The Modern Four Taste Orthodoxy

The idea that there are four basic tastes—sour, salty, bitter, and sweet—was widely taken to be gospel truth until 2002, when the taste receptors for glutamate were identified. Glutamate, and the "umami" flavor it imparts to foods like seaweed, bacon, parmesan cheese, and Doritos, was first identified and isolated by a Japanese chemist named Kikunae Ikeda in 1908. But the four-taste model was so dominant that umami's status as a distinct taste was considered "controversial" until its molecular basis was confirmed almost a century later. Here's the description of umami in a book titled Sensory Processes published in 2002 (before the taste receptors were identified):

Umami originated from a glutamate derived from seaweed. The chemical substance is commonly known as MSG, monosodium glutamate, and, by itself, has no odor and an unusual taste that is approximated, so they say, by appropriate combinations of the four primary taste qualities. Whether umami is a result of the unique combination of the four tastes or an independent classification of is own is open to debate (176).

Oh, they and the things they say.

Umami's been gaining traction—Kikkkoman's current advertising campaign is "discover umami"(.com)—but it hasn't quite arrived. This past Sunday on Iron Chef America, one of the judges said he detected some "umami" in a coconut-based soup, and then he had to define it for the other judges (and perhaps the audience?). His first stab was to call it an "illusory" taste, although he did follow that up by ranking it with "sweet, salty and sour," so perhaps he actually meant something more like "ineffable." Either way it shows how dominant the classical four tastes still are.

Except "classical" isn't quite right word, because it turns out the idea that we only experience four distinct tastes is actually a pretty recent invention—more recent than Ikeda's "discovery" of umami, actually. Traditional Chinese medicine named five tastes: sour, bitter, sweet, pungent, and salty, each one corresponding with one of the five elements or movements that are omnipresent in early Chinese thought. Aristotle claimed there were only two, which doesn't come as that much of a surprise given his characteristic love of dualities. Just as he divided visual perception into the "fundamental colors" black and white, which contain all the elements of all the other colors we perceive, Aristotle thought the whole range of gustatory sensations derived from the "fundamental tastes" of sweetness and bitterness. He also proposed a second-order classification of seven "primary flavors" that corresponded with his rainbow of seven "primary colors": sweet (which included fatty or oily), bitter, salty, harsh, pungent, astringent, and acidic or sour. Hard to say now what exactly the difference was between harsh, pungent, and astringent—I suppose the latter might be something like the tannins in tea and red wine while "pungent" instantly evokes blue cheese although it often just acts as a modifier rather than a descriptor—a pungent smell is strong, not necessarily strongly any particular thing. It's hard to even think of those things as taste categories on the same level as "sweet" or "sour."

But one question that raises is whether or not it's hard to think of them that way because there's some objective difference between sweetness and astringency or because it's just unfamiliar to think of "astringent" as a primary taste category. Certainly tannins cause a particular reaction on people's tongues—is that less of a distinct taste experience than the reaction caused by sugars?

Colors are a useful parallel, again. A linguistics professor I had at NYU told us about this experiment that my casual googling is not coming up with, but here's the gist: if you give children a set of colored tiles and tell them sort them into as many piles as they want, by color, there are predictable, reliable differences between the number of piles they make that correspond to the number of primary colors in their primary language. So, for example, English-speaking kids generally put all hues of blue in one pile while Russian-speaking kids usually separate lighter blues from darker blues because they have two "primary color" words for those shades. It's one of the classic examples of how language can shape how we perceive the world rather than just reflecting it. Also a reason why translation is always imperfect. 

Getting back to the four taste orthodoxy, that was something a German psychologist named Hans Henning  came up with in 1916. He devised a ""taste tetrahedron" with each of the four tastes he thought were primary at the four vertexes. The idea was that flavors could be conceptually mapped onto geometric plane based on which of the primary flavors they were comprised of—a flavor relying on two of the primary tastes would be located on the edge between those two vertexes. Flavors that used three would be on the surface between the relevant three points. And the tetrahedron was hollow, according to Henning, because no substance could produce all four taste sensations. So while taste itself was three-dimensional, tastes were two-dimensional at best. Read more