Phenylthiocarbamide, also known as PTC, or phenylthiourea, is a synthetic organic molecule. It has the unusual property of either tasting very bitter, or being virtually tasteless, depending on the genetic makeup of the taster. The ability to taste PTC is a dominant genetic trait. PTC tasting is one of the most frequently administered genetic tests in human populations.

The ability to taste PTC is present in about 70% of the overall human population, varying from 58% for Australoid peoples to 98% for Native American populations. One study has found that non-smokers and those not habituated to coffee or tea have a statistical higher percentage of tasters than the general population. There is conflicting evidence whether a higher percentage of women taste PTC versus men [1].

Reference

L. Kameswaran, S. Gopalakrishnan, M. Sukumar, (1974). Phenylthiocarbamide and Naringin Taste Threshold in South Indian Medical Students, Ind. J. Pharmac., 6 (3). 134-140.