Wine Making Glossary and Definitions

Acetobacter: A group of bacteria that convert wine to vinegar (ethanol into acetic acid) through an aerobic (oxygen present) fermentation.

Acid: A compound found in all grapes and an essential component of wine that helps with preservation, and shapes its flavors plus creates and controls its aftertaste. There are four major kinds of acids found in wine, Citric Acid, Lactic Acid, Malic Acid and Tartaric Acid (the most dominant and important acid in wine grapes).

Acid Blend: A generic name for any commercially available blend of acids (usually citric, tartaric, and possibly malic) sold for the acidification of homemade wines, typically wines made from fresh fruits.

Acrid: A term used to describe a harsh or bitter taste or pungent smell in wine resulting from excess sulfur.

Aeration: The process of incorporating air into wine, must, or juice. Usually by splashing while racking, stirring vigorously, or using a mechanical device such as a Wine Whip or Degasser. This is sometimes done to "blow off" undesirable aromas such as hydrogen sulfide, to give an initial dose of oxygen to a fermentation just getting under way, or to aid in the aging process of wine kits.

Aging: Letting a wine sit for several months to several years, to allow its flavor to properly develop. Aging is often done in oak barrels or in glass carboys.

Airlock: A plastic device that fits into the opening of a carboy or into bung holes of barrels to allow gases produced by wine to escape while keeping out air.

Antioxidant: Compound that retards oxidation and slows its effects in wine (browning, sherry-like aromas). Sulfur dioxide, SO2, is the most widely used winemaking antioxidant. It also serves as an antimicrobial agent.

Astringency: The dry sensation created on the tongue caused by tannin in wine. The tannins actually denature the salivary proteins, causing a rough "sandpapery" feel in the mouth.

Bottle Shock aka Bottle Sickness: A temporary condition characterized by muted or disjointed fruit flavors. It often occurs immediately after bottling or when wines (usually fragile wines) are shaken in travel. Also called bottle shock. A few days of rest resolves bottle shock.

Brix: The amount of sugar in a wine typically measured by a hydrometer, which is a floating instrument that determines the density of solution. Based on a system calibrated to the density of water, the pre-fermentation degrees Brix of most table wines are between 22 and 26, meaning 22 to 26 percent sugar. Knowing the Starting Brix of your juice helps predict the final alcohol percentage.

Bulk Aging: Refers to the aging of wine before bottling and occurs in kegs, barrels or carboys as opposed to the aging that is done in corked bottles.

Bung aka Stopper: The rubber stopper is placed in the neck of a carboy or demijohn that reduces the size of the opening to accept an airlock and to create an airtight seal.

Campden Tablets: A convenient way of delivering sulfites to wine. One tablet contains one-half gram of potassium or sodium metabisulfite.

Cap: Fruit skins, stems, and pulp that float to the surface during fermentation. This cap is "punched down" into the wine one or two times each day to extract tannins and color.

Carboy: A glass or plastic container that looks like an office water-cooler bottle. Carboys typically come in 3, 5, 6, 6.5 and some times 7 gallon sizes and used for secondary fermentation and longterm, bulk aging of wines.

Chaptalize: The process of adding sugar to grape juice that does not naturally possess enough sugar (Brix) to make good wine.

Cold Stabilization: Cooling wine to approximately 32 degrees causing tartrates and other insoluble solids to precipitate prior to bottling. This process is considered more of a quality-control step than a necessity for home winemakers.

Clearing or Clarification: The natural settling-out of small particulates and suspended matter in finished wine over time. The material that settles out to the bottom of the container is called the lees. Often times fining is also referred to as Clearing or Clarification. Technically fining, as described below, is the process of adding agents such as Bentonite or others to help clarify the wine.

Decanting: The process of separating the sediment from a wine prior to drinking by slowly pouring the wine from its bottle into another container.

Dry: At or near zero Brix and/or having no taste of sugar, typically less than 0.5 to 0.7 percent sugar.

Enology: The science of winemaking.

Extended Maceration: Letting the red grapes sit for an extended period of time after fermentation prior to being pressed so that additional flavor, color and richness develops.

Filtering: The process of sending a wine through a filter made of either cloth or paper to remove any remaining sediment or impurities

Fermentation: The anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.

Fining: The process of adding an agent (such as bentonite or gelatin) to help clarify finished wine by removing particles that are in suspension. This operation is done before bottling to help ensure the product will not be cloudy in the bottle or glass.

Flocculates: A general term used to describe the visible particles that float in unfinished wine.

Glycerin: Also known as glycerol, glycerin is a sugar added to wine to increase a wine's body or mouth feel and in higher amounts, sweetness.

Hydrometer: A measuring device that tells you the specific gravity (relative density) or the amount of sugar (in Balling or Degrees of Brix) of a juice or wine. This helps you determine the amount of alcohol in the wine. Hydrometers are calibrated at 60 degrees F and adjustments or compensation will need to be made to readings take of a juice or wine that is warmer or cooler than 60 degrees F.

Invert Sugar: Common sugar (sucrose) that has been broken down into fructose and glucose. It does not contain dextrins. One pound of invert sugar is only two-thirds as sweet as cane sugar, so you have to use 50 percent more to achieve the same sweetness.

Lactic Acid: An acid present in wines that have undergone a malolactic fermentation, in which the malic acid converted to lactic acid by malolactic bacteria. Lactic acid is less acidic than malic acid.

Lees aka Trub: The spent yeast cells and other solids that accumulate on the bottom of winemaking vessels. Lees are removed by multiple rackings during the bulk aging process.

Maceration: The processes through which red wine grape (or other fruit) skins, seeds, and pulp are mixed and mashed in with the fermenting juice to extract tannins, colored compounds, and aroma from the grapes. Different maceration programs have different effects. For example if you stir red wine while it ferments (often called "punching down") twice a day as opposed to once a week, you will extract more color and tannin from the skins and seeds of the grapes into the finished wine than if your strategy was less aggressive.

Malic Acid: A naturally occurring grape acid that decreases with ripening. It is one of the principal components of a wine's total acidity. If a wine is too acidic (the grapes hadn't ripened fully), it can be de-acidified by a malolactic fermentation, in which the malic acid will get metabolized by malolactic bacteria and converted to lactic acid. Many red wines undergo Malolactic Fermentation to soften and smooth the wine.

Malo-lactic Fermentation: Very different than alcoholic fermentation, malo-lactic fermentation occurs when a strain of lactic acid bacteria is introduced by chance or on purpose into a finished grape wine. These bacteria convert the malic acid to lactic acid, a less potent acid, as well as contributing some flavor and aroma to the wine. Usually described as Buttery or Caramel, this Malolactic aromatic profile is especially desirable in quality red wine production as well as some whites, such as Chardonnay.

Mead: A type of wine made by fermenting honey and water.

Must: The original grapes, stems, skins, and liquid that are used to ferment into wine.

Oaking: The process of introducing oak to a wine that is unoaked or lacking oak from its barrel aging. Oaking can be done by adding liquid oak, powdered oak, oak chips or shavings, or staves. Timing of exposure of these oaking products vary greatly from one week to several months depending on the product added, how much is added, and how much oak flavor is needed or desired.

Oxidation: Oxidation occurs when air comes into contact with a developing wine. Usually a fault in a wine, it causes the wine's flavor to change and the liquid to brown.

Pectins: Complex carbohydrate chains naturally occurring in fruits that can contribute to the viscosity and haziness of a wine. They can be shortened and solubilized (dissolved) by Pectic Enzyme, which are often times used in wine making.

PH: A chemical measurement of acidity or alkalinity; the higher the pH the weaker the acid. Used by some wineries as a measurement of ripeness in relation to acidity. Low pH wines taste tart and crisp; higher pH wines taste flat and are more susceptible to bacterial growth. A range of 3.0 to 3.4 is desirable for white wines, while 3.3 to 3.6 is best for red wines.

Primary Fermentation: The main fermentation that turns a container of must or juice into a wine where the yeast converts the raw sugars into alcohol and carbon dioxide. A common misunderstanding is that during primary fermentation the must or juice needs to be protected from outside air. At this stage it is all right your soon to be wine to be exposed to the air because the yeast is producing so much carbon dioxide that it forms a blanket of inert gas over the fermenting juice or must.

Racking: When you transfer wine using siphon hose and other racking equipment from one container to another leaving behind whatever lees and or sediment that has collected at the bottom of the first container.

Rehydration: The process of adding water to dry wine yeast before pitching. Rehydrating wine yeast restores the strength of the yeast to its pre-dehydrated strength. 104 degrees F is the optimal temperature for rehydration of wine yeasts.

Remuage: The technique of gradually inverting champagne bottles at the end of the bottle fermentation stage. At the same time as the inversion is increased the bottle is twisted so that the yeast falls to the neck of the bottle, from there it can be removed by disgorgement.

Residual Sugar: Any sugar left in the wine after the fermentation is complete and the yeast has died out. Sometimes residual sugar is desired, as in sweeter white wines or dessert wines. Residual sugar that is perceptible on the palate is seen as a defect in most red table wines.

Reverse Osmosis: An expensive and inconvenient commercial process through which alcohol and acetic acid can be removed from the wine so that it meets aesthetic or, more commonly, regulatory levels.

Secondary Fermentation: A bit of a misnomer, secondary fermentation can refer to two things: First, a true second fermentation that follows completion of the first. Usually purposely started by adding yeast and extra sugar to the finished wine to make CO2 for a sparkling wine effect. Second, it is the second stage of the primary fermentation whereas after a vigorous primary fermentation the wine is transferred to a carboy or barrel (secondary fermenter) to finish the last, protracted Secondary Fermentation when the yeast are slowing down and the wine needs to be protected from oxygen and any air-borne microbial contaminants.

Stopper aka Rubber Stopper or Bung: The rubber stopper is placed in the neck of a carboy or demijohn that reduces the size of the opening to accept an airlock and to create an airtight seal.

Stuck Fermentation: An undesirable condition where fermentation fails to begin or has stopped before all the sugar has been converted to alcohol and CO2.

Sulfites: A class of sulfur-containing compounds used in winemaking as an antimicrobial agent, as an antioxidant, and as a preservative and to kill off wild yeasts prior to fermentation of wine.

Sulfur Dioxide: In the form of potassium metabisulfite crystals, liquid sulfur dioxide, or sulfur dioxide gas, sulfur dioxide is an effective and safe preservative, antioxidant, and antimicrobial agent that has been used for millennia to facilitate the winemaking process. It is a respiratory irritant in high concentrations, so it should always be handled with care. Usual levels of free sulfur dioxide in table wines is about 20 to 40 parts per million.
Sweet wine: Any wine in which there is perceptible residual sugar. Sugar is perceptible, depending on the individual taster and the composition of the individual wine, at about 1.5 percent.

Sweet Reserve: A sample of the original juice from which a wine is made and saved to later be used to sweeten the finished wine after it has been fermented to dryness and the wine is stabilized. The sweet reserve is usually refrigerated or frozen until needed. Some advantages of using a sweet reserve to sweeten wine rather than sugar fresh flavor and natural aroma to the wine. It may also improve the color of the finished wine.

Tannin: The astringent phenolic anthocyanins found in grape skins, seeds, and stems that make your mouth pucker and feel dry when you drink red wine. Tannins are extracted from the grapes during the fermentation and maceration process. Tannins can also be extracted from oak and will also act as a natural preservative. Excessive tannins will leave a wine unbalanced and tasting bitter with a drying or puckering sensation in the mouth.

Tartaric Acid: The principal acid in wine made from wine grapes.

Tartrates: Harmless crystals of potassium bitartrate that may form in cask or bottle (often on the cork) from the tartaric acid naturally present in wine.

Titratable Acidity (TA): Sometimes called total acidity; the total amount of acids in a wine or must that is measured by titration of the wine or juice with a base such as sodium hydroxide. The amount of acid (expressed in grams of acid per liter of wine) will tell you roughly how acidic the wine is. Knowing this information will allow you to make any needed adjustments.

Topping Up or Topping Off: To add liquid back to a wine to minimize dead air space or head space in your aging vessel, carboy, barrel, etc. Topping up is usually done after racking to replace the volume that is lost by removing sediment and lees. Topping off prevents oxidation problems and can be done with another finished wine or glass marbles. Water will work but can dilute your wine lowering its alcohol level and reducing its acidity.

Viniculture: The science and art of growing wine grapes.

Viticulture: The science and art of growing grapes.

Wild Yeast: Sometimes referred to as "natural yeast," wild yeast are the yeast fungi that are naturally present on grapes, on winery equipment, and just in the air itself. Many wineries rely on these itinerant microorganisms to start their wine fermenting, but since these yeast strains are far from uniform in population they are not a dependable source to ferment your wine from and can be a serious risk. Wild yeast have been known to cause stuck fermentations, high hydrogen sulfide concentrations, and visual defects in finished wine, as well as a host of other spoilage problems.

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