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When you visit Napa Valley during harvest or “crush,” the terms used by people in the local industry may be unfamiliar or even different from what you think they are. Here are popular terms you may encounter with a special emphasis on local usage.

Acidity: One of the key measures of a grape is its acidity. Too little and the wine tastes bland and may spoil easily. Too much and the wine tastes sharp. In general, grapes grown in warm climates like Napa Valley are relatively low in acid. It is often augmented by winemakers for better balance. The typical level in a table wine is 0.6 to 0.7 percent (6 to 7 grams per liter).

Air lock: An air lock is a device that lets carbon dioxide produced during fermentation out of a closed tank but prevents air, which could oxidize wine, or undesired bacteria and yeasts from entering the tank. You can see locks bubbling on tanks and barrels early in the fermentation process.

Alcohol:  A hydrocarbon containing carbon, hydrogen and oxygen atoms arranged in a certain pattern. The alcohol present in beverages is ethanol. Other alcohols like methanol (wood alcohol) and isopropyl are toxic.

American Viticultural Area: The American version of an appellation. It specifies a geographic area like Oakville but not grape varieties that can be grown or any production or quality standards as is common in Europe. The term supposedly implies distinctive wine, but really is used primarily for marketing purposes.  

Barrel: Most red wines here are aged in roughly 59-gallon oak barrels, and some white wines are fermented in as well as aged in them. The barrel, which is lightly toasted inside, imparts flavors of vanilla from the wood and caramel from the toasted sugars, and allows slow and desirable oxidation. Europeans call them barriques.

Barrel thief: A barrel thief is a long bent glass tube used to remove a small sample of wine from a barrel for tasting or testing.

Bin: Grapes are picked into bins. Small bins are more desirable since grapes at the bottom of big bins can be crushed prematurely and start fermenting or even spoil. Half-ton plastic bins are often used to ferment small lots of wine.

Biodynamic: Biodynamic farming was codified by the Austrian theosopher Rudolf Steiner. He combined traditional practices like use of compost, animal manure and planting and managing vines by phases of the moon with an array or teas and portions he called preparations that are applied homeopathically to plants.Some are controversial, like cow manure buried in cow horns at certain phases and similarly dug up, then stirred in a specific matter to produce vertexes before sprinkling on plants. Though having undergone almost no scientific testing, Biodynamic farming has been adopted by many growers and winemakers, some of whom produce superb wine. 

Blend: Many of the world’s most famous wines are blends of different grapes that complement each other. They are not necessarily inferior to wines made from single varieties of grapes.

Botrytis cinerea or noble rot: Botrytis cinerea is a fungus that dehydrates and shrivels grapes leaving berries very high in concentrated sugar. They are used to make distinctive sweet dessert wines.

Brettanomyces: Brettanomyces (British fungus) is a strain of yeast that gives Heineken and some Belgian beers its distinctive character. It can contaminate wine with a barnyard smell, but some people think it provides an appealing complexity in small concentrations.

Brix: Brix is the percentage of sugar in a liquid solution by weight. Grapes are typically picked for table wines at 22 to 26 Brix. A rough approximation of the alcohol produced is 55 percent of that number.  Sparkling wines are picked at lower Brix levels when the grapes are more acid for flavor and because sugar is added to the wine during a second fermentation to create the bubbles.

Bung: A bung is a large stopper – now usually made of silicone – used to seal barrels.

California sprawl: A traditional form of growing grapes that lets the vine canes sprawl around the vine without training to supports.

Cane pruning:  Cutting one or two canes from a vine’s previous year’s growth back to a few buds that will produce the next season’s canes and grape bunches. Contrasts with cordon or California sprawl.

Carbon dioxide: Yeast breaks sugar in grape juice into alcohol and carbon dioxide. The latter is normally released into the air but some is retained for sparkling wines. Carbon dioxide emissions are culprits in pollution and global warming, but grapevines and other plants in vineyards absorb much of that carbon dioxide. 

Cave: A wine cave is a tunnel dug to store wine, and occasionally for production.

Chai: A barrel storage facility above ground.

Cordon training: Cordon trained vines have one or two woody arms extending from the top of the trunk. Short spurs extend from them, each with one or two buds that will form canes.

Cork: A traditional wine closure made from the bark of the cork oak tree. Most comes from Portugal and the Mediterranean. Corks allow subtle aging of wine, but can be contaminated with tricholoanisole (TCA) and its relatives, causing the wine to be “corked.”

Custom crush facility: A custom crush facility or custom winery produces wine for others. Many of Napa Valley’s most noted small-volume wines are made in these shared facilities.

Crush: Crush means to break open the grapes to make them easy to ferment or press to extract juice. Many people confuse crushing and pressing; the famed statue at the bottom of Napa Valley shows a grape presser, not a crusher. Many wineries actually only remove the stems from grapes using a destemmer, but most crushers can serve this function with adjustments. Crush is also local slang for the harvest period when grapes are crushed.

Dry: “Dry” in wine terms means not sweet, though wines with 1/2 percent sugar can still be considered dry as they may not taste sweet to drinkers, particularly if the wine is acid.

Dry farmed: Grown without irrigation. Napa Valley gets enough water to grow grapes, but most falls as rain in the winter. Fortunately, the Napa Valley floor covers an abundant aquifer, and vines can be trained to access it. In other parts of the valley, irrigation is vital, but it can also be used to manage grape yield and ppoperties.

Enologist: In local use, a person who works in a winery wine lab. Elsewhere, a winemaker.

Estate winery: A winery that produces grows grapes and produce its wine on its own property. Most wineries buy grapes from independent growers and other wineries.

Fermentation:  The conversion of carbohydrates like sugars to alcohols and carbon dioxide or organic acids using yeasts or bacteria under anaerobic conditions (lack of oxygen). It is one of the most important natural processes. It creates wine, beer, bread, cheese, yogurt, pickles, sauerkraut, kimchi, soy sauce and many other important foods. In wine, natural sugars are converted to alcohol and carbon dioxide.

Grapes: Many varieties of grapes exist. Those used to make wine here and in most winegrowing regions are in the large vitis vinifera family. They are green, pink or dark, generally called white or red. The color in most red grapes is only in the skin. The juice is clear and the pigment from the skin is extracted by soaking in alcohol, hence red wine is created by fermenting the crushed grapes with their skins. For white wines, only the juice is fermented. For pink wines, the must is only kept in contact with the skins a short while.

Gravity feed: Many winemakers prefer to let grapes, crushed grapes and wine flow by gravity rather than pumping it, which can crush seeds and extract undesired tannins or heat the wine.

Harvest: The process of collecting ripe crops. Most grapes in Napa Valley are harvested by hand, but modern machines can perform the job efficiently and deliver almost perfect grape berries to the winery. It also allows harvesting at night, when the grapes are cool, which is desirable. This will become more widely used as labor shortages develop.

Late-harvest wine: These are made from grapes that have been left on the vine longer than usual. They are usually sweet or dessert wines.

Lees: Lees are dead yeast dells and other wastes that settle to the bottom of barrels and tanks. They can contribute “mouthfeel” (thickness) and desired flavors to the wine.

Malolactic fermentation (MFL): A natural process that lowers acidity by converting malic acid to lactic acid and carbon dioxide. Many winemaker initiate MLF in white wines and almost all red wines  undergo MLF by themselves. In addition to reducing acidity (rarely needed in warm Napa Valley), MLF also introduces a “buttery” flavor, particularly noticeable in white wines like chardonnay.

Meritage: Blended wines on the Bordeaux model. The term was developed for wines that don’t contain at least 75 percent of one grape variety. The red blend is made from at least two of the eight Bordeaux grape varieties while white meritage is a blend at least two of sauvignon blanc, sauvignon vert and semillon. The term is losing popularity to proprietary terms.

Microoxygenation: A judicious application of oxygen to soften flavors and remove undesired substances in wine. Traditionally it is accomplished in barrels, it can be produced by bubbling a tank amount of air or oxygen through wine.

Must: Must is grape juice on the way to becoming wine.

Negotiant: A person or company that buys bulk or semi-finished wine, finishes and packages, then markets it.

Oak alternatives: Oak barrels are very expensive. The best from France cost more than $1,000 each and can only be used a few times to extract flavors. Winemakers often mimic their flavors by inserting oak chips and sticks in used barrels or stainless steel tanks, particularly for moderately priced wines.

Off-dry: Off-dry refers to wines that are slightly sweet. Many popular American wines are off dry in truth though marketed as “dry.”

Organic: In farming terms, organic refers to plants grown “naturally” using only derived from living sources (like compost) and naturally occurring minerals, not synthetic fertilizers, pesticides, herbicides and other chemical.

Oval: An oval is a large upright tank traditionally used for aging wines.

Oxidize: Oxygen can combine with other materials to oxidize them. Rust is an example. If wine is oxidized, it turns brown and becomes undesirable. Very subtle oxidization can eliminate undesired odors, however.

pH: The measure of hydrogen atoms in a solution, a type of measure of acidity. Water is neutral at 7, and lower numbers indicate acid conditions, while higher are alkaline. It its pH is too high, wine is likely to spoil. A typical pH for a wine is 3 to 3.5.

Press: As a noun, it’s the machine used to extract juice or wine from grapes with pressure. The venerable basket press is a good example, although most wineries use sophisticated presses in which a bladder filled with air squeezes the grapes against the walls of a cylinder. As a verb, the act of pressing grapes. Also see crush.

Pump over: The cap of grapes that rises is a fermenting tank must be kept moist. One way it to pump wine from near the bottom of the tank over it.

Punch down: The cap of grapes that rises in fermenting red wine must be kept wet. One way is to punch it down in an open tank with a special tool.

Puncheon: A large wine barrel.

Racking: Racking wine is pumping or draining it off settled lees (dead yeast cells and other waste) and putting it in another or the same cleaned container.

Reductive or reduced wine: A stinky wine contaminated with sulfides. Can often be corrected with careful oxidation or even decanting.

Refractometer: A refractometer is a simple instrument for measuring the Brix (sugar content) or grape juice (must) using refracted light.

Reverse osmosis: Reverse osmosis systems are used to remove defects and excess alcohol from wines.

Sorting table: Many wineries now use a sorting table to remove defective grapes, stems (jacks) and material other than grapes (MOG) like leaves and lizards before fermenting grapes. The most modern are automated and operate automatically, but most use conveyor belts or shaker tables and patient humans to remove debris.

Spinning cone: A low-pressure low-temperature still used to remove alcohol from wine, whether to make a wine without alcohol or to reduce the alcohol level of wines.

Structured wine: Winemaker jargon for tannic wine, a term considered pejorative.

Sulfate: Copper sulfate is sometimes added to wine to remove stinky sulfides.

Sulfide: Sulfides are nasty-smelling compounds that sometime form in wine. They include hydrogen sulfide, which smells like rotten eggs, and related compounds like mercaptan, which smells like rotten cabbage at best.

Sulfite: Sulfites are used to protect wine, killing unwanted bacteria and yeasts. They can be introduced by burning elemental sulfur to create sulfur dioxide gas, introduced as a gas, or commonly, created by dissolving  potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium metabisulfite or sodium sulfite in the wine.  Small quantities of sulfites are used, and have been used for millennia. They are also used to preserve many other foods including dried fruit. Few people appear to be allergic to sulfites in spite of the required warning labels, and it’s challenging to make a long-lasting wine without using them.

Sulfur: Elemental sulfur dust is sprayed on vines to protect grapes from fungus and mildew. If sulfur is burned, it gives off sulfur dioxide. Burning sulfur “candles” in barrels was once used to disinfect them.

Sulfur dioxide: See sulfite; a generally harmless disinfectant for wine and food.

Tank: Large vessels, generally now made of stainless steel, used for fermenting, aging, blending and storing wine. Historically, wood and concrete tanks were used, and they are making a bit of a comeback for perceived advantages like temperature stability and induced convection currents, particularly in concrete “eggs.”

Tannin: Tannin are bitter polyphenols found in grape skins, seeds, stems and some juice. They are also found in oak barrels. Tannins contribute age-worthy properties and complexity to wine, but many people find them very distasteful. They may also contribute healthful properties to wine.

Tricholorosanisole (TCA): Tricholorosanisole is an earthy, wet-Airedale-smelling contaminant generally introduced from defective corks, hence such spoiled wines are called “corked.” Wine drinkers vary dramatically in sensitivity to these smells.

Toast: Oak wine barrels are “toasted” like bread to a varying degree to mellow their tannins and provide desired flavors. This is less extreme than the charring of whiskey and rum barrels, which contributes color as well as caramel flavors to the spirits.

Topping off: Replacing the wine that inevitably evaporates or is absorbed in wooden wine barrels.

Vat: A tank.

Varietal/variety: There are many varieties of grapes. Varietal is the adjectival form; it’s correct to refer to a varietal wine produced mainly of one variety, but not to refer to grapes or vines as varietals.

Vineyard: A farm that grows grapes.

Vintner: In Napa Valley, the owner of a winery. Elsewhere, a wine merchant. In general, not the actual winemaker.

Virtual winery: A company that produces wine from bought grapes in a rented facility or has the wine produced for it. Legally, a wine retailer that can also distribute its wines. 

Winemaker: The person who actually makes the wine; not usually the owner of the winery.

Winery: A company that produces wine or the building used to produce wine.

Yeast: Wine yeasts are tiny Saccharomyces cerevisiae fungi used to ferment wine (other strains used for beer or bread). Most winemakers inoculate their musts (grape juice) or crushed grapes with carefully incubated strains, but some depend on “feral” yeasts present everywhere in winemaking regions and wild yeasts on grape skins. True wild yeasts may introduce off-odors and can’t ferment all the sugar in a typical wine, but they can introduce complexity, though Saccharomyces cerevisiae is needed to complete the process and make a stable dry wine.

The Wine Advocate publishes a good glossary of terms primarily related to wine tastes and smells at

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