The present study examined the ability of physiological parameters of chewing to discriminate between six foods of differing shapes and textural properties. Parameters were measured from masseter electromyograms, which were recorded from healthy and young subjects while they chewed the test foods. Analysis of conventional parameters showed that the number of chewing cycles dropped by 8.8 cycles upon a 100-kPa increase in food fracturability and by 6.6 cycles upon a 5.0-kJ/m3 increase in food adhesiveness. Analysis of the newly developed parameters showed that a 100-kPa increase in food hardness increased the T25, T50 and T75 values by 0.015, 0.020 and 0.021 points, respectively, whereas a 100-kPa increase in the food fracturability decreased the T25 and T50 values by 0.061 and 0.070 points, respectively. The results suggest that combining several physiological parameters will enhance discrimination between foods because individual parameters are sensitive to different food properties.
Together with other measures, analyzing the activity of the masseter, a muscle responsible for closing the jaw, can provide objective information about food texture. The present study used electromyography to examine the quantitative relationships between various physiological parameters associated with masseter activity during chewing and the textural properties of food. The study focused on everyday foods rather than the model foods that are usually tested in laboratory studies. In addition to analyzing the textural properties (such as hardness and adhesiveness) using conventional physiological parameters, we also developed new parameters, TP values, to assess the masseter activity patterns specifically. The combined use of these physiological parameters is expected to aid clinicians and the food industry in their interactions with individuals who, owing to their age and sequelae of cerebrovascular diseases, have particular difficulty verbalizing their experience of chewing foods.