A comparison of the effects of tasting and chewing foods on the flow rate of whole saliva in man

Abstract

The objective was to determine the relative contributions from gustatory and mechanical stimulation of salivary flow in response to consumption of three foods. In a preliminary study on 6 males and 6 females the weights of normal bite-size portions and their chewing times for rhubarb pie, boiled rice, and raw carrot were established for each subject. In the main study the foods were either (a) divided into the calculated bite-size normal portions or (b) the portions were mashed (rhubarb pie), untreated (rice) or finely ground (raw carrot). The subjects chewed the foods of type (a) in the normal way but, with type (b), simply held the food between the palate and the dorsum of the tongue, with no masticatory movements (tasting). After the normal chewing time the food was not swallowed but spat into a weighed container; the volume of saliva secreted was determined from the increase in weight of the food portions. Rhubarb pie elicited a significantly higher flow rate than did the rice and carrot; the flow rates in response to tasting, as a percentage of those in response to chewing were 86.7 ± 12.2, 79.3 ± 17.9 and 73.4 ± 15.4, respectively. It is concluded that in humans the effect of the gustatory stimulation of foods is much more important than the mechanical stimulation from chewing in producing the flow of saliva.