acetic acid: is the most volatile of the primary acids associated with wine and is responsible for the sour taste of vinegar. During fermentation, activity by yeast cells naturally produce a small amount of acetic acid. If the wine is exposed to oxygen, acetobacter bacteria will convert the ethanol alcohol into acetic acid.
acid: is an important component in winemaking and the finished wine product itself. It influences the color, balance and taste of the wine and protects it from bacteria. There are three primary acids in wine grapes - tartaric, malic and citric.
acidity: in wine tasting refers to the fresh, tart and sour attributes of the wine which is evaluated in relation to how well the acidity balances out the sweetness and bitter components of the wine.
air lock: is a device, containing water, which allows the carbon dioxide to escape without oxygen entering during fermentation.
alcohol: is any organic compound in which a hydroxyl functional group (-OH) is bound to a carbon atom, usually connected to other carbon or hydrogen atoms. The general formula for which is CnH2n+1OH of which ethanol (C2H5OH) is the type of alcohol found in wine. The word alcohol refers specifically to ethanol.
alcohol by volume (ABV): is a standard measure of how much alcohol (ethanol) is contained in wine (expressed as a percentage of total volume).
Allier: barrels are made from oak from the Tronçais forest, and is one of the most favoured woods for aging red wines in. Other primary forests each with slightly different wood characteristics are Nevers, Limousin and Vosges.
anthocyans: are water soluble pigments that may appear red, purple or blue depending on the pH. They belong to a class of molecules called flavonoids, and have little taste (a moderate astringency) or smell.
antioxidant: a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions that damage cells. Red wine is a good source of antioxidants.
ascorbic acid: also known as vitamin C, is found in young wine grapes prior to veraison but is rapidly lost throughout the ripening process. In winemaking it is used with sulfur dioxide as an anti-oxidant to prevent oxidation, often added during the bottling process for white wines.
Baumé: scale is used in winemaking for the measurement of density of liquids.
botrytis cinerea: The fungus that attacks the grape skins under specific climatic conditions (usually alternating periods of moisture and sunny weather). It causes the grape to become super concentrated because it causes a natural dehydration. Botrytis cinerea is essential for the great sweet white wines of Barsac and Sauternes. It rarely occurs in the Rhône Valley because of the dry, constant sunshine and gusty winds.
Brix: (symbol °Bx) is a unit representative of the sugar content of an aqueous solution. The °Bx has traditionally been used in the wine, sugar, fruit juice, honey and other industries.
butyric acid: is a bacteria-induced wine fault that can cause a wine to smell of spoiled Camembert or rancid butter.
carbonic maceration: is a winemaking technique, often associated with the French wine region of Beaujolais, in which whole grapes are fermented in a carbon dioxide rich environment prior to crushing.
carbon dioxide (CO2): in the form of dry ice is often used in the wine making process to cool down bunches of grapes quickly after picking to help prevent spontaneous fermentation by wild yeasts. It is also used to top up wine bottles or other storage vessels such as barrels to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gasses such as nitrogen or argon are preferred for this process by professional winemakers.
citric acid: is found in minute quantities in wine grapes. The citric acid most commonly found in wine are commercially produced acid supplements derived from fermenting solutions.
cold stabilization: is the clarification and stabilization of wine in winemaking which involves removing insoluble and suspended materials that may cause a wine to become cloudy, from unwanted sediment deposit or tartrate crystals.
diacetyl: is a natural byproduct of fermentation, which occurs in alcoholic beverages giving them a buttery flavor.
diammonium phosphate: is a yeast nutrient which contains nitrogen and phosphorous. It is the basic nitrogen source in nearly all wine yeast nutrients, and can be used on its own or to supplement prepared nutrients.
ethanol: is also called pure alcohol. It is a volatile, flammable and colorless liquid. The fermentation of sugar into ethanol is one of the earliest organic reactions employed by humanity whilst the intoxicating effects of ethanol consumption have been known since ancient times.
fermentation: The process of fermentation is a function that turns grape juice into an alcoholic drink. Yeast interacts with sugars in the juice to create ethanol, commonly known as ethyl alcohol, and carbon dioxide (as a by-product).
flying winemaker: A winemaker who travels extensively across the globe, sharing techniques and technology from one region of the world to another. The term originated with Australian winemakers who would fly to Northern Hemisphere wine regions in Europe and the United States during the August-October harvest time when viticulture in the Southern Hemisphere is relatively quiet.
hydrogen sulphide (H2S): is a colorless, very poisonous, flammable gas with the characteristic bad odor of rotten eggs. It's generally thought to be a metabolic by-product of yeast fermentation in nitrogen limited environments.
isoamyl acetate: is an organic compound formed from isoamyl alcohol and acetic acid. It has a very strong odor. reminiscent of pear drops and banana. Isoamyl acetate is used to confer banana flavor in foods.
lactic acid: is a much milder acid than tartaric and malic, and is often associated with “milky” flavors in wine. It is produced during winemaking by lactic acid bacteria (known as LAB) which includes three genera: Oenococcus, Pediococcus and Lactobacillus.
lees: refers to deposits of dead yeast cells and other particles that precipitate, or are carried by the action of "fining", to the bottom of a vat of wine after fermentation and aging.
Limousin: is the region in central France where the Limousin oak barrels originate from. Other primary forests each with slightly different wood characteristics are Allier, Nevers, Tronçais and Vosges.
maceration: is the process by which the red wine receives its red color during the winemaking process where tannins and color agents are leached from the grape skins and stems into the must.
malic acid: along with tartaric acid, is one of the principal organic acids found in wine grapes. Found in nearly every fruit and berry plant but it's most often associated with green apples from which flavor it most readily projects in wine. Its name comes from the Latin malum meaning “apple”. Malic acid can be further reduced during the winemaking process through malolactic fermentation or MLF.
malolactic fermentation: normally occurs after the primary fermentation has completed, when the grape sugars have been converted by yeast, into alcohol and carbon dioxide (CO2). Lactic acid bacteria, Oenococcus oeni, and some other species of Lactobacillus and Pediococcus are responsible for this conversion.
must: is freshly pressed grape juice that contains the skins, seeds, and stems of the fruit. The solid part of the must is called pomace. Making must is the first step in winemaking.
Nevers: is the location within the Burgundy region in France where the Nevers oak barrels originate from. Other primary forests each with slightly different wood characteristics are Allier, Limousin, Tronçais and Vosges.
noble rot: is a form of grey fungus botrytis cinerea that affects wine grapes. If it develops because of wet weather, it can become 'grey rot', so destroying entire grape crops. However, in well ripened grapes, this rot is beneficial, as the infestation causes the berries to partially dry out, resulting in a concentration of sweetness. This wine will be termed 'botrytized'.
oenology: is the science and study of all aspects of wine and winemaking except vine-growing and grape-harvesting, which is a subfield called viticulture.
oeschle: is a hydrometer scale measuring the density of grape must, which is an indication of grape ripeness and sugar content used in winemaking.
oak: plays a significant role in winemaking and can have a profound effect on the resulting wine, affecting the color, flavor, tannin profile and texture of the wine. Oak can come into contact with wine in the form of a barrel during the fermentation or aging periods.
oxidation: occurs when a wine is in contact with oxygen. The wine turns a brownish color. Oxidation can occur throughout the winemaking process, and even after the wine has been bottled.
pH: is a measure of the acidity of an aqueous solution such as wine. The lower the pH, the higher the acidity.
pomace: is the solid remains of grapes, after pressing the juice out. It contains the skins, pulp, seeds, and stems of the fruit. Oenocyanin, a natural red dye and food-coloring agent, is produced from grape pomace.
potassium bitartrate: is formed in wine, through the reaction between the bitartrate ion from tartaric acid, and the potassium ion found in grapes, especially grape skins.
racking: is a term describing the removal of a liquid, the wine, from its sediment, the lees. Post fermentation wines will be racked to begin the clarification and hygiene process.
refractometer: is an analog instrument for measuring a liquid's refractive index. This device will determine how much natural sugar is in the sample of grape juice.
residual sugar: is the amount of sugar remaining in the wine and usually measured in grams of sugar per litre of wine, often abbreviated to g/l. Even among the driest wines, it is rare to find wines with a level of less than 1 g/l.
sorbic acid: is a winemaking additive used often in sweet wines as a preservative against fungi, bacteria and yeast growth. Unlike sulfur dioxide, it does not hinder the growth of the lactic acid bacteria.
specific gravity (SG): in the context of fermenting alcoholic beverages, refers to the specific gravity, or relative density compared to water, of the must at various stages in the fermentation. SG is measured using a hydrometer.
stuck fermentation: occurs in winemaking when the yeast become dormant before the fermentation has completed. Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation (such as in the production of fortified wines), a stuck fermentation is an unintentional and unwanted occurrence that can lead to the wine being spoiled by bacteria and oxidation.
sulfur dioxide: is a common wine additive, used for its antioxidant and preservative properties. The overdosing of a wine will leave a perception reminiscent of matchsticks or burnt rubber.
tannin: is an astringent, bitter polyphenolic compound. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine.
tartrates: are salts of tartaric acid which can settle out in a wine forming crystals. They are completely harmless but can be considered unsightly.
tartaric acid: in winemaking is the most important acid in wine due to its role in maintaining the chemical stability of the wine and its color and finally in influencing the taste of the finished wine. Along with malic acid, and to a lesser extent citric acid, tartaric is one of the fixed acids found in wine grapes.
thiamin hydrochloride: is a yeast nutrient to facilitate the growth of micro-organisms which in turn aids the fermentation of wine. It is vitamin B-1 and is typically vegan and synthetic.
Tronçais: is a French national forest, comprising 10,600 hectares in the Allier region. Its oaks, planted by the minister of Louis XIV to supply the French navy, constitute one of the principal stands of oaks in Europe. Other primary forests each with slightly different wood characteristics for wine are Allier, Nevers, Limousin and Vosges.
volatile acidity (VA): on vinegar taint is caused by acetic acid bacteria. This can be from either a by-product of fermentation, or due to the spoilage of finished wine.
Vosges: is the location in north eastern France where the Vosges oak barrels originate from. Other primary forests each with slightly different wood characteristics are Allier, Nevers, Limousin and Tronçais.
woody: When a wine is overly oaky it is often said to be woody. Oakiness in a wine's bouquet and taste is good up to a point. Once past that point, the wine is woody and its fruity qualities are masked by excessive oak aging.
yeast: is used in winemaking where it converts the sugars in grape juice or must into alcohol and carbon dioxide. This reaction causes a fermentation. Yeast is normally present on the grapes; however, most winemakers like to introduce a known yeast culture to give a typical character to a wine. Most added wine yeasts are strains of Saccharomyces cerevisiae. The growth of some yeasts such as Zygosaccharomyces and Brettanomyces in wine can result in wine faults and subsequent spoilage.