CHAPTER TWO

SENSORY PERCEPTION

The most important aspect of foods and beverages are probably their nutritional value because we must eat to survive. There is no biological necessity for alcoholic beverages however. They are consumed for pleasure, for psychological reasons, not physiological ones. Hence, the sensory attributes are of paramount importance. As with foods, we take pleasure from a combination of our visual, olfactory, taste, and tactile perceptions. There are, in most cases, established standards for how alcoholic beverages ought to look, smell, taste, and feel and we will describe them.

Beverages are evaluated using the senses of sight, smell, taste, and the tactile or sense of touch. It is also believed that thermal perception, the awareness of hot and cold, is important in the sensory evaluation of both foods and beverages. It may even be possible that the perception of pain is used in wine evaluation since highly acid or tannic wines may actually be triggering pain receptors in the mouth. In evaluating beverages, the taster first looks at, then smells, and finally tastes and feels them.

The abilities of various tasters to identify the many visual, olfactory, taste, and tactile components will vary widely based on their sensory equipment and on their experience. Of the two, experience is the more important. Although people differ in their visual, olfactory, and taste capabilities, with most persons the differences are not significant. What an inexperienced taster lacks is a frame of reference. They may see, smell, and taste the same things as an expert, but these perceptions have no meaning.

Consider this corollary: if a person from another culture, who had never seen or tasted broccoli, were to eat some, it would not have the same sensory meaning as it would to someone who was familiar with the vegetable. Both tasters would be able to see the green color, it would smell and taste the same to both, and they would both have the same aftertaste in their mouths. To the inexperienced taster however, the appearance, smell, and taste would be new; they would be able to relate it to little or nothing with which they were familiar. The other taster would have a great deal of information stored in his or her memory which would enable them to make a rational evaluation. The broccoli either is the right color or it is not. The shape and texture is either proper or it is not. The smell and taste are as they ought to be or they are not.

This is why some very experienced and expert people can taste a malt scotch whisky and identify the specific distillery it was produced at; perhaps even the year it was distilled and the approximate number of years it had been aged in wood. This is not as mysterious as it may appear. This person has probably tasted this particular whisky many times and it's sensory characteristics are implanted in the memory. Just as many people could correctly identify strawberry and raspberry ice cream, the expert can differentiate between whiskies, vodkas, gins, beers and so forth.

Therefore, to learn about alcoholic beverages, one must evaluate, and evaluate carefully, as many as possible in order to build a library of information in the memory. It is true of course that some are better suited for this than are others, just as some people can be trained to service an auto better than others, or to run faster, or jump higher. Barring any physical disability though, and providing there is interest and commitment, anyone can be trained to know something about auto repair, to run faster, to jump higher, and to be more skilled in sensory evaluation.

Visual Examination

There is a great deal of information available to the eye but the most important are probably color and clarity. When speaking of color, tasters often use the terms hue, tint, and shade and these are very useful terms.

Color comes from a variety of sources. With beers, it is due to the degree with which the grains, primarily barley malt, are roasted. With spirits it comes primarily from wood although some spirits allow color adjustment with caramel (burnt or cooked sugar). Color in cordials and liqueurs almost always is added. For example, clear or white creme de menthe is the normal color; green creme de menthe has color added to it.

The other main criteria of the visual examination is the clarity of the product. Terms such as brilliant, clear, cloudy, dull, hazy and others are used to describe the clarity. A wine described as brilliant would not only be clear, but it would have a sparkle to it. Dull would be the opposite of brilliant, while hazy indicates some sort of suspended materials can be seen. Most of the beverages we will discuss are filtered to produce a clear and bright product. There are some, such as the cordial Goldschlager, that have added materials (in this case, gold flakes) that are supposed to float around. There are also some beers, wheat beers are an example, which are cloudy and this is normal. With most however, a lack of clarity is a sign of poor processing or storage, or both.

Tasters often manipulate the glasses in specific ways to aid in the evaluation. The glass is tilted to observe how the color changes from the center to the shallow edges. This is an especially useful technique in wine evaluation and can be used with spirits and beers as well.

Olfactory Examination

There is probably more information to be obtained from smelling the beverage than from any other single act, including tasting it. There are only four tastes, sweet, sour, salt, and bitter and no one can be trained to perceive more than these. There are many more odors than tastes, thousands of them, and trained persons can detect 1,000 or more. People can also detect very small differences in concentration since the odor receptors are several thousand times as sensitive as are the taste receptors. The sense of smell is therefore much more advanced than is the sense of taste. A typical wine has some 300 compounds, of which about 200 are more or less odorous and it has only two, sometimes three, tastes. Experienced tasters therefore pay a great deal of attention to olfactory evaluation.

The organs used in odor evaluation are:

Nose: Volatile components (principally esters and aldehydes) rise as vapor through the nostrils and from behind the soft palate, into the upper part of the nasal cavity.

Nasal Cavity: Moisture in the cavity dissolves the vapors and fine nerves (vacilli) carry them to the Olfactory Bulb.

Olfactory Bulb: Located in the brain.

Temporal Lobe: Located behind the Olfactory Bulb. This is the storehouse for memory. Here, sensations of smell awake memories. The experience is analyzed in the Parietal Lobe and judgment is made in the Frontal Lobe.

There are a vast array of odors that can be perceived with alcoholic beverages. The odor standards will be described as we discuss the various spirits, cordials, and beers. We will also point out those odors that ought not to be there such as skunky in beer, excessive woodiness in whiskies and so forth. Flaws, defects, or spoilage can be detected with the nose more easily than with any of the other senses.

Tasters often swirl the beverage in the glass prior to smelling it. The swirling has the effect of mixing the liquid with oxygen and it brightens or "awakens" the odors. Try pouring a wine or whisky into two glasses. Swirl one of them and immediately smell both. Usually, you will detect a noticeable difference between the two and the one that smells the most "alive" will be the one that had been swirled. Obviously, this cannot be done with all glasses. For this reason, it is common for whisky tasters to use small glasses with stems and bowls so that they can swirl them. Whisky distillers and blenders frequently never taste the products. They make their decisions based on the smell and appearance of the spirits.

The sense of smell suffers from adaptation to a greater degree than, for example, does the sense of taste. This means that although odors can be more easily detected, there is a temporary loss of the ability to perceive. For this reason, when the wine is smelled, a long deep sniff is taken, and then the taster pulls away. There is no sense in sniffing for a long period of time. This is in contrast to the actual tasting where the wine is left in the mouth and moved about for an extended period.

Taste Evaluation

Many persons use the terms taste and flavor interchangeably but they refer to two different kinds of perceptions. Taste should be used only with reference to sweet, sour, salt, and bitter while flavor is the combination of tastes and odors perceived in the mouth. When food is chewed, or wine swirled about in the mouth, odors are released which rise up the nasal passages and go to the odor receptors in the brain just as if they had been drawn in through the nose. When people claim that they cannot taste anything due to a cold, they are technically incorrect for the basic tastes can still be perceived. The difference is that they cannot smell anything, either in the mouth or through the nose, and the food/beverage has little or no flavor. The sense of smell is thus an important part of the sensory evaluation in the mouth.

Although the taste receptors (taste buds) are located all over the mouth, specific tastes tend to be concentrated in certain areas. Sugar and other sweet tastes are detected on the front of the tongue, salt on the sides of the tongue, towards the front, sour or acid also on the sides but further back, and bitter at the base (rear) of the tongue.

The terms threshold, adaptation, and reaction time are of importance in sensory perception. Threshold refers to the concentration or strength of a stimulus which must be present in order to be perceived. There is an absolute threshold, that concentration at which a stimulus can be detected but not identified. The recognition threshold is that at which identification can be made. For example; if sugar is present at below the absolute threshold level, it will not be perceived (tasted). If it is present at the absolute threshold level, the person will be aware of a taste, but will not know what it is. When the concentration is raised to the recognition level, the perception will be identified as sugar or sweetness. The recognition threshold for sugar is about one-half of one percent or 0.5% for most people. This is the highest of the taste thresholds, and sour, salt, and bitter tastes can be perceived at lower concentrations. When taste stimuli are mixed, the thresholds will change. This is of great importance in the case of sweet and sour tastes as we shall see.

Adaptation, the temporary loss of the ability to perceive, has been explained with reference to the sense of smell. With taste, it is less of a problem since taste deals with compounds of much higher molecular concentrations.

Reaction time, or sensory lag, refers to the length of time it takes for the stimulus to produce a reaction. Salt has the fastest, and sugar the shortest reaction time, followed by sour and then bitter. The beverage is therefore swirled in the mouth for several seconds, to allow time for taste perception, and sugar or sweetness is the initial one.

The interrelationship of the basic tastes are very important. With wine, for example, the relationship between sugar and acid (sweet and sour) is critical. Too much sugar and the wine is said to be cloying. Too much acid and it is tart or even sour. The perception, however, of sweetness and sourness depends on their ratios. With a totally dry wine (no perception of sweetness), about 1/2 of one percent acid would strike most people as balanced. One percent acid would be perceived by most people as tart or sour. If, however, the wine had more sugar, perhaps one to three percent, an acid level of one percent would probably not be objectionable. In fact, if it did not have more acid, it would not taste balanced. The term in this case (insufficient acid) is flat. With beer, we look primarily for the attributes of hops (bitterness) and malt (sweetness and toasty flavors). Some cordials have so many ingredients that it becomes impossible to identify the individual ones and the taste perception is that of a very complex mix of flavors. Examples are Bénédictine and Chartreuse. Other cordials emphasize a single flavor; the best examples are the orange liqueurs such as Triple Sec and Orange Curaçao.

Just as the glasses are swirled for aeration of the beverage, experienced drinkers will whistle it in during tasting. This consists of holding the liquid in a cupped tongue and inhaling noisily. The effect is the same as swirling a glass - the beverage is exposed to additional oxygen and the aroma/bouquet opens up and becomes more distinct.

Once it is swallowed, or spit out as experienced tasters will do when examining spirits, and often beers and cordials also, the aftertaste is evaluated. Some beverages have a tendency to disappear once swallowed, while others will linger on and on.

Tactile Evaluation

It is important to distinguish between the often confusing perceptions of taste sensations and tactile sensations. Tannins offer particular difficulties. Tannins provide astringency and are felt, not tasted. Inexperienced tasters often mistake the acid taste with the astringent feel of tannins. For example; lemon juice provides acid and is tasted, while strong tea or aspirin produce a rough feel, especially when the tongue is rubbed against the roof of the mouth.

Body or viscosity is another tactile sensation. Alcoholic beverages are more viscous than water because they are an alcohol/water mixture, and the higher the alcohol level, the greater the perception of body. One of the objections to the low alcohol light wines and beers is that they have a watery feel relative to wines and beers of normal alcoholic content.



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