The taste test strips exhibit a taste due to a dominant allele on chromosome number seven, and the ability to taste these compounds is present in about 70% of the U.S. population. The ability to taste is due to two different sets of alleles. These compounds are present in various naturally occurring foods, and are selected due to their similarity to bitter alkaloids and cardiac glycosides, used by the plant to reduce browsing by herbivores.
Thus, their presence is a result of natural selection both for the plants which produce them and the animal which benefits from the ability to sense them. It is a benefit to be able to detect them and avoid bitter tasting foods, some of which might be harmful if swallowed. Hence, it is a trait selected for in populations evolving in an area which had/has such plants.
Unlike PTC, which taste bitter if an individual can taste it at all, Sodium Benzoate might taste sweet, salty, or bitter. It would generally taste salty to an individual who can taste the bitterness of PTC.