How Does Taste Work?

Your sense of taste isn't just a chemical catalog of what's in a food or drink -- it's a complex physiological and psychological process. Learn what we know (and don't know!) about taste in today's episode of BrainStuff, based on this article: https://health.howstuffworks.com/mental-health/human-nature/perception/taste.htm

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio, Hey brain Stuff,
Lauren Vogelbam here. We learn about taste in grade school,
and out of the five senses, it seems like one
of the most simple. There are no cones, rods, or lenses.
There are no timponic membranes or minuscule bones. Yet scientists

(00:25):
know less about taste than they know about sight and hearing.
So why is taste so mysterious? To start with? Taste
is wrapped up in the greater issue of flavor. A
taste is a chemical sense perceived by the specialized nerve
receptors that make up our taste buds. Our perception of
flavor is a fusion of multiple senses, not just taste,

(00:48):
but also smell, touch, and temperature. In addition to taste buds,
we have nerve cells throughout our oral and nasal cavities
that detect molecules that give us a sense of heat, wellness,
or dryness. For example, you know foods or drinks that
are spicy, hot, minty, or puckery. It gets even more

(01:08):
complicated because our interpretation of sensory data is always subjective,
and flavors are perhaps more subjective than most Some people
have inherited genetic traits that make certain foods that others
find pleasant taste disgusting, like cilantro. Others have higher or
lower concentrations of taste receptors than most of us, and

(01:30):
as we all know, food tastes different to different people,
we don't all enjoy the same flavors. Over the past
couple decades, science has expanded its definition of taste. We
now understand that we have at least five primary tastes sour, bitter, sweet, salty,
and savory, with at least four more hypothesized. Science has

(01:53):
also challenged the tongue map, that biology class staple that
charts distinct regions of taste and is almost certainly bunk food.
Scientists have even tampered with taste receptor cells, blocking or
stimulating them in an effort to cut sugar and salt
out of foods without sacrificing flavor. Today, let's talk about

(02:13):
the physiology and psychology of taste and flavor. Taste begins
with electrical impulses. Sure of food or drink is usually
involved too, But as we've talked about before on the
show Sensations, you know our bodily responses to stimuli like pressure, light,
or chemical composition only become perceptions like touch, vision, or

(02:38):
taste when they reach the brain. In our mouths and noses,
certain chemical stimuli activate the chemo receptors responsible for our
perceptions of taste and smell. Because both our reactions to
the chemical makeup of an object. The two senses are
closely related, though the chemo receptors involved with each tend
to pick up on slightly different ranges of molecules. That's why,

(03:02):
if you've ever been gunked up with a cold, the
subtlety of food was probably muted. You weren't getting the
full picture. In humans, the chema receptors that detect taste
are called gustatory receptor cells. About fifty of these receptor cells,
plus some basal and supporting cells, make up a single

(03:23):
taste bud. The average adult has around ten thousand taste buds,
and not just on your tongue. Some are spread elsewhere
throughout your oral cavity. On your tongue, many of your
taste buds are contained in what's called papilli. These are
the small bumps that dot the tongue. There are three
different types, arranging from smaller mushroom shaped bumps on the

(03:45):
front of the tongue with only a few taste buds each,
two larger, deep, goblet shaped bumps at the back of
the tongue with hundreds of taste buds each. The papilli
help you taste food and drink because they greatly increase
the surface area of your tongue and therefore the number
of taste buds that can fit on it. And they
can help create friction between the tongue and food at

(04:06):
breaking the food up. And they can help saliva wash
over food and actually get particles of it to our
taste buds. Each taste bud is a little bundle set
into the surface of the tongue or the base of
a papilla. A taste bud looks a little bit like
a flower bud. Each of the petals that make it
up is a gustatory receptor cell. These cells have spindily

(04:31):
protrusions coming up to the tip of the taste bud
called gustatory hairs. These taste hairs can brush up against
bits of food that you eat with the help of
your saliva. Proteins on the surface of the hairs will
bind with particular types of molecules and stimulate the sensation
of taste. The receptor cells are connected to nerve fibers

(04:53):
that pass on electrical impulses to the gustatory area of
the cerebral cortex. The brain then interprets the sensations as taste,
together with other sensations like smell and maybe heat. If
you just ate a chili pepper, your brain gives you
a concept of flavor. There are a lot of compounds

(05:14):
in foods and drinks that give them their nuanced flavors.
For strawberries, researchers have isolated over three hundred compounds that
affect our experience of smell and taste. For tomatoes, it's
over four hundred. Until recently, scientists accepted four basic categories
of tastes, sweet, salty, sour, and bitter. These categories are

(05:39):
the building blocks of flavor and at the root of
other tastes. Each primary taste triggers a particular taste receptor.
The receptors can and do respond to multiple tastes. The
four basic tastes went unchallenged for years. However, in the
early nineteen hundreds, a Japanese chemist by the name of

(05:59):
Kikune Keda set out to identify the compound in a
common soup broth called kombu dashi that made it taste good.
He was looking to find something that could be produced
cheaply and easily that could add flavor to nutritious foods
and thus entice people to eat better. He was also
looking to make money, and wouldn't we all be lucky

(06:21):
to make money doing something good for the world. In
nineteen oh eight, he landed on the molecule glutamic acid
as the key stuff in kambu or seek help that
makes dashi so sippable. It's an amino acid, a building
block of protein that we understand today occurs in lots
of meats, cheeses, and vegetables, from steaks to parmesan to

(06:43):
tomatoes and Kida. Further proposed that our detection of it
is a fifth basic taste, a one that humans developed
an affinity for because it occurs in these nutritious foods.
In English would call this taste savory. But when Haita
came up with a product that carries this taste, a
salt format of glutamic acid called monosodium glutamate or MSG,

(07:07):
he called the taste umami in his marketing materials, ubami
being a colloquial term for tasty. Yes, the word umami
is just an early nineteen hundred's marketing term. Kaida's research
didn't really hit the Western world until the MSG company
that he started began trying to expand outside of Asia

(07:28):
in the nineteen eighties. By the way, MSG is fine
for the vast majority of people to consume unless you're
on a low salt diet. In general, if you feel
a little weird after eating a dish that it's heavy in,
you're probably just dehydrated that always drink water anyway. Researchers
have since found the taste receptors responsible for sensing amino

(07:50):
acids like glutamic acid, thus solidifying savory as a fifth taste.
Now that the gate is open, however, other contend have
entered the field. French researchers have identified a potential gustatory
receptor for fat, so fatty might be a sixth taste.
Other researchers have suggested that our basic tastes could further

(08:12):
include metallic, watery and alkaline, the opposite of acidic. And
just as scientists are re examining the basic tastes. They're
also redefining the tongue map. The classic tongue map divided
the tongue into regions of sensation bitter in the back,
sour on the sides, salty on the front edge, and

(08:33):
sweet at the tip. This concept also goes back to
the early nineteen hundreds. A lot of work was being
done in nutritional science at the time, but since then
a research has determined that although the tongue does have
varying degrees of sensitivity, some areas can perceive certain tastes
better than others. There was no real truth to the

(08:54):
strict tongue map. Furthermore, although taste receptors often react strongly
to a single taste, most do respond to multiple taste stimulations.
The primary tastes gave early humans clues about what food
was good to eat and what was potentially harmful. Sweet
foods had energy loaded carbohydrates. Salty foods had important vitamins

(09:19):
and minerals. Savory foods had protein. Sour foods could be
healthy like apples, or spoiled like rotten milk. Bitter things
could be poisonous. And actually one bit of the tongue
map was more accurate than the rest. The back of
the tongue is particularly sensitive to better flavors. The raining

(09:40):
hypothesis goes that this was useful and last ditch detection
of toxic substances before we swallowed them. These days, the
processed foods we eat are often painstakingly flavored by professional
flavor chemists, so the tastes that we experience when we
eat them are sometimes signifying nutritional value, but it isn't

(10:00):
actually there, but we still crave and respond to our
ancestral favorites. Of course, a person's taste is a lot
more complicated than that. Physically, we perceive other flavors beyond
the five ish primary tastes. Spicy foods can feel hot
due to two different categories of compounds that both trigger

(10:23):
the same nerve receptors in your mouth and knows that
sense actual heat. They're chemically tricking your mouth into thinking
that it's slightly on fire. Chili peppers and the capsaisin
in them affect one type of nerve receptor. A plant
in the mustard family, including masabi and other pungent things
like cloves, garlic, cinnamon, and ginger, will activate a second

(10:46):
type of heat receptor. This is also the receptor that
registers the slight nasal burn of carbonation and sodas. Black
pepper hits both of those Sesshuan peppercorn or any of
the numbing hot dishes it's made with that activates both,
plus yet another type of receptor, the same one that
your body uses to sense what's basically tickles extremely light touches,

(11:11):
like when a bug lands on you. It produces the
same feeling as the pins and needles you get when
a limb falls asleep, or when you hit your elbow
just wrong, or feel a vibration, and so yes, tickle
is a flavor. Evolutionarily, these plants probably developed these compounds
to be unpleasant to mammals like us, and therefore to

(11:35):
prevent us from eating that plant's fruit and thus crushing
up its seeds before they have a chance to sprout
and grow. But suckers, some of us humans decided that
we enjoy those flavors or bitter tasting things like black
coffee or artichokes. That's part of why, despite having figured
out a lot about our taste buds and other flavor

(11:57):
chema receptors, we still don't have a very good idea
of how any given person's overall sense of taste works.
Your brain doesn't just catalog the molecular makeup of a peanut,
butter and jelly sandwich. It processes the smooth and soft
and maybe crunchy textures and the cravable combination of salty,

(12:17):
savory and sweet sensations, and maybe throws in a little
nostalgia for a time that someone you love made a
similar sandwich for you. The same sandwich eaten on two
different days might even taste different, just based on your mood,
like sometimes when you're upset, eating anything feels gross, and

(12:38):
research has shown that hunger really can affect flavor. In
a study from back in two thousand and four, groups
of students who had not eaten in sixteen hours could
perceive weaker sucrose and salt solutions than those who had
eaten only an hour before. In order to perceive a taste,
the students who had just eaten needed a sucros concentration

(13:01):
fifty percent higher, and assault concentration doubled that of those
who had not eaten. But apparently our poison detecting sense
never rests. An empty stomach or full stomach had no
effect on the perception of bitterness, speaking of it's time
for me to go get a refill on my coffee,
which I take with just a little bit of oatmelk.

(13:23):
It's a matter of taste. Today's episode is based on
the article how taste works on how stuffworks dot com,
written by Sarah Dowdy. Brain Stuff is production of iHeartRadio
in partnership with how stuffworks dot Com and is produced
by Tyler Klain. Four more podcasts for my heart Radio,
visit the iHeartRadio app, Apple Podcasts, or wherever you listen

(13:46):
to your favorite shows.