Effect of bitterness on masseter muscular activity and cerebral blood flow during chewing

Abstract

This study aimed to clarify the effects of bitterness on masseter muscular activity and cerebral blood flow during chewing. Twenty healthy dentate adults were asked to chew three types of gummy jelly with different degrees of bitterness （non-bitter gummy jelly, slightly bitter gummy jelly, and bitter gummy jelly） for 20 s, and masseter muscular activity and cerebral blood flow were recorded. The integrated values of masseter muscular activity per cycle were compared among the three types of gummy jelly. Next, the average value of cerebral blood flow was calculated for 10 s each in three sessions: before chewing （at rest）, during chewing （10 s after starting chewing）, and 5 min after the end of chewing. After examining the temporal changes in the cerebral blood flow, the amount of change before and during chewing was calculated and compared among the three types of gummy jelly. As a result, the integrated value of the masseter muscular activity during chewing of the three types of gummy jelly was similar, and no significant difference was observed among the three types of gummy jelly chewing. Cerebral blood flow increased significantly during chewing, decreased after chewing, and tended to recover to the pre-chewing state. Change in cerebral blood flow was lowest when chewing bitter gummy jelly and increased in the order of slightly bitter gummy jelly and non-bitter gummy jelly. Significant differences were observed among the three types of gummy jelly. From these results it was suggested that masseter muscular activity was not affected by bitterness, and that cerebral blood flow was increased by chewing but was affected by the degree of bitterness.