Model foods: a controlled stimuli for mastication

Mastication, a complex process modulated by oral-sensory feedback, is often studied by recording muscle activity and, less frequently, jaw movements. Numerous studies, mainly using natural foods, have attempted to relate this modulation to food texture, in particular hardness, with contradictory results being reported. Objectives: The aims of this work were to: 1) develop edible model foods of defined and controlled rheological behaviours; 2) simultaneously record muscle activity and jaw movement during chewing of two model foods, to determine the effect of differences in food texture on mastication. Methods: Model foods presenting with predominantly either plastic or elastic rheological behaviour were developed. Each model food type consisted of 4 products of different hardness. Fifteen male participants, with normal dentition aged 24.1 ± 1.9 years, were selected. Activities of the masseter and temporal muscles were recorded by surface electromyography. Jaw movements were recorded simultaneously by electromagnetic induction. Participants were instructed to masticate 3 replicates of each plastic and elastic product during two sessions (3 x 4 = 12 samples per session). Results: Food hardness is well described by muscle activity. Jaw movement measurements are required to describe the modulation based on other textural characteristics; vertical and lateral jaw movements are strongly affected by food type. Masticatory frequency is initially dependent on food hardness but overall is more strongly dependent on food type. Conclusions: Model foods are valuable materials to use for studying mastication as they provide controlled and reproducible stimuli to monitor modulation of mastication. This allows the relative effects of different food textures to be quantified. Simultaneous measurement of muscle activities and jaw movements allows greater understanding of masticatory function, illustrating the high level of modulation achieved by the central nervous system. Acknowledgements: This work was supported by French government funding.