This video is sponsored by Skillshare. Bitter, salty, sour, sweet, umami — is there
nothing more? There may indeed be, according to emerging science. There could be a sixth basic
taste, and a seventh, and an eighth. Our taste buds may be able to perceive certain kinds of
fat, certain kinds of carbs beyond just sugar, certain minerals beyond just salt, and maybe even
water itself. We're going to look at the evidence for all of those. And now, you might be thinking,
"Wait a minute, of course I can taste fat and carbs. Fat and carbs are my favorite
tastes." Well, you've got to remember the difference between taste and flavor.
Flavor is the combined experience that we get via a few distinct sensory systems.
"We smell the food as well as we taste the food. Because those things happen at the same time,
people find it very difficult to separate the two."
This is Dr. Carl Philpott, professor of rhinology and olfactology
at the University Of East Anglia. "People inevitably will feel like
they kind of taste these things ordinarily, and fatty foods or something like cream, I guess,
or something like that, that's got a fat content, and they're going to say, Yeah,
'I can taste that,' but it's probably, a large part of that is obviously the smell of it."
And our smelling system is way more sophisticated than our other taste perception systems. By some
estimates, we can smell over a trillion distinct odors. Most of the detail that we experience in
food and drink is smell. And there's other things too like the hot sensation we get from chili
and the cool sensation we get from mint — that's called chemesthesis, and some people consider that
to be part of flavor. Then there's astringency, which is that dry feeling you get in your mouth
from red wine or from certain unripe fruits. Some people consider that to be part of flavor
too. Personally, I'd lump it in with texture. And taste is certainly part of flavor, but strictly
speaking, taste is only this thing that we experience via these receptors called taste buds
that are in our mouth and at the very top of our throat. Most taste buds are on our tongues. Taste
is pretty much what you sense on your tongue, and it happens when certain substances fit into
those receptor cells like a key into a lock. "In simplistic terms, a receptor has a certain
shape and the thing that comes in, the molecule that you're trying to pick up,
has a certain shape that fits within that. And then when those two things fit together,
that enables what we call a G-coupled protein reaction to occur inside the cell."
It causes a whole biochemical chain of events to unfold that ultimately opens up a pathway to your
brain. When sugar, for example, hits one of your taste buds, it effectively completes the circuit
that lights up the sweetness bulb in your brain. For the existence of a "taste modality," as they
say, to become broadly accepted, scientists like Dr. Philpott want to see basically two things.
They want to see what is the actual physical receptor pathway that the substance is acting on,
and then they want to see whether people are aware of what they get via that pathway.
And they can assess the latter by a couple of methods. They can look at responses inside
people's brains, or they can, you know, like, talk to people. This is how scientists proved
the existence of umami, starting with Japanese chemist Kikunae Ikeda in the early 20th century.
It's an event somewhat infamously dramatized in a corny video made by the company Ikeda went on
to co-found, Ajinomoto, the original producer of MSG. As the story goes,
Ikeda's wife Tei made the family a dashi broth and, while tasting it, he had an epiphany.
He thought, 'This is doing something to my tongue that is totally distinct from sweet,
sour, bitter or salty.' "Tei,
would you run to the grocery for me? For konbu, I want dried konbu!"
"They're not open this late!" "Please, Tei, just go and get what you can."
"This is crazy!" "Please!"
Dude, how about you go to the store? Are your legs broken?
Anyway, scientists later proved that amino acids called glutamates form a
key that can fit into the lock of a few different receptor types in the taste buds.
That's the biochemical pathway proven. They also had to prove that people are actually aware of it,
and that's a little more complicated. Our way of verbalizing what we experience is entirely
determined by our cultural context, right? Not everybody has the literal vocabulary for umami.
"If you went to Japan, for instance, obviously where the term came from, people are very much
familiar with that as a concept. A colleague of mine did a survey of the local population
in Switzerland and asked them just to describe, when given monosodium glutamate, what it was
they were tasting. And there were about 40 different things they came out with, so."
I mean, for example, I know what umami is, but when I put straight MSG on my tongue,
I could swear that it tastes kind of sweet — not just meaty or savory or other words
that people use to describe things like umami, but it tastes sweet to me. Is that my nature
or my nurture? So you've got the cultural complexity on one hand and the biochemical,
neurological complexity on the other. All of this explains why there could be scientific controversy
over such a seemingly simple question like, can we taste fat? But here's the evidence for that one.
Oleogustus, some scientists are calling it, and it's not the taste of fat per se, but rather
free fatty acids. Most of the lipids that we actually eat from oils and animal fats,
these are triglycerides — three fatty acids, those are the long squiggly things,
all stuck to one glycerol, that's the short line on the end there.
Now we definitely perceive triglycerides. We feel them. That is one source of creamy texture in the
mouth. However, both human and animal studies have indicated an ability to taste free fatty
acids — fatty acids that have been broken off from that glycerol. The breakdown of triglycerides into
free fatty acids is something that happens to food as it ages and it spoils. As a result,
people seem to have evolved to find lots of free fatty acid taste and/or smell to be repulsive,
especially certain kinds of fatty acids that result from spoilage. But triglycerides also
break down another way in your mouth. "I mean, obviously saliva in the mouth does
allow for some initial breakdown of molecules through initial digestion. So, we know that that's
where this sort of digestive process starts." Now this is pure speculation on my part, but I
do wonder if this is maybe one of the reasons why chocolate can be so much more delicious
if you just let it melt slowly on your tongue. Particular types of fatty acids that are freed
by the enzymes in your saliva seem to taste good, particularly good to certain people. Or again,
mice. Tons of things that we think we know about people are really things that we know about mice,
because mice are easier to study. Here's a study where scientists found that mice who had more of
these certain kind of taste receptors demonstrated a preference for foods containing oleic acid
and linoleic acid. There's also a human study where they put nose clips on people, and then
they diluted their samples into these viscous liquids to hide the texture of the samples. And
the people were able to tell the difference between samples that contained the linolenic
acid and samples that didn't. One reason why the fatty taste is not yet
broadly accepted may be that not everybody has it. Taste preferences are not just people being fussy.
People are born with different tasting hardware, and at least some people's tasting hardware might
be able to detect starchiness as well. This is a very new area of research spearheaded by Dr. Juyun
Lim at Oregon State University. She and colleagues have done these experiments where they gave people
a compound that blocks their sweetness receptors, and the people were still able to taste carbs.
Carbohydrates are just different arrangements of sugars. Simple carbs taste sweet to us.
One sugar hanging out by itself, or maybe two stuck together. This is sucrose, table sugar.
It's going to taste sweet to us. Really, really big amalgamations of sugars all stuck together,
complex carbs — those do not fit into the lock, the sweetness lock on our tongue.
However, Dr. Lim's research indicates that enzymes in people's saliva break complex carbs down into
smaller carbs that people can taste, even with their sweetness receptors turned off. People
describe it as like a bready taste, or a floury taste, or a rice-like taste. But again, that's
relatively new research, and as yet, no one has identified any specific receptor that would pick
up the starchy taste. In contrast, scientists have identified a specific taste receptor for calcium,
or at least they've spotted it in mice. Maybe we have it too, and maybe that's why chalk has such
a distinct taste. Yuck. Anyway, people seem to be able to taste a few minerals, not just calcium.
"That's less well-defined, really. I mean, a lot of people are aware of metallic tastes. I see a
lot of people complain of metallic tastes as a specific symptom when they come to the clinic.
I guess a lot of people will have the experience of maybe cutting
their finger and sucking their finger and thinking they get a metallic taste, which
could be the iron in the blood. The hemoglobin molecule contains iron at the center."
Now, that's all empirically indisputable, right? The only question is what actually
are we experiencing when we experience the taste of those minerals? Are they tastes in the
traditional, biochemical, taste buds sense? Or is it something else going on, maybe something
electrical, as has been hypothesized. "I think further research is required to
truly determine whether there is actually a metallic taste, or whether it's just a part of the
chemical reaction that's happening in the mouth, that we're experiencing and picking up on."
Whether it's taste or smell, or something electrical, galvanism, there is one place
where we are definitely aware of mineral content, and that is in water. We've all had the experience
of getting weird tastes from the tap as we travel from one place to another where the
geology or the pipe systems introduced different minerals and metals and such into the water,
but you can get those things out via distillation — distilled water — and then you can do tests with
it. Scientists have known for a long time that insects have a taste response to pure water.
And some of them are arguing now that mammals like us might have one as well.
"I think this is based on mouse models, and the fact they appear to potentially have a receptor,
or respond to water as a discrete sensation. And you may think, well, that's pretty weird."
Indeed! Every definition of water that you can find says right up front that it is tasteless. It
may be that the touch and temperature sensations that we get from water are simply way stronger,
and they drown out this relatively subtle taste sensation that we get from pure water as well.
Or maybe it's a situation like umami, where
people, certain groups of people, simply have not developed the skill of articulating
what they are tasting. This is why something like wine tasting is regarded as a skill.
People practice disentangling the distinct sensory elements of the experience,
and then they learn names for those elements so they can communicate what they want.
"I'm going to give you the foundational terminology and really the philosophical
journey around tasting wine, so that you enjoy it more."
That's from a wine buying and tasting course available now on Skillshare,
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tirelessly to help us all better understand what exactly is happening on our tongue.