Electromyographic responses to prescribed mastication.

The aim was to understand between-volunteer differences in Electromyography (EMG) behaviour during chewing. EMG was used to record the electrical activity of the temporal and masseter muscles of volunteers, who carried out mastication movements by operating calibrated springs held between their incisors. The volunteers coordinated their jaw movements with the signal produced by a metronome, at four rates: 30, 60, 90 and 120 beats per minute (bpm). Raw data were analyzed to examine the distributions of the intervals between chews. For the highest prescribed chew rates, the volunteers' distributions were very similar. The distributions varied most for the 30 bpm data, suggesting that volunteers differed in their ability to carry out and maintain this prescribed chewing pattern. The data were Fourier transformed to give power spectra in the frequency domain. The low frequency (<10 Hz) region contained spectral features related to the prescribed chew rate. Principal component analysis of the power spectra revealed that readings from each volunteer clustered together, and the clusters could be largely separated. Such grouping was found irrespective of whether data from each chew rate were analyzed separately or simultaneously. This indicated that within-volunteer variance, arising from the different chew rates as well as between-session variance, is lower than between-volunteer variance; even when individuals are asked to make jaw movements in the same prescribed manner, they can nevertheless be uniquely distinguished by their muscle activity as recorded by EMG.

Measurement of surface area, gel weight and saliva weight in a gelatin-based gel over the course of mastication.

The aim was to devise a method for the measurement of total surface area and weight, as well as saliva weight, for a gelatin-based confectionery gel over the course of human mastication for input into separate modelling of flavour release. The method is based on an alcohol rinse to remove saliva, followed by immersion in amaranth dye to give a thin surface dye layer coating the gel fragments. Total surface area is then found by measurement of quantity of absorbed dye. The resulting time profiles for the six panellists showed that surface area reached a maximum of 3000 mm2 with the 4.28 g gel weight being consumed over 41 to 64 sec with differing numbers of swallows (4-6) and chews (52-103). Calculated total relative saliva weights, 498-993 g kg-1, and flow rates, 2.8-5.6 g min-1, were towards the upper range of those reported in the literature.