A chemical relative of phenylthiocarbamide called PROP

A chemical relative of phenylthiocarbamide called PROP reveals that there is a group of individuals who are extremely sensitive to PROP (tasting extremely bitter), although most individuals do not taste PROP at all.  Those sensitive to PROP are called supertasters and also

Bitter Receptor Gene (TAS2R38), 6-n-Propylthiouracil (PROP) Bitterness and Alcohol Intake

What is PROP sensitivity?

Abstract. Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil (PROP) has been associated with greater acuity for bitter and for some sweet tastes. Thus far, few studies have explored the relationship between PROP taste sensitivity and hedonic responses to bitter and sweet.