to foods when cooking, if one desired. He called the new taste umami,
from the Japanese words for delicious (umai) and taste (mi). Some
folks characterize the umami taste as “savory,” others “meaty,” and
others “mushroomy.” However, for nearly a century not many folks
acknowledged umami as a distinct taste, and certainly in Europe and
America the discussion was confined to the canonical four.
Then in the 1990s, taste scientists in Japan demonstrated the exis-
tence of a fifth type of taste receptor cell and associated taste receptor
proteins. This receptor cell responds to glutamate with taste recep-
tor proteins that are metabotropic (GPCR) glutamate receptors. The
characterization of receptor proteins imparted—at least in the eyes of
some—legitimacy to umami finally being accepted as a fifth taste.
Glutamate is an amino acid—where there is protein, there is
glutamate. And the umami receptors in the tongue are activated not
only by glutamate but also by some of the other amino acids present
in protein. Thus, the umami taste may have developed over the course
of evolution to assist in the detection of protein-containing foods, im-
portant for survival.
Summarizing this way of understanding taste: tastes do not exist in
the world “out there”; what does exist are ions and molecules of var-
ious sizes and shapes. Tastes are mental experiences, existing within
the internal subjective world of our perception; these mental experi-
ences are associated in some way with neural signals that originate
with the taste receptor cells and travel to the brain, where they bloom
into the activation of networks of neurons and glia within particular
regions of the brain. How particular configurations of brain activity
are related to particular mental experiences of the various tastes is an
unanswered question, another instance of the mind-body problem.
The cranial nerve fibers carrying taste sensory information enter