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Sensory User's Manual
... using chemistry, physiology, physics and psychology to develop a wine palate...

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.

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 effects.

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 Fragile
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 (chemesthesis, discussed later, can also provide strong flavor perceptions). Ever notice how foods seem to taste bland or less distinctive when the nose is blocked by a common cold?

Although not considered an organ of "far sense" like the ears or eyes, the nose can sometimes even outreach both. An aroma can carry beyond the line of sight, from one room to another for example, or emanating from a remote but downwind source.

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 awareness in the cortex, without pausing in the thalamus for identification, as all other human senses do.

Nasal cavity cutaway diagram.Smell 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 taste.

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.

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.

There 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 (anosmia{1}) 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 beings{2}.

Henning's Smell Prism (illustration).Aroma Theory
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 and contemplate.

The chemical 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 complexity.

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.

"Tongue-maps" are wrong.Taste 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 tongue.

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 elements{3}. Hesitant sipping of wine can accentuate these effects.

Eastern Influence
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 "umami."

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 glutamate (MSG).

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. Tannins are also significant flavor components 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.

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" temperature.
Tannins 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 (see
Red, 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.

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 be Fooled
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. Certain observed colors lead to certain expected aromas and flavors. Because humans rely upon vision more than their sense of smell, rightly or wrongly, appearance has a strong influence on odor perception{4}. White wines are expected to smell and taste of citrus red wines are expected to smell and taste of berries; when sensory experience produces an opposite result, doubt is directed at the chemical senses.

Color can be an indicator of what the nose and the mouth might expect, but the visual component of wine appreciation is subject to as many complexities, variables, and subtleties as are the nasal and oral elements. Translation: not all wines made from the same grape in the same region of the same vintage and having the same bottle age, etc., will appear identical in color.

For the wine consumer, hue and transparency or opacity are more reliably indicative of wine age than of varietal content. 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. The hues of the black grapes tend to be consistent with the red wines they make. Colors can become nearly transparent when these are made into rosé or blush-style wines. For white grapes, the relationship of grape variety color to wine color is a great deal more subtle.

Ripe Pinot Noir, Grenache, and Mourvedre skins generally range 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.

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.

METHODOLOGY: 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.

First, 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 be contained.

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).

Next, 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 can escape.

Research has indicated 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.

TERMINOLOGY for Communication and Memory
Human ability to detect and differentiate between odors is excellent, but identifying specific scents is extemely difficult for most. Although they do slightly better describing tastes, naming specific smells and flavors of wine is not important to the average consumer. They generally 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. Bombastic critics cause amateur tasters' expectations of their own abilities to be way too high. Even the most experienced taster can only accurately identify three or four compounds within any given wine.

Ann Noble's Aroma Wheel.

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 in wine.

SUMMARY: Cheers!
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.

Jim LaMar

Although some information is repeated, there is more focus on identifying wine flavors in our Describing Wine article in the Consumerism section.

Dr. Jeannine Delwiche, of the Ohio State University Sensory Science Group, maintains a web site with accurate and very easy-to-understand definitions of sensory terms and an equally friendly FAQ section.

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 and Perception.

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, of Tannins.

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.

Science & Wine is the BLOG of Assistant Professor Paula Silva of the Institute of Biomedical Sciences at the University of Porto, where she agglomerates articles, research papers, and other science communications, as well as posting calendars of conferences, seminars, and workshops related to scientific studies of 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 by a team at the University of Naples in 2015 Investigating the Influence of Saliva on Retronasal Aroma in Red and White Wines and also by a team from the University of Porto in 2014 demonstrating the variability of the Human Saliva Protein Profile at various times of the day. RETURN

4. The Color of Odors, by Gil Morot, Frédé́ric Brochet and Denis Dubourdieu, 2001. RETURN





Page created February 24, 2001; updated September 16, 2018
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