessing oral function can help establish simple methods for selecting food with safe and suitable properties tailored to individual oral functions. To objectively and subjectively evaluate the chewing and swallowing processes of gummies with varying hardness and acidity in healthy young adults and to examine relationships between subjective and objective evaluation metrics. Ten healthy young adult men (mean age: 29.8 ± 3.6 years) with no history of oral hypofunction or dysphagia were included. Participants chewed and swallowed four types of gummies (hard with acid, hard without acid, soft with acid, and soft without acid) at their own pace. The subjective evaluation included sensory assessment of chewing and swallowing. Objective evaluations included electromyographic analysis of masticatory and swallowing-related muscles and analysis of the food properties of gummies that were spat out just before swallowing. Correlations between subjective and objective evaluation metrics were assessed using Peason's correlation analysis. The physical properties and acidity of food significantly affected muscle activity and sensory evaluations of masticatory and swallowing functions. Hard gummies, particularly those without acidity, showed significantly greater masseter and temporalis muscle activity, a higher number of chewing cycles, and longer chewing time than soft gummies. In contrast, no significant differences were observed in swallowing-related muscle activity or swallowing duration among the gummy types. Furthermore, strong correlations were observed between subjective evaluations and mastication-related objective parameters, whereas correlations with swallowing-related metrics were limited. Differences in food hardness caused by the presence or absence of acidity affected the masticatory and swallowing functions of healthy young adults. Furthermore, we identified a relationship between subjective and objective evaluations. Our findings provide fundamental data for investigating the effects of food physical properties on sensory evaluation, mastication, and swallowing functions.