A supertaster has significantly more of the structures on the
tongue known as
fungiform papillae. These are the structures that house
taste buds. Approximately 25% of all people are supertasters, and being a supertaster is
inherited. Conversely, 25% of people have significantly less tastebuds. These people are known as
nontasters.
Many tastes provide a stronger sensation in supertasters than in normal tasters and a weaker sensation in nontasters. To a supertaster, saccharin is much sweeter, capsaicin (the chemical that causes chili peppers to be spicy) burns more, and there are some bitter-tasting chemicals (the synthetic propylthiouracil amongst them) that normal tasters can barely taste, nontasters cannot detect, and supertasters find horrific. Supertasters rarely drink black coffee or alcohol, and few smoke tobacco.
It is relatively easy to test whether a person is a supertaster. Simply place a drop of blue food coloring on the tip of the subject's tongue. The fungiform papillae will remain pink while the rest of the tongue will turn blue. Now the density of fungiform papillae can be compared with that of known nontasters, supertasters, and normal tasters. The test is so simple, that it is commonly used in elementary school classes as a simple biology experiment.