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Glossary

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Search results for: Fermentation

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Alcoholic Fermentation: Also called primary fermentation, this is the process in which yeasts metabolize grape sugars and produce alcohol, carbon dioxide and heat. The final product is wine.
Fermentation: Fermentation The process by which yeast converts sugar into alcohol and carbon dioxide; turns grape juice into wine.
Malolactic Fermentation (ML): Malolactic Fermentation (ML) A bacterial conversion occurring in most wines, this natural process converts sharper malic acid (found in green apples) into softer lactic acid (found in milk). Total acidity is reduced; the wines become softer, rounder and more complex. In addition, malolactic fermentation stabilizes wines by preventing an undesirable fermentation in the bottle. Often called the secondary fermentation. Frequently associated with big, rich, buttery Chardonnay, malolactic fermentation is prevented when fresher, crisper styles are desired.
Secondary Fermentation: The process that creates the bubbles in sparkling wine. As the wine is bottled, a small amount of yeast and sugar is added before the bottle is sealed with a sturdy crown cap. The yeasts quickly start fermenting the sugars, producing alcohol and carbon dioxide. Since the gas cannot escape, it dissolves into the wine.
Temperature of Fermentation: As yeasts convert grape sugars into alcohol, they also produce heat. Excessively high temperatures can kill the yeasts and make the wine’s fruit flavors seem stewed or dull, whereas cooler temperatures maintain the freshness of the fruit. Just the right amount of warmth can contribute a richer, rounder mouthfeel.

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Alcohol: Ethyl alcohol, a chemical compound formed by the action of natural or added yeast on the sugar content of grapes during fermentation.
Barrel Fermented: Denotes wine that has been fermented in small casks (usually 55-gallon oak barrels) instead of larger tanks. Advocates believe that barrel fermentation contributes greater harmony between the oak and the wine, increases body and adds complexity, texture and flavor to certain wine types. Its liabilities are that more labor is required and greater risks are involved. It is mainly used for whites.
Bitter: Describes one of the four basic tastes (along with sour, salty and sweet). Some grapes—notably Gewürztraminer and Muscat—often have a noticeable bitter edge to their flavors. Bitterness can also be imparted by the use of underripe or green stems during the fermentation and aging processes. If the bitter quality dominates the wine's flavor or aftertaste, it is considered a fault. In sweet wines a trace of bitterness may complement the flavors. In young red wines it can be a warning signal, as bitterness doesn't always dissipate with age. Normally, a fine, mature wine should not be bitter on the palate.
Blanc de Noirs: Blanc de Noirs "White from blacks," meaning a white wine made of red or black grapes, where the juice is squeezed from the grapes and fermented without skin contact. The wines can have a pale pink hue. This term is used for Champagne that is made entirely from Pinot Noir and/or Pinot Meunier instead of a mix of both red and white grape varieties.
Carbonic Maceration: Carbonic Maceration Most frequently associated with Beaujolais, this is a method of producing light-bodied, fresh and fruity red wines. Instead of crushing the grapes and releasing the juices to be fermented by yeasts, whole grape bunches are placed in a tank and the oxygen is displaced by carbon dioxide. Fermentation starts on an intracellular level inside the berry, producing some alcohol as well as fruity aromatics. In practice, the weight of the grapes on the top crushes the grapes on the bottom and yeasts ferment the juice; the wine is partly a product of carbonic maceration and partly of traditional yeast fermentation.
Chaptalization: Chaptalization The addition of sugar to juice before and/or during fermentation, used to boost sugar levels in underripe grapes and alcohol levels in the subsequent wines. Common in northern European countries, where the cold climates may keep grapes from ripening, but forbidden in southern Europe (including southern France and all of Italy) and California.
Charmat: Charmat A less expensive, mass-production method for producing bulk quantities of sparkling wine. The second fermentation takes place in a pressurized tank, rather than in a bottle, decreasing lees contact and producing larger, coarser bubbles. The wine is filtered under pressure and bottled. Also known as the bulk process or tank method. Wines made this way cannot be labeled méthode Champenoise.
Cloudiness: Lack of clarity to the eye. Fine for old wines with sediment, but it can be a warning signal of protein instability, yeast spoilage or re-fermentation in the bottle in younger wines. Cloudiness may also represent a deliberate choice by the winemaker not to filter a wine.
Disgorgement: When making sparkling wine, this technique is used to remove frozen sediment remaining in the bottle after the second fermentation. Through the riddling process, the sediment settles in the bottle neck and the neck is then dipped into a brine solution and frozen. Working quickly, the bottle is turned upright and the crown cap removed. The plug of frozen sediment is ejected by the pressure of the carbon dioxide. Also known as Dégorgement.
Dosage: Dosage In bottle-fermented sparkling wines, a small amount of wine (usually mixed with sugar) that is added back to the bottle once the yeast sediment that collects in the neck of the bottle is disgorged. Also known as liqueur d'expedition.
Filtering: Pumping wine through a screen or pad to remove leftover grape and fermentation particles. Most wines are filtered for both clarity and stability, although many winemakers believe that some flavors and complexity are also stripped from the wine.
Lees: Lees Sediment—dead yeast cells, grapeseeds, stems, pulp and tartrates (harmless tartaric acid crystals)—remaining in a barrel or tank during and after fermentation. Immediately following fermentation, wine should be racked off of the gross lees, the large particulate matter such as seeds, skins and stems, which are rich in spoilage organisms. The wine may be aged for an extended period on the fine lees, however, in what's called "sur lie" aging. Fine lees, the dead yeast cells leftover from fermentation, can enhance an aging wine with added richness, flavor and aroma complexity, and can also bind with excess tannins.
Maceration: Maceration This process, used primarily in making red wine, involves steeping grape skins and solids in wine after fermentation, when alcohol acts as a solvent to extract color, tannins and aroma from the skins (aided by heat, the amount of skin contact and time). Cold maceration (steeping when the must is not heated), takes place before fermentation.
Made and Bottled By: On U.S. labels, this indicates only that the winery crushed, fermented and bottled a minimum of 10 percent of the wine in the bottle.
Malic Acid: Malic Acid A sharp, tart acid found in grapes as well as in green apples. Less-ripe grapes or grapes grown in cooler climates can contain high levels of malic acid; the resulting wines often contain aromas and flavors reminiscent of green apples. It is converted to smoother lactic acid during malolactic fermentation.
Press Wine (or Pressing): The juice extracted under pressure after pressing for white wines and after fermentation for reds. Press wine has more flavor and aroma, deeper color and often more tannins than free-run juice. Wineries often blend a portion of press wine back into the main cuvée for added backbone.
Produced And Bottled By: Indicates that the winery crushed, fermented and bottled at least 75 percent of the wine in the bottle.
Smoky: Usually the result of fermenting or aging in oak barrel, a smoky quality can add flavor and aromatic complexity to a wine.
Stemmy: Describes a wine with green flavors of unripe fruit or wood, frequently a result of a wine being fermented too long with the grape stems.
Sur Lie: Sur Lie Wines aged sur lie (French for "on the lees") are kept in contact with the dead yeast cells and are not racked or otherwise filtered. This is mainly done for whites, to enrich them. (It is a normal part of fermenting red wine, and so is not noted.) The concept originated in Burgundy, with Chardonnay, but is now popular around the world with numerous white grape varieties. Sur lie aging can be overdone, leading to an off-putting leesy flavor.
Tartrates: Tartrates Harmless crystals resembling shards of glass that may form during fermentation or bottle aging (often on the cork) as tartaric acid naturally present in wine precipitates out of solution. Components of tartaric acid, including potassium bitartrate and cream of tartar, they are less soluble in alcoholic solutions than in grape juice and solidify at cooler temperatures (such as those found in a refrigerator); can be avoided in finished wines through cold stabilization. Decanting and careful pouring can prevent transferring the crystals from the bottle into the glass.
Yeast: Micro-organisms that convert sugar to alcohol and carbon dioxide in the process known as fermentation. The predominant wine yeast, saccharomyces cerevisiae, is the same micro-organism that ferments beer and makes bread dough rise.
Auslese: Auslese German classification based on the ripeness level and sugar content of the grapes. Auslesen are made from individually-selected bunches of very ripe grapes that have higher sugar concentrations than those selected for spätlesen, but lower than those selected for beerenauslesen. Auslesen are nearly always sweet wines but can be fermented in drier styles.
Cap : The thick layer of skins, stems and seeds that forms at the surface of fermenting red wine. Cap management, or breaking up the cap to increase contact between the skins and the liquid, is important since red wines extract color and flavor from the skins.
Élevage: Élevage French term for the progression of wine between fermentation and bottling. Comparable to the term "raising" in English; think of élevage as a wine's adolescence or education. The raw fermented juice is shaped during this period into something resembling its final form, through techniques such as barrel aging, filtering and fining. Good winemaking decisions during élevage can help the juice achieve its full potential; bad decisions can leave it flawed.
Glycerin: Glycerin Produced during fermentation, glycerin contributes to the wine’s body.
Lactic Acid: A smooth (not sharp) acid created during malolactic fermentation. This acid is also found in milk.
Native Yeast: Also known as indigenous or wild yeasts, these are yeasts that occur naturally on the grapes or in the cellar, rather than commercially cultured yeasts; both are used for fermentation. Some argue that native yeasts are more authentic, but most producers favor the reliability of cultured yeasts.
Organic Wine: The rules and methods for producing organic grapes and wine are still evolving. The answer usually depends on the country of origin and the various governing organizations involved. France, for example, legally defined organic farming in 1981 as "farming which uses no synthetic chemical products." In most cases, organic wines are fermented from grapes grown without the use of synthesized fertilizers, pesticides or herbicides. In organic wines, natural yeasts and minimal amounts of sulfur are often used in the fermentation process.
Pomace: Pomace The mass of grape solids—skins, stems and seeds—remaining after pressing (for whites) and after the wine has been drained from the fermentation vessel (for reds).
Punch-Down: Also known as pigéage, the process of breaking up the thick layer of skins, stems and seeds that forms at the surface of fermenting red wine and submerging it during fermentation to extract color, tannins, flavor and aromas from the grape solids.
Pump-Over: Also known as remontage, the process of pumping red wine up from the bottom of the tank and splashing it over the top of the fermenting must; the purpose is to submerge the skins so that carbon dioxide is pushed to the surface of the must and released.
Recently Disgorged: Indicates that the lees have been removed from a sparkling wine just prior to release. After sparkling wine has undergone the second fermentation in the bottle, the wine can remain on the lees for many years to develop additional complexity and richness.
Riddling: In making sparkling wine, the process of moving the sediment remaining in the bottle from the second fermentation to rest in the neck of the bottle for easy removal. The process of riddling is part of the méthode traditionelle and was developed by Madame Clicquot (Veuve Clicquot) in the early 1800s to remove the cloudy lees from the bottles. The bottles are loaded in a horizontal position onto wooden racks called pupitres. At this point, the sediment rests on the side of the bottle. As the bottles are riddled, or given a sharp quarter-turn daily and gradually tilted upside-down, the sediment works its way to the bottle neck. Today, most producers use efficient mechanical riddlers. Also known as Remuage.
Saignée: Saignée A French term meaning literally "to bleed," saignée refers to the process of bleeding or pulling juice from a tank of red must that is just beginning fermentation. The goal is two-fold. First, the lightly-colored juice that is bled out of the tank produces a rosé. Second, the must remaining in the tank has a higher proportion of grape skins to juice; the resulting wine will be richer and more concentrated.
Skin Contact: Refers to the process of grape skins steeping in juice or fermenting must to impart color and flavor to the wine.
Sulfites: Winemakers all over the world use sulfur dioxide to clean equipment, kill unwanted organisms on the grapes and protect wines from spoilage. A tiny amount remains in the bottle, and U.S. label laws require a statement to announce its presence. Sulfites also occur naturally during fermentation process.
Tank Method: Also known as charmat, a less expensive method for making sparkling wine. The tank method is used to produce bulk quantities of inexpensive sparkling wines. The second fermentation takes place in a pressurized tank, rather than in a bottle, decreasing lees contact and producing larger, coarser bubbles. The wine is filtered under pressure and bottled. Wines made this way cannot be labeled méthode Champenoise.
Transfer Method: Technique for making sparkling wine in which, after the second fermentation in the bottle and a short period of sur lie aging (but before riddling), the wine is transferred—with sediment—to a pressurized tank. The wine is then filtered under pressure and bottled. With the enormous savings in labor and time, the wines are slightly less intense and less creamy than those produced using the more time-consuming and expensive méthode Champenoise.
Délestage: Délestage French term for racking and returning a wine back to the tank. Wine is pumped out of the fermenting tank and back over the cap to facilitate extraction of color and flavor.
Micro-oxygenation: This technique, used almost exclusively on red wines, allows winemakers to control the amount of oxygen that wines in tank are exposed to. The apparatus involves chambers connected by tubes and valves to an oxygen tank. Small, measured amounts of oxygen are allowed to pass through the wine via a porous stone or ceramic plate at or near the base of the tank. The benefits of this type of oxygen exposure include prevention of oxidation and reduction as well as promotion of healthy yeast cultures, which prevent stuck fermentations. Micro-oxygenation is also believed to soften tannins and, in conjunction with the use of oak chips, is frequently practiced as an alternative to oak barrel aging.
Vinification: Loosely synonymous with "winemaking," the act of creating wine from grapes, beginning with the crushing of grapes at harvest and ending when the fermented juice is barreled.
Winemaking: Largely synonymous with "Vinification," winemaking is the process by which harvested grapes are crushed, fermented (and otherwise manipulated through yeast inoculations, temperature control, punch-downs, pump-overs, racking, oak-chip additions, filtering, etc.), aged in barrel, steel tank or other vessel, and finally bottled.
Méthode Traditionnelle: The labor-intensive process whereby wine undergoes a secondary fermentation inside the bottle, creating bubbles. The process begins with the addition of a liqueur de tirage (a wine solution of sugar and yeast) to a bottle of still base wine, triggering a secondary fermentation inside the bottle which produces both carbon dioxide and spent yeast cells, or lees, which are collected in the neck of the bottle during the riddling process. The lees are then disgorged from the bottle, and replaced with a solution of wine and sugar, giving the sparkling wine its sweetness. All Champagne and most high-quality sparkling wine is made by this process. Also known as méthode Champenoise, méthode classique and metodo classico.
Press: After fermentation, the mixture of red grape juice, skins, lees and other solids is pressed to separate the juice from the solids. Because extended skin contact is undesirable for white wines, white grapes are pressed before fermentation.
Devatting: Also known as délestage, the oxidative winemaking process in which, after the cap of grape musts, skins, seeds and stems forms on the top of a vat of fermenting wine, the wine is drained through a valve at the base of the tank into another vat and reserved while the remaining solids are allowed to drain for a few hours. The reserved wine is then pumped back into the original tank over the top of the drained skins, seeds and stems. Like punch downs and pump overs, the purpose of devatting is to increase the extraction of color, flavor, tannins and aromas from the solids, as well as aerate the fermenting wine.
Must Weight: Measurement of the sugar content in grape must, or unfermented grape juice, which indicates the potential alcohol of the juice were all of the sugar to be converted to alcohol during fermentation. Like Brix, Baumé and Oechsle, must weight is more accurately a measurement of the must's density or specific gravity.
Sherry: Sherry is a fortified wine made in Jerez, Spain, most often from the Palomino grape but also from the Pedro Ximénez and Moscatel varieties. Following fermentation, the wine is fortified with distilled wine spirit, up to the minimum strength of 15.5 percent alcohol. The fortified wine is then usually aged in oak barrels arranged in a solera system of multiple vintages, and which may include more than a hundred vintages of Sherry blended together. Sherries may be classified by their quality, age, sweetness and or alcohol contents into categories which include fino, manzanilla, amontillado, oloroso, cream, etc.
Ripasso: Italian term for a process in which dried grapes or leftover grapeskins (pomace) are added to a fermented wine for a period of maceration to increase its intensity, flavor, alcohol and color. This method is used to make some wines from Valpolicella, using the leftovers from the area's Recioto or Amarone wines, made from raisinated grapes dried on mats in the appassimento process.
Orange wines: White wines made with extended grape skin contact during fermentation or maceration, imparting an orange hue to the finished wine, along with tannins. The practice originated thousands of years ago in the Caucasus, but has more recently regained popularity in Italy's Friuli region and the neighboring Brda district of Slovenia.
Ancestral Method: An inexpensive but risky and difficult-to-control method of producing sparkling wine, and almost certainly the oldest, in which the primary fermentation is stopped before completing, and a secondary fermentation occurs in the bottle, ending when the yeast cells deplete the supply of residual sugar. There is no dosage, or sugar addition, to kick-start the secondary fermentation, and the wine is not disgorged to remove any sediment or lees remaining afterward.
Roto-Fermentor: A programmable, mechanized fermenting tank that rotates on an axis to mix the cap and grape must during fermentation to facilitate extraction of color, tannins and flavor.
Tirage: See Liqueur de Tirage.
Liqueur d'Expedition: See Dosage.
Liqueur de Tirage: A solution of wine, sugar and yeast added to a bottle of still base wine to begin the traditional method of making Champagne, or méthode traditionnelle. The addition of the liqueur de tirage triggers the secondary fermentation which gives sparkling wine its bubbles.
Col Fondo: Sparkling wine production method for traditional Prosecco, in which the spent yeast cells, or lees, left over from the secondary fermentation are not disgorged.
Traditional Method: See Méthode Traditionnelle.
Inoculation: The process in which a winemaker introduces yeast to the must to kick-start fermentation.
Whole cluster: This can refer to whole cluster pressing and/or whole cluster fermentation, where pressing and/or fermentation happen without the stems having been removed from the berries.

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