Evaluating, or judging, a wine is a fundamental part of "wine lore". Everyone does it, and at its simplest level the question asked is "Do I like this?" and then, "Why?" At more experienced levels, tasters try to specify what they like - is it the color, the aroma, the flavor? At competitive levels, tasters will assign points to these and other categories, and rank wines in comparison to one another. That's how medals and other prizes are awarded.
A wine glass should be held by the stem or the base. If held by the bowl of the glass, fingerprints may hamper the ability to judge the clarity of the wine. The hand also tends to warm the wine, which in the case of a chilled wine is undesirable.
Evaluating a wine involves four of your five senses. To make it easy to remember, we have simplified wine tasting or "sensory evaluation" to what we call the five "S's" of tasting. First, you "see" the wine. Put the glass against a white background or up to a bright light and make notes as to both its color and clarity.
In a white wine, the color should range from pale yellow to golden. Note that any tinge of brown in a table wine (not a fortified wine like sherry) may be an indication of too much contact with oxygen or "oxidation" - a serious wine flaw. Different types of white wines are expected to have certain shades of color. Young, light wines should be pale straw in color. Older, richer wines will have more gold, while dessert wines might be very amber.
Evaluating a Wine Color in reds can range widely and certain shades are expected for specific types of wines, too. Young, light reds will have light colors with "pink" edges. Heavier reds made from Cabernet Sauvignon (for example) will be purple-black. An older red wine might develop a slight orange hue (not brown).
Clarity of a white wine is easy to judge - just look through the glass. You shouldn't be able to see any suspended material making the wine appear "cloudy". Red wines are harder to judge, particularly the very dark ones, because you can't see through them. The color should be brilliant, not dull. Look at the edge of the wine, just where it touches the glass.
Next, you "swirl" the wine in the glass. This helps to vaporize the volatile aromatic components of wine so that you may smell them more readily. This is why you should only fill a glass a third to half full. Any more, and you will risk "sloshing" the wine out of the glass.
As soon as you "swirl" the wine, put your nose into the bowl of the glass and "smell" the wine, the third "S" of sensory evaluation. You must sniff deeply. During normal breathing, only 5 to 10 percent of inhaled air will get into the upper nasal passage where you do your smelling. So to get more air into this passage, you must really sniff. (What do you do if someone says "Do you smell something burning?" Same technique applies here.) Most of the enjoyment from a wine comes from the smell, humans can recognize over 4000 smells, but only 4 taste. One of the most easily recognized aromas of wine is that of the ripe fruit from which the wine was made. (Chablis and Southern White, made from Carlos, are good examples.) However, many grapes, and the wine made from them, have little distinctive aroma. These can often be described simply as "vinous", meaning they smell like wine but not a particular type.
Often, we apply other commonly recognized names to the smells we pick up in wine: "It smells like apples"; "It smells like cinnamon". The bottom line is that the aroma should be pleasant. Wines that smell like rubber, or cooked vegetables, or old socks, are flawed.
Now, you may take a "sip". Usually, a taster will sip enough wine so that it can be rolled around in the mouth. It's also common to see experienced tasters suck in a small amount of air while holding the wine in their mouth. This "slurping" is done to release more of the flavor.
There are three taste characteristics we normally can identify in wine: sweet, sour (or acid) and bitter. Wines rarely have a salty taste. Each is sensed in a different part of the mouth: sweet at the tip of the tongue; sour or acid along both sides of the tongue, and bitter in the back center of the tongue. This is why it is important that you roll the wine around in your mouth -- so it contacts all the taste sensors. The sweet taste in wines is due primarily to sugar. Sweetness is not necessarily a virtue nor is it a fault; it depends entirely on the character of the wine and the preference of the consumer.
A wine with high levels of acid may taste tart or have a "bite" to it. Acid is natural to wine, an essential flavor component. With too little acid, it will taste flat, or "flabby". We say that an acidic wine is "lemony" or "crisp". A truly sour wine (similar to lemonade with too much lemon in it) is rare, and is considered a serious flaw.
REMEMBER: The opposite of sweet is dry (not sour) and refers to the lack of residual sugar. A wine with high natural acidity is tart or crisp, never sour. A sour wine is one well on its way to being spoiled
The bitter taste in wines is due to tannin. Tannin is a natural flavor component of wine, found in the skins, stems, and seeds. Since white wines have very low tannin content (because of little skin contact during fermentation), they are generally free of a bitter taste. It is common in red wines, particularly young red wines, that the tannin content is high enough (due to extraction from the skins) to be noticeable to the taste.
Now to the last, and most enjoyable, of our five "S's". Let the wine sit on your palate for a few moments before you swallow it. And then, "savor" the wine and its aftertaste.
A good wine will always leave a pleasant aftertaste in your mouth, after you have swallowed. If the aftertaste is bitter, or hot (too alcoholic), or metallic, or cloying (too sweet) or in other ways unpleasant, the wine is flawed.
Wines also have "feel" in the mouth, which we often describe as "body". A light-bodied wine (like most of ours) actually feels light on your tongue. A heavy-bodied red wine, like a Cabernet Sauvignon, will feel fuller - we say it has "weight" in the mouth. These are tactile sensations, rather than sensory, but they are still part of the overall wine evaluation process.
Astringency is another tactile sensation, relating to the "feel" of wine in the mouth, and has a direct relationship to tannin content. The feel in the mouth resembles a persimmon in its "puckeriness". A smooth wine is one lacking in astringency (and therefore lower in tannin) and a "rough" one is too high in this characteristic.
"See", "swirl", "smell", "sip", "savor". The five "S's" of sensory evaluation. With a little practice, you should soon be a certified expert wine taster! Remember that despite the distinctions between the smell and taste stages of wine evaluation, it is the combination of these nasal and tongue reactions that define flavor.