FOOD FUNDAMENTALS
Smell and taste
Smell and taste
Molecules in food dissolve in saliva and register as tastes when
they come into contact with your tongue. Airborne volatile
molecules released by food are detected by your nose as smells.
Perceiving our meals
Molecules released by food in the air or by
chewing dissolve when they meet moisture,
such as mucus in the nose and saliva in
the mouth. They can then be detected
by specialized nerve cells. These cells
transmit electrical signals to the brain,
which identifies and categorizes each smell
and taste. Our noses can pick up hundreds
of different kinds of smells, but our tongues
primarily detect five tastes—possibly more
(see pp.16–17).
Scent molecule
Mucus-
secreting gland
Olfactory receptor cell
Supporting
cell
Scent molecule
dissolving in
mucus
Scent molecule
binding to
receptor
Food particle
Supporting cell
Taste receptor cell
Sensory nerve
OLFACTORY
RECEPTORS
ORTHONASAL
OLFACTION
How taste works
The tongue’s surface is full of taste
receptor cells. Chemicals from food
and drink dissolved in saliva come
into contact with these cells.
How smell works
Your nasal cavity has a thin layer of mucus.
When scent molecules dissolve into it, they
bind to the ends of olfactory receptor cells.
WHY DOES THE
SMELL OF COOKING
MAKE YOU SALIVATE?
When you smell food, sensory
information is passed to the
brain, which sends nerve signals
to the salivary glands. Saliva is
produced to prepare
for the first stages
of digestion.
CHEWED
FOOD
MUCUS
TONGUE
T
AS
TE
BU
D
SALIVA
S
A
L
I
V
A
US_018-019_Smell_and_Taste.indd 18 18/01/2017 09:41
18
FOOD FUNDAMENTALS
Smell and taste
19
N
E
R
V
E
S
I
G
N
A
L
S
T
O
B
R
A
I
N
Scent molecule
The dry air on a plane makes our
mouths dry and our noses stuffy,
interferring with the moist media in
which molecules from food and drink
dissolve. This means taste and smell
receptors don’t detect molecules
properly. Our sensitivity to sweet and
salty foods drops by 30 percent on
planes, so in-flight meals are often
salted to give them an extra kick. Oddly,
umami tastes seem to be unaffected.
WHY DO MEALS ON PLANES TASTE BLAND?
Why do foods have
tastes and smells?
As the first humans evolved, they made
a wide range of food choices every day.
This means we have evolved more taste
receptors than animals who stick to one
type of food. As infants, we like sweet
tastes and reject bitter ones—this is
thought to stem back to our evolutionary
past where sweet tastes signaled high-
energy foods and bitterness could be a
warning for poison. Our desire for salty
and umami (savory) tastes are thought
to be driven by our need for salt and
other minerals, and for protein.
ONE PAPILLA
ON THE TONGUE CAN
CONTAIN HUNDREDS
OF TASTE BUDS
High calorie
Sweet foods such as
honey provide high
amounts of calories.
Fresh or rotten?
Distinguishing between fresh
(nutritious) or rotten (potentially
dangerous) fruit would have
been helpful for our ancestors.
Vital minerals
A taste for salt exists
because sodium is one of
the macrominerals we
need to survive.
Sign of poison
Typically, bitter tastes signal
poisonous foods, but with
experience we can learn to
like some bitter tastes.
RETRONASAL
OLFACTION
FRESH ROTTEN
To the brain
Olfactory receptor cells in the
nose and taste receptor cells on the
tongue send nerve signals to the
brain to register smells and tastes.
CHEWED
FOOD
Smelling in reverse
Food in the mouth releases scent
molecules that waft up the back
of the throat (retronasal olfaction)
rather than through the nose
(orthonasal olfaction). Most of
what you taste is actually made
up of smells detected via
retronasal olfaction.
N
E
R
V
E
S
I
G
N
A
L
S
T
O
B
R
A
I
N
S
W
E
E
T
S
A
L
T
Y
B
I
T
T
E
R
TONGUE
MUCUS
S
A
L
I
V
A
US_018-019_Smell_and_Taste.indd 19 23/02/2017 11:26
18
FOOD FUNDAMENTALS
Smell and taste
19
N
E
R
V
E
S
I
G
N
A
L
S
T
O
B
R
A
I
N
Scent molecule
The dry air on a plane makes our
mouths dry and our noses stuffy,
interferring with the moist media in
which molecules from food and drink
dissolve. This means taste and smell
receptors don’t detect molecules
properly. Our sensitivity to sweet and
salty foods drops by 30 percent on
planes, so in-flight meals are often
salted to give them an extra kick. Oddly,
umami tastes seem to be unaffected.
WHY DO MEALS ON PLANES TASTE BLAND?
Why do foods have
tastes and smells?
As the first humans evolved, they made
a wide range of food choices every day.
This means we have evolved more taste
receptors than animals who stick to one
type of food. As infants, we like sweet
tastes and reject bitter ones—this is
thought to stem back to our evolutionary
past where sweet tastes signaled high-
energy foods and bitterness could be a
warning for poison. Our desire for salty
and umami (savory) tastes are thought
to be driven by our need for salt and
other minerals, and for protein.
ONE PAPILLA
ON THE TONGUE CAN
CONTAIN HUNDREDS
OF TASTE BUDS
High calorie
Sweet foods such as
honey provide high
amounts of calories.
Fresh or rotten?
Distinguishing between fresh
(nutritious) or rotten (potentially
dangerous) fruit would have
been helpful for our ancestors.
Vital minerals
A taste for salt exists
because sodium is one of
the macrominerals we
need to survive.
Sign of poison
Typically, bitter tastes signal
poisonous foods, but with
experience we can learn to
like some bitter tastes.
RETRONASAL
OLFACTION
FRESH ROTTEN
To the brain
Olfactory receptor cells in the
nose and taste receptor cells on the
tongue send nerve signals to the
brain to register smells and tastes.
CHEWED
FOOD
Smelling in reverse
Food in the mouth releases scent
molecules that waft up the back
of the throat (retronasal olfaction)
rather than through the nose
(orthonasal olfaction). Most of
what you taste is actually made
up of smells detected via
retronasal olfaction.
N
E
R
V
E
S
I
G
N
A
L
S
T
O
B
R
A
I
N
S
W
E
E
T
S
A
L
T
Y
B
I
T
T
E
R
TONGUE
MUCUS
S
A
L
I
V
A
US_018-019_Smell_and_Taste.indd 19 23/02/2017 11:26
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