I watched The Magic Schoolbus. I was a huge Miss Frizzle fan. We had the books, and the CD-ROM, and the VHS tapes. My mom would even say, "Seatbelts, everyone!" before we went on a trip. We were so hardcore. That's how I learned the different sense of tastes: sweet, sour, salty, and bitter. (Glucose, hydrochloric acid, sodium chloride, and quinine, eff-tee-arr.)
So when my dad asks me, "Do you know the fifth taste receptor?" I tell him, "Ptth, Dad, there are only four taste receptors. That's how it was at Phoebe's old school." He handed me a Wall Street Journal article. Read and weep.
So I stand corrected! Japanese researchers in 1908 first discovered the separate taste, and isolated it as monosodium glutamate as the chemical responsible. MSG has been a generous seasoning in Asian food since them. The fifth taste is savory, called umami, said "you-mom-ee." Western scientists, until more recently, have been hesitant to call it "the fifth taste" because it doesn't work in the same way as the other four tastes, with specific synapses, instead it uses specialized receptors to secrete a neurotransmitter.
Something like that. I'm not a biologist, I don't really know.
Things like soy sauce, parmesan cheese, and shiitake mushrooms are naturally high in umami, ditto for seafood like anchovies and cod and crustaceans like lobster and shrimp. Carrots and tomatoes are supposedly umami-rich, as is, surprise surprise, seaweed! Truffles, too. I really want to try truffles. Any foods one would usually associate with the term savory have a pretty decent amount of umami in them. This discovery has apparently opened up a whole new host of culinary options -- which is totally exciting when I'm watching Top Chef and Richard starts in on a umami emulsion that I actually know what that is!
It goes to show that the human's sense of taste is far more sophisticated than we often give it credit for. The philosophy of taste meets the science of eating!