Tip of the Tongue: Humans May Taste at Least 6
Flavors
Taste is fascinating, complex, and it turns out, very
misunderstood. I love that the sense of taste was highlighted
recently on both Science
Live and picked up by
Fox News online, but found myself editing the generalizations
and inaccuracies in my head as I read on, who knew I was such a
stereotypical scientist?
Here's the deal, and why I'm so jazzed up, taste is not flavor;
this is a big misconception and one that is perpetuated in the
recent taste articles. Many things contribute to FLAVOR (i.e. the
sensory perception as you eat), smell, mouth-feel among others, and
of course taste. But don't fall victim to confusing taste with
flavor. We may say something "tastes" good, but what we really mean
is that we like all the sensations that come together to make
flavor. So no, texture and smell do not affect how we taste food,
they affect how we perceive food as a whole.
We all know about the 5 tastes: salt, sour, umami, sweet and
bitter. But what about the chance that there are more? I agree with
Micheal Tordoff, a behavioral geneticist at the Monell Chemical
Senses Center in Philadelphia, when he is quoted in the article,
relaying his opinion that "There is no accepted definition of a
basic taste. The rules are changing as we speak." In fact there was
a great session that Dr. Tordoff led at the 2011 annual taste and
smell meeting (Association for Chemoreception Sciences) called
"Basic Tastes- Why Five?" This innovative session gave the podium
to scientists pushing the limits on defining new tastes, and
reiterated the rules we currently have in order to determine what
is really a "taste" and what is not. While it's true that there is
no 100% accepted definition, there are some basic guidelines that
are pretty widely held concerning if a "taste" is really a
"taste":
1. The is a evolutionary benefit to recognizing the taste (makes
sense that we have it)
2. There is a defined stimuli that causes a person to identify
the taste (there is a tired and true food/chemical that causes the
taste)
3. There is a specialized transduction mechanism for the taste
(how the tongue gets the info to the brain is unique to the
taste)
4. The signal must originate and be conveyed by the taste system
(i.e. the tongue and associated cranial nerves)
5. The taste must be perceptible and unique (you must actually
taste it and it must be unique)
6. The taste must evoke a response (tasting causes a reaction…
i.e. Yum! or Blech!)
That said, I agree with the fact that fat, calcium and maybe
metal all may one day be considered true tastes. However, where I
think there is a lot of debate surrounds the potential "tastes"
that are really sensitivities by the trigeminal nerve, i.e. this
cranial nerve has free nerve endings that are like live wires on
your tongue and are the ones that help you detect texture (anything
with mouth-feel), temperature (hot cold, mint etc.) and pain
(capsaicin in hot pepper).
These are not the sense of taste, they are the sense of
touch and are sent to the brain by the trigeminal nerve. There is
so interesting new opinions on these sensations, but not a whole
lot of scientific evidence that points at a new "taste".
Taste is a part of the flavor experience, but taste is only
one part and it is very distinct in how it works and what it helps
our brains to understand about the world around us.
Final word, even if receptors exist on the
tongue for a new "taste", if we are not conscious of the reaction,
is it a true taste?
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