The major role of mastication consists in transforming food into a bolus to be swallowed. This is done through the mechanical reduction of the food into small particles. This reduction is associated with the lubrication of the food fragments by saliva and by the fluids liberated by the degrading food. The resulting bolus is a cohesive and viscous mixture whose elements stick together, but not to the oral mucosa. Thus the bolus can gently glide against the pharynx walls during the swallowing process while preventing particles from going through the trachea. The formation of the bolus during mastication implies the occurrence of various processes that are not only mechanical, but also chemical and enzymatic.

By definition the masticating function only takes place when the ingested food is solid. When the food is half-solid there is no need for mechanical destructuring strictly speaking, but it undergoes a deforming process due to the movements of the oral cavity soft structures (tongue against palate especially), and in that case the food stays very shortly in the mouth.