Although the effect of the quality of dental state on the quality of chewing has been studied extensively, almost nothing is known about the repercussions of emotional states on masticatory muscles activity observed during chewing. The objective of this study was to evaluate the effects of positive and negative emotional states on the electromyographic (EMG) activity during food ingestion. With this aim in view, we employed an association of pictures and sounds taken from the international affective picture system (IAPS) and the international affective digitized sound (IADS) system was used. These effects which varied in valence neutral to pleasant or unpleasant were used to investigate masticator muscle activity in 26 young adults exposed to these stimuli during the mastication of cheese. The emotional state was evaluated by recording variations in cardiac rhythm. There were fewer chewing bursts and less muscle activity during unpleasant stimuli compared to pleasant and neutral stimuli, resulting in a shortened chewing sequence.