Winemaking Dictionary

Winemaking Dictionary


Explore the nuanced world of wine with our Winemaking Dictionary, designed to explain some of the finer points of the process that turns grapes into wine. Learn the ABC’s of winemaking as described by our team of experts.

Appellation: the fruit provenance of a certified wine. Many old world appellations regulate parameters like the varieties used, minimum aging time, percentage of blending allowed, vineyard yield, and possibly winemaking techniques. This legal classification protects both the consumer from purchasing a counterfeited product and the winemaking tradition and culture of a specific place. In the U.S., and many in the New World, appellations tend to denote geographical boundaries.

Barrel Fermentation: the primary fermentation of wine that takes place in the barrel. This technique can impart buttery, nutty, and oak flavors.

Bentonite: a fining clay used to remove proteins which can cause haze in wine. Bentonite has a negative charge that attracts positively-charged solids suspended in the wine, causing the solids to fall out of solution and sink to the bottom of the holding vessel.

Botrytis: a fungus that infects wine grapes. Affectionately referred to as “noble rot,” this fungus feeds off of water within the grapes, and in turn produces a high concentration of sugar, ideal for making sweet dessert-style wines. However, botrytis also takes the form of bunch rot in wetter conditions. When this occurs, the cluster must be discarded.

Brettanomyces: considered by many (but not all) to be a spoilage yeast, identified by its characteristic band-aid or horse stable scent. While some wines benefit from low levels of brettanomyces, which can add complexity, its presence is generally considered a wine fault.

Brix: a unit of measurement used to determine the sugar content in a wine solution.

Canopy Management: vineyard management technique aiming to control the productivity of the vine’s canopy including: choice of trellis, pruning, shoot trimming, positioning, thinning, and green harvesting.

Carbonic Maceration: a technique in which grapes are whole-cluster fermented in a sealed, carbon dioxide rich environment. The carbon dioxide gas permeates the grape skin, initiating fermentation on a cellular level within the intact individual grapes. The resulting wine is often light, fruity, and soft.

Chaptalization: the process of adding sugar to grape juice prior to fermentation. This increases the potential alcohol percentage of the finished wine by providing the yeast with more sugar to ferment. It is not intended to make the wine sweet.

Clone: a grape vine variety with an exact match to that of its parentage. It can be copied from the clippings of a “parent” plant. This clipping can either be planted or grafted onto an existing rootstock. Clones are selected for many reasons including: resistance to disease, flavor profile, cluster size, fruit maturation rate, and fruit yield.

Cold Stabilization: the process used to reduce or remove tartrate crystals from the wine to prevent sediment from appearing in white wine once it has been bottled. This is achieved by dropping the temperature of the wine to near freezing for at least 2-3 weeks. This causes the tartrate crystals to stick to the walls of the tank or holding vessel, and the wine can then be racked to another vessel, leaving the tartrate crystals behind.

Destemming: the separation of grapes from their stems, usually achieved by a mechanical destemmer. Within the destemmer, the clusters pass through a perforated cylinder where the grapes are gently paddled off the stems, and the discarded stems are ejected out the back of the cylinder.

Extended Maceration: the extended soaking of the juice in contact with the skins and seeds that occurs after primary fermentation is completed. This technique is used to maximize extraction and often creates a richer, more full-bodied wine with even greater aging potential.

Filtration: the pumping of wine through a filtration medium to ensure a clear and stable finished wine. It is an important tool in ensuring the wine is free from particulate matter and any microbial bacteria that could adversely affect the taste or appearance of the wine.

Fortification: the adding of a neutral spirit (in most case derived from grapes) to a fully or partially fermented must. Historically, this process was used to protect wine from spoilage during transportation, in times when temperature controlled containers were not yet available.

Lees: dead yeast cells and other sediment particles that have settled to the bottom of the fermentation or aging vessel. Most often, the lees are left behind when the wine is racked to another vessel as part of the fining process. On occasion, the wine is left on the lees and periodically stirred. This technique, called sur lie, imparts flavors and builds up the palate of the wine.

Malolactic (Secondary) Fermentation: the conversion of naturally occurring malic acid into lactic acid via lactic acid bacteria. Most red wines go through complete malolactic fermentation to reduce the total acidity of the wine. White wines vary in their use of this process, contingent upon the winemakers stylistic choices.

Must: describes wine in its earliest stages, as a collection of juice, grape skins, seeds, and occasionally stems.

Nutrients: compounds used to replenish and invigorate yeast cells. Nutrients can be added in the early stages of the fermentation process to strengthen the yeast colony.

Oak Treatment: the use of oak barrels as aging vessels to affect the tannins, texture, and flavor profile of wine. Oak from different regions each have their own distinct characteristics. American oak often imparts notes of dill and coconut. French oak can add vanilla, caramel, and butterscotch. Hungarian oak often produces cocoa or nutty aromas.

Oxidize: one of the most common wine faults, that can occur at any stage of the winemaking process, including after the wine is bottled. Oxidation occurs when the wine is exposed to too much oxygen, causing loss of color, aroma, and flavor. Inert gases such as argon or nitrogen used in conjunction with SO2 help to guard against oxidation, as does keeping barrels topped up.

Oxygen Management: the close monitoring of oxygen levels throughout every stage of the winemaking process. The absence of oxygen protects the delicate aromatics and color of white wines aged in stainless steel tanks, whereas the slow oxidation over an extended period of time adds depth and complexity to red wines aged in oak barrels.

pH (Potential of Hydrogen): a numeric scale used to specify the acidity or basicity of a solution, and in winemaking determine fruit ripeness. Low pH wines are generally bright and crisp, whereas high pH wines can taste flabby or flat. pH is also important in the overall stability and health of the wine. Wines with a lower pH (3.2 – 3.75) have a better defense against most types of bacteria, unlike high pH wines (4.0 – above) which are more susceptible to spoilage.

Phenolic Maturity: occurs during ripening of red and white varietals. It is identified by the maturity of all the components of the grape skin that contribute to the character of the final product. Phenolic maturity also applies to other polyphenolic components, such as the tannins in the skins and seeds of the berries.

Pomace: scrap material composed of grape skins, seeds, and other solids that remain after pressing. Pomace can be used for brandy production, grape seed oil, or return to the vineyard as fertilizer.

Primary Fermentation: also known as alcoholic fermentation, begins with the activation of yeast cells in the must. The yeast itself is naturally present in the grapes, but a cultivated strain can be added to the must. This allows the winemaker to better control variables such as fermentation rate and temperature. Once added, the yeast multiplies and begins to convert the sugar present in the grapes, creating energy and producing alcohol and carbon dioxide as a by-product. Once all the sugar has been converted into alcohol, the fermentation is complete and the wine is considered “dry.”

Pressing: the process by which juice is extracted from whole cluster grapes or must. This is done with the aid of a wine press, a bladder press, basket press, or even foot treading can be used to extract the juice from the grape skins. White wines are typically whole cluster pressed immediately after harvesting. Red wines are most often pressed following completion of primary fermentation.

Pump Over: the process of re-integrating the “cap” into the fermenting grape juice with the assistance of a mechanical pump to ensure optimal extraction and keep the cap from drying out. During the fermentation process, carbon dioxide causes the grape skins to rise to the top of the fermentation vessel, forming a cap. Since the skins are the source of color and tannins, they must be re-incorporated into the free run juice several times a day to achieve the desired level of extraction. This method is used when the fermentation is taking place in a larger vessel, and the pump re-introduces the grape skins to juice below.

Punch Down: the process of submerging the “cap” into the fermenting grape juice, with the aid of a punch down tool, as opposed to a mechanical pump.

Racking: the movement of wine from one vessel to another using either a pump or gravity to transfer the wine as gently as possible. Dependent upon the grape varietal the amount of times a wine is racked can vary greatly. Racking aids in the fining process by leaving behind any sediment that has accumulated in the aging vessel.

Residual Sugar (RS): the remaining grape sugars at the end of primary fermentation.

Rootstock: the vine’s root system located beneath the soil. Rootstocks contribute to the vine’s vigor, fruitfulness, and resistance to drought and disease but often do not influence the variety of grapes produced. Most grapevines are grafted onto a rootstock bred to be tolerant to pests or soil conditions specific to the growing region, similar to fruit trees.

Small Picking Lug: harvest grape container, usually made of plastic, with a capacity of roughly 36lbs, designed to give proper aeration to the fruit and to be stacked without damaging the grape clusters.

Sugar Accumulation: a feature of the ripening process involving the movement of sucrose from the leaves to the berries. Sucrose is a product of photosynthesis, and once in the berries, is separated into fructose and glucose through enzymatic activity.

SO2 (Sulfur Dioxide): a chemical compound used primarily as a preservative to guard against oxidation and any microbial bacteria that could spoil the wine. It is an important agent in stabilizing wine during the aging process and aids in extending the life of the bottled wine.

T-bin: a food-grade plastic open-top fermentation vessel used for individual small batch wines that holds up to 1,500 pounds (the equivalent of 2 barrels) of grapes or fermenting must.

TA (Titratable Acidity): the measure of acid present in a finished wine.

Tannins:  a naturally occurring compound that exists in the skins, seeds, and stems of a grape cluster and can be identified most simply as the drying sensation felt in the mouth when drinking wine. They are also present in the oak barrels used to age wine. Tannins act as a natural preservative essential to the longevity of many wines while also adding complexity and structure.

Terroir: the distinct characteristics of a region that influence the flavor of the wine. Everything from soil content, elevation, average temperature, rainfall, and hours of sunlight make up the distinct terroir of a vineyard.

Topping: adding more wine to barrels to remove “head space.” During the aging process, wine kept in oak barrels or other semi-permeable vessels evaporates over time, creating what is called head space. While a small amount of oxygen can be beneficial, too much can result in oxidation and lead to various wine faults. Topping the barrels minimizes the oxygen in contact with the wine.

Trellis: an artificial support that alleviates the weight of the vine canopy and aids the growing process. A complex trellis can be used for vines with high vigor and high vegetative growth to provide maximum sun exposure and proper ventilation of the leaves. Good amounts of sunlight improve the quality of the fruit, and appropriate ventilation will prevent rot and mold. Simpler trellis systems are more adequate for vines with low vigor.

VA (Volatile Acidity): indicates the presence of acetic acid produced either as a bi-product of fermentation or spoilage bacteria in the wine. High concentrations of acetic acid (1.2 grams per liter and above) can result in unpleasant vinegar-like qualities in wine.

Veraison: the point in the grape growing cycle when berries begin to change color and the skins begin to soften.  During veraison the grapes increase in weight and sugar content as the level of acidity begins to decrease. For winemakers and growers alike, the onset of veraison signals that harvest season is about to begin.

Yeast: the single cell microorganism responsible for fermentation in alcoholic beverages by converting the sugar in the must into ethanol. In winemaking, strands of the saccharomyces cerevisiae family of yeast are used almost exclusively. Yeast strains are selected based on different fermentative properties, such as temperature and alcohol tolerance, and rate of fermentation which directly impact the flavor profile of the finished wine.