Wine Production



ACETALDEHYDE. Product of the oxidation of ethyl alcohol; at low concentrations enhancing wine aromas, but at high concentrations giving a "Sherry-like smell."

ACETIC ACID. All wines contain acetic acid, the active ingredient in vinegar, but usually the amount is quite small - from 0.03 percent to 0.06 percent - and not perceptible to smell or taste. Once table wines reach 0.07 percent or above, a sweet-sour vinegary smell and taste becomes evident. At low levels, acetic acid can enhance the character of a wine, but at higher levels (over 0.1 percent), it can become the dominant flavor and is considered a major flaw.

ACETIFICATION. The oxidative conversion of wine to vinegar, ethanol to acetic acid. An aerobic fermentation by Acetobacter.

ACETOBACTER. Genus of bacteria of the family Bacteriaceae. The organisms oxidize alcohol to acetic acid.

ACIDIFICATION. The addition of acid to wine by a winemaker. The goal is to balance the wine's soft components (sugar, alcohol and fruit). It is legal in some areas - such as Bordeaux, Burgundy, Australia and California - to correct deficient acidity by adding acid.

ACIDITY. The quality of wine that gives it its crispiness and vitality. The three main acids found in wine are tartaric acid, malic acid, and lactic acid. The first two come from the grapes and the third from malolactic fermentation which often occurs in the winemaking process.

ACIDS. Essential components of grapes and wine, giving freshness and bite. Tartaric and malic acid comprise 69 to 92 percent of the organic acid of grapes. Citric, lactic, succinic and acetic acids are also present. Malic acid is naturally converted to the softer (yogurty) lactic acid via malolactic fermentation, which naturally tends to follow the alcoholic fermentation.

AEROBIC. Requiring the presence of oxygen. In aerobic exercises, the muscles are never deprived of oxygen.

AGING. The general time-related improvement of wines specifically after bottling, but sometimes applied to the whole period of wine storage after fermentation. (See also Maturation.)

ALBUMIN. A water-soluble protein found in egg whites etc. Coagulates with heat. Used for fining.

ALCOHOL. The product of fermentation created by the enzymes in yeasts working on sugar. Alcohol is also added in neutral form during or after fermentation to produce fortified wines. Usually measured as percentage by volume [alcohol by volume (abv)]. See Ethanol.

ALCOHOL BY VOLUME (abv). The measure of the alcohol (ethanol) content contained in a given volume of alcoholic beverage and expressed as volume percent.

ALDEHYDE. A substance with the -OHO group, typified by acetaldehyde, a strong-smelling compound produced during the oxidation of wine.

AMELIORATION. A specific meaning in winemaking applies especially to must betterment, particularly from fruits other than wine grapes. It involves lowering of excessive acid, usually by dilution with water, and increasing the sugar content so that palatable and stable wines result.

ANTHOCYANINS. A group of polyphenols, found in the skins of red grapes, (and many other fruits and flowers) that is mainly responsible for the color of red wines.

ANTIOXIDANT. A substance that minimizes the effect of oxidation.

ARCHIMEDES SCREW. A broad-threaded screw encased in a tube.

AROMA. The odors in wines related to the grape from which they were made as distinguished from process and aging odors. (See also Bouquet.)

ANTIOXIDANT. A substance that minimizes the effect of oxidation.

ASSEMBLAGE. French term for the blending of different vats and parcels of wine to make up the final blend.

ASTRINGENT. A tactile sensation, mostly when tasting red wines that can be described as dry, sour, mouth puckering. Phenolics found in the skins and seeds of grapes are the cause of the sensation. Astringency is usually attributed to high tannin levels found in some red wines (and a few whites).

ATMOSPHERE. The mass of air surrounding the earth, consisting approximately of 78 percent nitrogen and 21 percent oxygen. Also, a unit of pressure of 14.7 pounds per square inch, or 760 mm of mercury.

AUTOLYSIS. Interaction between wine and solid yeast matter resulting in a distinctive bread- or biscuit-like flavor. Autolytic character is encouraged by ageing a wine on the lees, as takes place in the bottle during producer maturation of Champagnes, or in vat or barrel for certain other white wines. See also Yeast autolysis.