American experts have studied the relationship between the evaluation of the intensity of tastes and the way the products possessing these tastes were degustated. Despite the fact that the concept of the tongue map is now considered obsolete, being consistently and repeatedly debunked in controlled studies, evidence for regional differences in taste intensity has been noted by multiple research groups. And, accordingly, taste perception depends on the method of tasting. The researchers have hypothesized that if the sample is swallowed, the bitter taste and taste of umami is felt stronger than when it is spit out.
To test this hypothesis, two experiments were performed. In the first experiment, participants tasted and evaluated pure flavors (sweet, bitter and umami), in the second they tasted and evaluated specific products (grapefruit juice, salty vegetable stock, savory vegetable stock, iced coffee, and sweetened green tea). It turned out that when all the tasted samples were swallowed, the bitterness indeed was often felt more intensely than with spitting out. Often, but not always. Therefore, the researchers concluded that, the intensity of the perception of taste does depend on the method of tasting. And the tasters should be explicitly instructed to reduce the influence of this dependence on the result of the tasting.