Little information is available on human chewing in the natural environment. Former work provided evidence of an individual consistent chewing pace across different days (J Dent Res 90(10):1206-1210, 2011). However, the influence of food toughness and texture on chewing function was not investigated. Physical properties of food modulate chewing contractions through sensory feedback. The aim of this study was therefore to investigate human chewing activity according to different food types in field recordings.
Method:
Electromyographic activity was acquired unilaterally from the masseter in 22 participants (11 f & 11 m, 20-30 y) in the natural environment during four different meals at one week intervals, by means of portable recorders. Three different types of food (carrots, bread rolls and standardized pizza) were eaten in randomized order. Time-frequency properties of chewing activity were assessed with previously validated algorithms. Repeated measurements ANOVA at alpha = 0.05 was used for statistical analysis.
Result:
Overall, for carrots, the mean number of chewing cycles per sequence before swallowing was 27.0, the 5th and 95th percentiles being 15.2 and 41.5, respectively; corresponding values for bread rolls were 16.9, 7.1 and 28.1; for pizza 18.5, 11.2 and 28.1. Overall, chewing activity occurred on average at 1.77 Hz (SE 0.05 Hz) for carrots, at 1.60 Hz (SE 0.05 Hz) for bread rolls and 1.67 Hz (SE 0.05 Hz) for standardized pizza. Chewing frequency as well as number of cycles differed significantly between carrots on one side and the other two food types (p<0.001 and p=0.001 respectively). Individual chewing paces for each food type were stable across all chewing sequences and all meals (95% CI for the difference = -0.02-0.03 Hz).
Conclusion:
Our findings provide evidence of a modulation of chewing pace due to different food types in the natural environment, stable over a longer time interval.