This study examined the influences of rheological properties on mastication in eight healthy male subjects by recording an electromyogram (EMG) of the masseter (MS) muscle during chewing. Four different agars were tested: 0.5 and 1.5% ordinary agars (0.5OA and 1.5OA), and 2.5 and 4.0% . The hardness, adhesiveness and cohesiveness differed among the four agars, which is most likely because of the differences in the concentrations and constituents of the agars. Mastication time and the average amplitude of the MS EMG during chewing were longest and largest, respectively, with the 1.5OA followed by the 4.0IA. The activity pattern of the MS EMG differed between the first and last cycles of chewing sequences in each of the agars used; there were no differences between the first cycle activity patterns or the last cycle activity patterns when comparisons were made between the four agars. These results suggest that the rheological properties of the agars modify mastication and that the activity patterns of the MS muscle change during chewing. PRACTICAL APPLICATIONSThe present findings obtained by the analyses of rheological properties and physiological parameters, especially by the "T P " technique, suggest the following possible uses: (1) the T P technique can analyze foods at different angles from analysis by rheological properties; (2) a combination of rheologi-1

We previously developed the TP technique to discriminate between the activity patterns of skeletal muscles. In this study we aim to identify the TP value(s) that can be used to sensitively evaluate the activity patterns of the suprahyoid (SH) muscles during swallowing. We also analyse the effect of food textural properties on the activity patterns of the SH muscle during oral and pharyngeal swallowing. Three test foods consisting of 3%, 6% and 9% of a thickening agent, Mousse-up (MU) were prepared. Their textural properties differed significantly. Swallowing of 9% MU involved a significantly longer average duration than 3% MU. The average T50 value for 6% MU was significantly larger than that for 3% MU. However, the average T20 and T80 values of the test foods did not differ. Thus, the T50 value is particularly suitable for evaluating SH muscle swallowing patterns. Moreover, test foods that vary in their textural properties elicit different durations and patterns of SH muscle activity.

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/m 3 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. PRACTICAL APPLICATIONSTogether 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. bs_bs_banner A journal to advance the fundamental understanding of food texture and sensory perception Journal of Texture Studies

The present study examined sequential changes in masseter activity patterns observed during chewing of four different agar samples in eight healthy young males. Two parameters, T(50) and D(50), were specifically used for evaluation of the activity patterns of individual bursts. Statistical significances were detected in regression coefficients (21.9% of 32 trials) and Spearman's rank correlation coefficients (28.1%) between the calculated T(50) values and chewing cycles, whereas no significant differences among the four agar samples were found. Three (I-III) types of activity patterns of masseter bursts during chewing sequences were classified by the D(50) values, which were derived from the T(50) values. The three types physiologically corresponded to incrementing (Type I), decrementing (Type III) and mixed discharge patterns (Type II). The classification of activity patterns suggested the usefulness of D(50) values in the sequential analysis of masseter activity patterns.

Times for recognition of fruity flavors in six gummy candies were measured using an electromyography-based system in 23 young healthy participants. They were instructed to chew one of the gummy candies at a random order and to press a button as soon as possible when they recognized what flavor was. The measured 181 recognition times showed two distributions, normally ( n = 107) and non-normally ( n = 74). The overall average of the normal distribution was 7.5 seconds (±2.34 seconds; standard deviation), and there were no differences in the average ratios among the gummy candies. Eighteen of the participants reported 41 inconsistent reports with flavors that were provided by the manufacturer. The most frequently observed report was an apple-flavored gummy candy (14, 34.1%) mainly for a pear-flavored. However, there was no significant correlation between the numbers of recognition times and those of inconsistent flavors among the used gummy candies.

Masseter activity patterns during chewing, which were quantitatively assessed using T50 values, were compared between the right and left sides of healthy young males. Surface electromyograms were recorded from both masseters, and each participant was asked to chew four different agar samples at his own pace across two separate sessions. The four agar samples, each possessing differing textural properties, consisted of two normal and two distinctive agar varieties. The Pearson's correlation coefficient was calculated for each pair of T50 values to evaluate the degree of synchronization of activity patterns between both masseters. A three-way analysis of variance revealed significant main effects of the 'participant' and 'experimental session' factors, but not of the 'test food'. The number of significant coefficients increased stepwise by increasing the number of chews per sequence. These results suggest the importance of the initial stages of chewing sequences in facilitating the synchronization of bilateral masseter activity patterns.

Flavor recognition times were measured in 23 young, healthy participants of both sexes using an electromyography-based system. The participants were instructed to chew a gummy candy, which was randomly selected among six commercially available types, and to press a button immediately on flavor recognition. A total of 107 normally distributed, flavor recognition times were analyzed, with an average time of 7.5 seconds (± 2.34 seconds, standard deviation). No significant differences were found among the six types of candies in terms of recognition time. Analysis of the association between flavor recognition and chewing phase showed that 70 (65%) of the analyzed 107 recognition signals occurred between 0.2 seconds before and 0.4 seconds after the end of jaw closing. Recognition signals occurring during the jaw-opening phase prolonged its duration by an average of 21%, whereas those occurring during the jaw-closing phase did not influence it.

Few studies have evaluated the effects of activity patterns of the jaw closing muscles assessed by specific parameters on jaw opening in subsequent cycles during the chewing of food. The objective of this study was to quantitatively analyze the effect of the masseter (jaw closer) activity patterns on suprahyoid (jaw opener) activity during subsequent cycles. The assessments were performed while participants naturally chewed six test foods that differed in size dimensions and textural properties. Surface electromyograms of the masseter (on the habitual working side) and suprahyoid muscles were recorded in ten healthy young adults, each of whom randomly received one of the six test foods. The activity patterns were assessed using three parameters specifically developed for their quantification. Changes in suprahyoid activity during each of the subsequent chewing cycles were examined by three amplitudinal (minimum, maximum, and net values of the integrated suprahyoid electromyogram) parameters and one durational (active duration) parameter. The main finding was that two of the three activity pattern parameters had a statistically significant effect only on the three amplitudinal parameters in three of the six test foods. These results suggest that masseter activity patterns partially affect suprahyoid activity during subsequent chewing cycles and that the effect is food dependent. A possible neural mechanism responsible for this effect is presented.