> It doesn’t hit you at first. It tastes just as plain and feels just as slippery as the other three cartridges. In just a few milliseconds, though, a very sour taste invades your taste buds.

What chemical is causing that? Because I don’t think you can explain that with denatnonium. Or maybe extreme stimulation can cause some kind of intra-gustatory synesthesia in some people. Or it’s a cultural thing, like we had to import the concept of umami from Japanese, where they in turn often use the same word for green and blue.