Sensory User's Manual
using chemistry, physiology, physics and psychology to develop a wine
Wine tasting can be an occasional
pleasant diversion or a time-and-resource-consuming passion. It can
be conducted casually or formally. No matter what level of orientation
or dedication is involved, some basic background knowledge and a logical
approach can greatly increase individual enjoyment. Most American
wine drinkers cheat themselves by not knowing how to taste; many talk
the talk but fail to walk the walk, so a lot of ordinary-tasting wines
gets sold at extraordinary prices.
Wine tasting is actually a
complex proposition involving much more than simply sipping some fermented
grape juice. There are many variable factors that affect an individual's
perception of flavor in wine. There are chemical, physical, mechanical,
physiological, and psychological variables.
The type and quality of the wine itself
is only one aspect of tasting. Others are the size and shape of the
wine glass... the individual's impartial physiological ability to smell and taste, as well as his individual flavor preferences...
the temperature of not only the beverage itself, but also the ambient
temperature and humidity of the tasting site... mental condition, how hungry, tired,
and attentive the taster is can also affect relative judgment, as
well as any preconceived notions and other psychological factors.
The FOUR ELEMENTS of FLAVOR
To understand these variables, let's first look at the phenomenon
of taste from a physiological standpoint. Flavor, although it may
have slightly differing meanings, depending upon who is using the
term, always refers to food. A food chemist may use "flavor"
only to refer to aroma, while a chef is likely to include taste, texture,
temperature, appearance, and arrangement in his context. The International
Organization for Standardization (ISO)
defines flavor as:
Complex combination of the olfactory,
gustatory and trigeminal sensations perceived during tasting. The
flavour may be influenced by tactile, thermal, painful and/or chemesthetic
While the senses of smell and taste
are significant, flavor is not an experience limited
to these, but a combination of experiences from the senses of smell,
taste, touch, and, less obviously, sight. Each of these personal perceptions can be notably affected and altered by context and ambient conditons.
ONE - SMELL: Acute, Ancient and
The nose can sometimes even beat the eyes in the race for setting
up tasting expectations. An aroma can carry beyond the line of sight, from one room to another
for example. Of the five senses, smell is the most acute,
approximately 1,000 times more sensitive than the sense of taste.
As a result, what is termed flavor is influenced by roughly
75% smell (olfaction) and 25% taste (gustation) in healthy individuals.
Ever notice how foods seem to taste bland or less distinctive when
the nose is blocked by a common cold?
and taste are the chemical senses because their receptors
are stimulated by chemical molecules, rather than by energy from light,
pressure, or sound. As little as one molecule in a million may be
detected by the nose, but it takes a minimum of one part per thousand
to stimulate the tongue. As sensitive and accurate as this organ is,
relatively few people ever realize its potential for sensory enjoyment
by learning both how it funtions and the language terms used to describe smells. Professional
food and wine tasters and perfumers use analogies to common experience
to record or classify aromas. Experts are those that practice and use their
sense of smell most frequently.
For a substance to be smelled, it
must have a certain degree of volatility (evaporate easily)
and some of the molecules it contains must be hydrophobic (able to dissolve in oil, but
not water). Odor molecules are typically larger than those that stimulate
The odor vapor must contact receptors
which cover the organs of smell, a pair of olfactory membranes located
deep in each uppermost nasal cavity. These membranes are brownish-yellow, roughly
the size of a postage stamp, about two centimeters thick and covered
in a thin layer of mucous. There
are 200 distinct kinds of nasal receptors. They function using 50
million olfactory neurons, each with cilia that extend into and through
the mucous. On the cilia are the receptors that capture the scent
molecules, signaling the neurons to send the scent message to the
brain for sensation, reaction, and interpretation.
The sense of smell is ancient and
primal, one of the earliest senses evolved, for locating food, warning
of danger, and regulating sexual behavior. Unique among the senses,
the scent message passes directly through the limbic system, the emotional
center of the brain, on its way to conscious identification in the
cortex. Reaction to certain smells may be instinctive; identification of those smells requires a certain amount of experience and training.
Fatigue and Adaptation
While smell is the most easily stimulated of the human senses, it
is also the most fragile. Most of us have experienced detecting the
aroma of cooking, maybe even from outside the house. In pursuit, we
trace it to the kitchen where it becomes stronger. After standing
there for a few minutes, however, the cooking odors may no longer
be noticeable. This fatigue of the sense of smell is part of sensory
adaptation: the self-adjustment to a constant level of stimulus in
an environment, so that the individual retains sensitivity to changes.
This adaptation also occurs for the sense of sight in a darkened theater
or hearing in a noisy city.
Some adaptation is short-term; recovery
and return to the degree of sensitivity prior to exposure may only
take a few minutes. Research has also demonstrated that constant environmental
odor exposure can cause adaptation that lasts for days or weeks, even
after removal of the odor source.
is a great variation between individuals in the elements to which
they are sensitive. A person's absolute threshold is the smallest
amount of stimulus required to produce a sensation. Once that threshold
is reached, the individual typically only recognizes a particular smell as either "familiar" or "new", unless they have been trained to identify it. Scientists
have proven that the nose can detect and distinguish between thousands
of different smells, depending upon individual aptitude and training.
Even individuals lacking the ability
to smell specific odors (1anosmia)
can often be induced to learn them by repeated exposure. Very little
research has been conducted to either explain or rectify serious sensory
problems of smell or taste, which can arise from congenital defect,
illness, or injury, and may effect one of every 150 human beings2.
To date, scientists have cataloged over 17,000 different smells. About
10,000 can be distinguished by humans, although no one knows precisely
how this ability works. In the early 1900s, a researcher named Henning
suggested there are really only six categories of smells, combinations
of which account for all the detectable odors and aromas.
Henning arrayed these categories into
a three-dimensional prismatic map whereon, his theory suggests, all
smells could be plotted to some point on one of the surfaces. For
example, it should be possible for something to smell fruity, putrid,
resinous, and burned, but impossible to have a smell that is putrid,
spicy, and resinous. The combinations are interesting to plot
make-up of wine includes many trace elements that contribute to the
combination of smells. Some of these same elements are also found,
frequently in higher concentrations, in other familiar foods, spices,
flowers, etc. Consequently, wine smells may often bring to mind these
other familiar things, albeit with more subtlety and much less obvious
or instantaneous recognition. With training, concentration, and practice,
nearly anyone can learn to dissect and describe these elements of
TWO - TASTE:
Categorization and Individual Sensitivity
While there may be a vast array of aroma categories, generally only
four tastes have historically been considered: bitter, salty, sour,
and sweet. There really is no precise definition of "basic taste";
these four only differentiate and describe common taste sensations.
has historically been one of the least understood sensory mechanisms.
We know it is sensed by nerve receptors
called buds and that there are about 9,000 of them on the average
Misinterpretations of research conducted in the late 1800s, led to
"tongue maps" that suggested that the basic tastes are sensed primarily
by specific areas, such as the tip or center.
Although taste buds were noted to be of different sizes and shapes, depending upon their location, subsequent investigation
proved that all of them contain the same kinds of taste receptor cells (papillae) that supply the sensations of taste. The entire top surface of the tongue can sense
all of the various tastes.
Combinations of basic tastes, along with the accompanying various
aromas, account for different flavors. Taste compounds are generally smaller
molecules than those of odors and, unlike odors, must be water-soluble (hydrophilic) to cause sensation.
Sensitivity to specific tastes varies
considerably with individuals. It is possible in fact to be taste-blind.
The test uses a chemical called phenylthiocarbamide, which
tastes extremely bitter to some persons and quite bland to others.
Some research has suggested that there is higher alcoholism incidence
among the genetically taste-blind.
Another physiological variable is the rate and volume of salivation. Saliva dilutes liquids and can surpress the volatility of aromatic compounds and can also change or disguise textural elements3. Hesitant sipping of wine can accentuate these effects.
Additional theories of taste perception come into Western consciousness
from Eastern thought. Asians generally add "hot" (the capiscum or capsaicin taste of chili peppers; see chemesthesis below) to the four basic tastes. At
the beginning of the 1900s, Japanese scientist Kikunae Ikeda identified
this sensation as more complex and variable than merely hot. He isolated
one element that causes this taste in meat, milk, mushrooms, and seaweed
broth as the amino acid glutamate and called the sensation
Rather than a specific taste, umami
is best described as a distinctive quality or completeness of flavor.
The nearest English equivalent would be "savory" or "delicious." Oriental
food often gets umami, its "complete" flavor, by the addition of monosodium
The scientific journal Nature published an article in the Spring of 2002, reporting that American scientists
Charles Zuker and Nick Ryber identified a taste receptor for
amino acids, supporting the idea of Umami. Wine typically contains
from one to four grams of amino acids per liter. While still controversial,
there are ongoing studies of umami and it is an emerging consideration
in food and wine circles.
THREE - FEELING:
Texture, Body, Tannin, Alcohol and Temperature
The sense of touch figures in the overall flavor impression by conveying
temperature, texture and pressure, the feeling differences
that exist between cold iced tea and hot coffee, between plain fruit
punch and carbonated soda, between filtered and unfiltered apple juice,
between smooth pudding and crunchy cookies, or between the burn of
jalapeño or the cool of menthol. These sensations of touch,
irritation, or thermal differences are called chemesthesis and may be experienced in the eyes, mouth, nose, or throat. Much of
the touch information of flavor is conveyed to the brain through the trigeminal nerve.
The body of a wine is felt
as light or heavy, thin or full, rich or crisp. Body
is one of the most often misunderstood components of wine. The description
"full bodied" is frequently applied to wines that are high in either
alcohol or tannin or in both, without the actual texture and weight
of the wine being "full" at all. Body should be thought of as the
relative "thickness" or viscosity of the wine.
One of the most prominent elements
of wine "flavor" is tannin, more a sensation of touch rather
than taste. It is also a significant flavor component of tea, chocolate,
soy, pecans, walnuts, and the skins and seeds of many fruits, other
than grapes, such as blueberries, dates, kiwi, peaches, persimmons,
pomegranates, raspberries and figs.
Tannin leaves a puckery, astringent
feeling on the tongue, gums, and cheeks and can sometimes also taste
bitter. Wine tannins come primarily from grape skins and oak barrels
Red Wine on the "Winemaking"
page) and vary in strength and character. In the mouth, tannins can
feel fine, round, and smooth or gritty, coarse, and angular. Tannins
are one of the few flavor elements in wine that cannot be smelled.
|Wine served cold gives a taste impression
that is less sweet and more acid and astringent than the same wine
at a warmer temperature. This is one reason to serve fruity wines
chilled, while dry, astringent ones are best near or just below "room"
Alcohol also is mainly experienced
as an irritation of the touch sense. When the proportion is too high
for the other flavor elements, alcohol may give a "burning" sensation
in the nose as well as a "hot" feeling in the back of the throat or
the roof of the mouth.
The phenomenons of fatigue and adaptation
discussed earlier regarding smell are also considerations with taste.
Astringency and bitterness require up to ninety seconds recovery in
order not to influence the flavor of the next wine. This can be a
very long time between tastes. A good swallow of water or bite of
bread helps. Sugar also takes a while to fade from the tongue. Chocolate,
which combines astringency, bitterness and sweetness, has an extremely
long aftertaste, can foul the palate for wine evaluation, and is not
recommended within three hours prior to serious tasting. Cheese also
clouds the ability to judge wine; as wise old French wine merchants
say, "Achetez avec l'eau, vendez avec le fromage" (Buy with water,
sell with cheese.)
FOUR - SEEING: Clues Only; Don't
This idea of sight affecting flavor is not hard to grasp if one thinks
of some food which looks unappetizing, but then tastes very good.
The reverse is also true. How often is an item selected from a cafeteria
line that appears very tasty but turns out to be bland or worse?
This expectation based on appearance often psychologically sets
up our taste buds. In wine, this sight prejudice leads us to expect
that transparent and bright wines will be good-tasting, and wines
that are cloudy or dull in color will not. Although this does not
necessarily hold, still our sense of sight sets us up psychologically
for gustatory enjoyment or disappointment. Because humans rely upon vision more than their sense of smell, rightly or wrongly, appearance has a strong influence on odor perception4.
Color can be an indicator of what
the nose and the mouth might expect. Clues as to the grape varietal
identity and the age of wine can be revealed by its hue and transparency
or opacity. White varietal wines may appear from very pale greenish
and brightly clear (suspect youth and bone dryness) to deep golden
brownish and approaching translucence (probably well-aged, possibly
nectar-like). Red varietals run from brickish red and nearly transparent
(may be older, mellow) to deep opaque bluish-purple (expect young,
brash, tannic). Bright pink rosé or blush wines are often youthful,
while orangey-bricky ones are usually past their point of prime drinkability.
Although they may appear to be in
a range of either red-purples or green-yellows, wine grapes are referred
to as black (noir ) or white (blanc ), depending on
the color of their skins at ripeness. Ripe Pinot Noir, Grenache, and Mourvedre skins range generally in tones of red to reddish-brown and wines made from these varieties
tend towards a garnet or brickish tone. Syrah, Cabernet Sauvignon,
Cabernet Franc and Barbera are more bluish-black when ripe and can make wines so inky-purple they could
refill fountain pens. The hues of the black grapes are consistent
but they become nearly transparent when made into rosé or blush-style
wines. Sauvignon Blanc and Chenin Blanc tend to be green. Semillon
and Viognier are generally more yellow. Gewürztraminer and Pinot
Gris (Grigio ) can have a light tannish-grey cast if allowed
to fully ripen before made into wine. Most unnamed varietals fall
in between these color ranges.
Sight may set up initial expectations
in the other senses, or serve as confirmation after smelling,
tasting, and feeling a wine's properties. When the wine being sampled, for example, shows aromas of tomatoes,
bouquet of earth, flavor of
dried cherries with a velvet-textured mouth feel and light tannins, all of which lead to suspicions of Pinot Noir, a light edge that seems more red than purple
may confirm it.
Putting it all together
Evaluating the physiological factors and chemical properties helps
devise methodology to get the most from tasting wine. The taster can
control serving parameters to intensify the experience and consider
and maintain an awareness of elements which are beyond control but
nonetheless affect the tasting occasion.
to make sure enough vapor is present to get a strong sense of the
wine's smell, use a glass shape that can concentrate the molecules,
filled only one-third full or less to allow space for the vapors to
Tilting the glass over an opaque white surface and observing
the liquid's edge is the best way to judge hue and clarity (although my personal recommendation is to save observation and visual judgment until smell and taste are fulfilled).
swirl the wine to launch some of those molecules into the air and to
increase the size of the liquid surface area from which the molecules
Research has incdicated that taking several short, quick sniffs may help reveal multiple aroma elements. A big, deep sniff of
wine reaches the deep-seated nasal receptors and should cross the threshold
of sensitivity in even the least responsive taster. That first impression of a wine is really important.
Close the eyes and concentrate to form an initial judgment before
fatigue and adaptation set in.
Put enough wine, one-half to a full
ounce, in the mouth and slosh it around to make sure as large an area
of the tongue as possible has a chance to judge the wine's elements.
A lesser amount of wine may not be enough to overcome salivary dilution. Feel the viscosity and tannins.
Allow the wine to settle in the lower
jaw, letting it warm slightly while pursing the lips to breathe in
a small amount of air. Continue sucking in air, making a slurping
sound as the wine and air mix. This volatilizes the wine and sends
it to the back of the nasal cavity, intensifying the smell and flavor
experience. After swallowing, notice which flavors and feelings are
left and how well they linger.
There are times swallowing is not recommended, especially when learning about wine or making decisions about wine purchasing. The physical (anesthetic) and psychological (confusion) effects of alcohol are insidious. the only way to postpone them is by spitting, which is totally acceptable and respected by industry professionals. The importance of this precaution far outweighs any social inhibitions. It can also mean the difference between an activity that is considered social (wine tasting) or one that is anti-social (binge drinking).
Notice the word used is "postpone", rather than "avoid"; some amount of alcohol is absorbed into the bloodstream even before swallowing, while the wine is in the mouth. Only so many wines can be sampled and spit before even the most experienced and professionally dignified taster will cross over the legal limit of sobriety. Evaluating several wines on the same
occasion, therefore, calls for discipline.
Organization of the tasting procedure is also needed when sampling multiple wines. Different contexts
call for different methods.
One technique is to sample and evaluate
each wine completely and separately, before moving to the next one.
For some people, this gives them a complete and memorable picture
of the individual wine. A large informal "cocktail party" tasting event, where
one glass is carried from table to table and used to sample many wines,
dictates this manner of tasting.
A different plan may be used
at formal "sit-down" wine tastings with "flights" of two or more wines, each in a separate glass. In
this situation, it's possible to smell and evaluate the aromas of all of the samples
before tasting any of them. Proceed through once, smelling each in
order, then return to those that left the weakest or least distinctive impression for a
second chance to coax more from them.
Classify the wines, based on
aromas, from "weak" to "strong" to "defective" to set the order of
actual tasting. It requires discipline to delay tasting the strongest or
most appealing wine, but it provides a chance to form a more definite
impression of the lightest-smelling wines, without being overwhelmed
by the "bigger" wines. Wines that have suspected defects, such as
hydrogen sulfide (rotten egg), or TCA (corkiness), are postponed until last, to avoid "polluting" the senses.
Communication and Memory
specific smells and flavors of wine is not important to the average
consumer; most decide that a wine simply tastes good or not. Critics
and judges, however, need to learn and apply standards of terminology.
Consumers can enhance their tasting experience by learning these terms
in order to communicate better with their fellow tasters, their wine
merchant, and, perhaps most importantly, to develop a memory of their
likes and dislikes.
Dr. Ann Noble taught sensory evaluation of wine and developed the Aroma Wheel from more than 20 years of research and practice at U.C. Davis. Her Aroma
Wheel website explains how to get one of these tools and use it train your "nose
and brain to connect and quickly link terms with odors...using materials
available from the grocery store."
Many of the smells and flavors in
wine are described in terms of other fruits. Gas chromatography enables
separation and identification of elements in a compound, according
to the constituent's volatility. This technique has enabled chemists
to establish that there are, in fact, several odoriferous molecules
that are shared by wine along with apples, pears, currants, raspberries,
oranges, or bananas. These include acetic and butyric acids, the alcohols
propanol, terpinol and hexanol, the carbonyls ethanol, acetone and
diacetyl, and the esters isoamyl acetate, ethyl caproate, and ethyl
butyrate. Different combinations and amounts of these and other compounds
give fruits their distinct aromas and flavors and provide great variety
A wine palate is part ability and part experience. The individual's preferences for and sensitivity to smell and taste elements,
along with the memory of their taste history, combine to form
the palate. In developing this personal wine palate, remember to consider
the temperature, the texture, and the feel, as
well as the flavors.
Besides judging the wine, learn to recognize
which flavor elements help you arrive at that judgment and use accepted
terms to describe them. Use the swirl, sniff, and slurp method
to enhance your tasting ability. When you find yourself absentmindedly
swirling, sniffing, and slurping your water glass, coffee cup, or soda
can, you have reached the first level of expertise and commitment
to appreciating fine wine.
1. The Anosmia Foundation posts articles and links to information for those with the inability to perceive smells. RETURN
2. The University
of Connecticut established their Smell
and Taste Center in 1981, one of only half a dozen such institutions
in the United States. Their web site contains a wealth of information. RETURN
3. The Journal of Food Research published research in 2015 by a team at the University of Naples that reveals even more significance in gustation to the salivary variable than had previously been credited. RETURN
4. The Color of Odors, by Gil Morot, Frédé́ric Brochet and Denis Dubourdieu, 2001. RETURN
Although some information is repeated, there is more focus on identifying wine flavors in our Describing Wine article in the Cosumerism section.
Delwiche, of the Ohio State University Sensory Science Group, maintains a web site with accurate and up to date
explanations on the science of smell, taste, and flavor in very easy-to-understand
terms, with many accompanying diagrams.
Lauriann Greene, President of French
Wine Explorers, wrote Intro
to Wine Tasting, a simply
terrific and sensible article describing techniques and methods of
wine tasting, what to look for and what to expect.
There are many tools available to help
train your sense of smell. Look in the Self Help box on our Information
Links / Educators and Classes page.
The Monell Chemical Senses Center in
Philadelphia site has several articles of related interest, such as Sensation
Chemist Alexander Pandell's The
Acidity of Wine is an excellent discussion of the acidic elements which dominate wine
chemistry and how total acids and pH affect flavors.
Cornell University has
several pages on the biochemical and dietary, among other properties,
There is a Society
for Research on Umami Taste whose web site is devoted to the latest developments of this phenomenon (note "English" button under menu at top left).
Kalin Cellars' umami
page has further
thoughts and links concerning this element of taste.