AA MEASURES K

The Beringer vintner uses an atomic absorption (AA) spectrometer to measure potassium while the wine is aging. Kantz explains, "Grapes take up potassium from soils as they ripen, and potassium is therefore an important cation in wine. Potassium exchange for hydrogen ions affects pH in grapes, and the potassium level in wine also affects the tendency of potassium bitartrate to precipitate. Thus, by measuring potassium, we can get some insight into how much potassium bitartrate will precipitate during aging."

At Topolos, the emphasis is on acetic acid levels. "It is a benchmark that enables you to see a voluntary metabolite go up long before you can taste it," Jacobs says. "If the smell changes, it can indicate that the wine has a hydrogen sulfide problem. The quickest solution is to rack and aerate the wine, but that is not a permanent fix. We'll use Vinquiry for testing in this type of case."

Before the final bottling, wine may be filtered or undergo "fining" to be clarified and stabilized as part of the finishing process. Filtering removes bacterial sludge. Unfiltered wine may be the darling of wine critics, but it also is more sensitive and susceptible to spoilage. Heat and cold stabilization are used to remove unstable proteins and tartrates, respectively. For instance, during cold stabilization, the sample is frozen and then closely monitored as it thaws. 'We're looking for crystals or tartrates," explains Jacobs. "Tartrates, which occur mostly in white wines, are undesirable because they affect the stability of the wine. Because the wines sit in refrigeration a lot, we want to ensure that the character doesn't change over time. We prefer not to filter the wine whenever possible."

The industry is shifting to less and less filtering of wines," Kelly observes. "But this requires a corresponding culturing and monitoring of the wines prior to bottling to evaluate microbial status for any spoilage organisms and sediments, and focus on finishing operations." Vinquiry provides filtration analysis to determine the filterability of wine, to minimize manpower, and to optimize the filter media. The company also offers different fining trials and proteins to clarify the wine and modify the mouth feel.

Fining also clears the wine of any remaining particles before bottling, but the process is a bit more complicated than filtering. It may be as simple as the use of beaten egg whites, or as complex as the introduction of fining agents such as enological gelatins. These gelatins are made of protein and polypeptidic fractions manufactured through the hydrolysis of collagen or fibrous proteins in biological tissues. Gelatin is most commonly used just before bottling, and its chemical interaction with the wine adjusts the level of tannin and modifies flavors, aromas, bitterness, and astringency. The enologic gelatin bonds with certain protein chains to coagulate and filter out sediments and other wine components. However, as with yeasts, each fining gelatin works somewhat differently. The more it is used to soften the wine, the more tannins and color tend to be removed.

MORE THAN MECHANICAL

Once the wine has been aged, it is blended and bottled. Unlike other beverage bottling processes, wine bottling is more than a mechanical operation. 'Me quality of the cork and the color and shape of the bottle are of utmost importance at this stage, because these factors can greatly affect the wine. Dark glass acts as a light filter and protects wine from ultraviolet and infrared rays. Bottles with narrow necks and deep bodies naturally hold back the sediment of an unfiltered wine on pouring.The cork, however, is the main focus at this stage, because it must provide a perfect seal without tainting the flavor of the wine. Wineries invest considerable research in analyzing and purchasing only the highest quality cork. "Cork is a big issue, mainly because of cork taint," Kelly notes. "We look for mold, lignum, and anisole or chlorine. We're looking for chemical reactions at levels less than a drop of water in a swimming pool, but poor quality cork can impart a musty, sticky aroma to wine."

"During bottling," Kelly continues, "we check the sugar level and ensure that there is no yeast in the finished product We also check the alcohol level and provide an alcohol certificate based upon our findings." All wine must be tested before bottling, and the final results must be provided to the Bureau of Alcohol, Tobacco, and Firearms (BATF) by a BATF-certified lab (Vinquiry is a BATF-certified lab, as is Beringer's lab). Some of this information must be

Research has shown that monoterpenes in the grape contribute to the flowery, fruity flavor characters that the wines of Muscat varieties often exhibit. Varieties such as Sauvignon Blanc and Cabernet Sauvignon exhibit vegetal characteristics because of a compound called pyrazene. However, for most nonfloral varieties (i.e., those not of the Muscat family, such as Chardonnay), the grape-derived volatiles important to wine flavor are basically unknown.

Given the gaps in knowledge about wine, it is hardly surprising that the science of winemaking focuses on the chemistries that affect fermentation. 'Me steps that are taken during this key stage are all geared toward delivering an end product that meets with consumer approval. However, the efforts of the winemaker and the wine lab may well be underappreciated because, regardless of the chemistry involved, personal tastes differ. Nevertheless, the experts offer the following tips to ensure that the consumer gets the most satisfaction from the end product.

Analysis of wine involves key steps that seek to determine four sensations: visual, olfactory, degustatory, and tactile.

Visual. When sampling a wine, first observe the color and determine whether the wine is clear or cloudy. Clarity and a visually stimulating color are desirable.

Olfactory. Next, swirl the wine and take a sniff. Swirling the wine releases its aromas. Although people can taste only four flavors, most people can identify some 5,000-8,000 odors. Aromas indicate whether the wine is free of flaws, such as excessive sulfur or cork taint, and how flavorful the wine is.1be flavor quality of a wine is judged on a subjective determination of the aromas' desirability, complexity, and depth.

Degustatory. Now, taste the sweet, salty, sour, and bitter flavors of the wine. Too much alcohol provides a burning sensation at the back of the palate. Tannin imparts a dry, oaky, rough flavor and feeling (similar to tea) that dries up the saliva. Even though acid is a bitter flavor, it enhances wine by helping to develop the natural fruitiness and crispiness in the flavor. If the wine is flat, it doesn't have enough acid. A fruity wine will have 1- to 5-percent residual sugar. Despite fermentation, all wines have a touch of sugar, but the fruitiness-rather than the sugars should be most apparent.

Tactile. Finally, feel the viscosity of the wine on the tongue, and test the body. Savor the tactile sensation that the wine provides.

The winemaker's goal is to provide a pleasurable combination of the four sensations and a balance of the four flavors. Achieving this balance is the point of all the chemical monitoring and analysis that goes into wine production.

As Jacobs points out 'When it comes down to it the consumer doesn't care about the chemistries, just what the wine tastes like." No matter how well the winemaker or wine lab manager performs the analytical tasks associated with the wine's chemistry, the consumer has the final say on the result of months-even years-of work. Perhaps this reason alone is why winemaking is as much an art as a science.

HELEN GILLESPIE is an industry analyst, editorlpublisher of the LIMS/Letter, and Webmaster of the LIMSource. Can be reached at RO. Box 935, Kenwood, CA 95452. Tel.- 707-833-6885; Fax.- 707-833-6865,- E-mail: Webmaster@LIMSourcexom; Web: http://www.LIMSource.com