autolysis: disintegration of yeast cell walls, which adds amino acids, enzymes, and lipids into the wine; produces secondary aromas and flavors
lees:
sur lie: "on the lees"; practice of allowing wine to rest on dead yeast cells to add secondary aromas and flavors
Typically 0.5% to 0.75% of volume
Six main types:
Acetic acid: not found in grapes but is a product of alcoholic fermentation from the bacteria acetobacter; a volatile component that adds to aromas at low amounts; produces a wine fault, volatile acidity, at high amounts
Citric acid: a very minor (often undetectable) component in grapes; sometimes added to wine to increase its total acidity
Lactic acid: not found in grapes but is a product of malolactic conversion from the bacterial family Oenococcus oeni; softer than malic acid, MLF produces a creamy texture and buttery aroma in some wines
Malic acid: a major component in grapes; sharp taste of green apples; levels drop as grapes ripen; more commonly found in ripe grapes in cooler climates than warmer ones; transformed into lactic acid during malolactic conversion
Succinic acid: a minor component in grapes and a product of alcoholic fermentation; has a sharp, slightly bitter, slightly salty flavor
Tartaric acid: the most prevalent acid in grapes; strongest in terms of pH; crystalizes at low temperatures, producing tartrates or "wine crystals," and does not redissolve into wine; can be avoided with cold stabilization techniques
Represents the chemical strength of the acids present in wine
Typically ranges between 2.9 and 3.9 on the pH scale
Considered a reliable measure of a wine's stability and assessed for potential addition of sulfites
Also known as titratable acidity
Represents the total volume of acids present in wine
A high TA may not equate to high acidity in flavor if the acids have a higher pH (like lactic, which is softer than malic)
Typically 10-15% of volume
Contributes body and weight to wine
Four main types:
Ethyl alcohol: also known as ethanol; primary result of alcoholic fermentation and main alcohol in wine; a volatile compound that allows aromas to rise from wine
Glycerol: third most abundant component in wine, usually around 1%; a product of alcoholic fermentation; more prevalent in botrytized wines; adds sucrosity, if not necessarily body or viscosity
Methyl alcohol: also known as methanol
Fusel alcohols: also known as fusel oils or higher alcohols
Also known as phenolics, polyphenolics, or polyphenols
Various molecules that, although limited in volume, have a major impact on wine
Concentrated primarily in grape skins, seeds, and stems
Over time, some phenolic compounds can polymerize, chaining together to such a degree that they precipitate from wine as sediment; after extreme aging, they can break down again
Five main types:
Anthocyanins: red, purple, and blue pigments that give red wines their color; affected by a wine's acidity; more acidic wines appear redder in hue, whereas less acidic wines appear bluer
Flavonols: also known as flavones; yellow pigments that give white wines their color; increase in volume as grapes are exposed to sunlight; sunnier climates produce more golden wines than cooler or cloudier climates
Resveratrol: a component that, although considered beneficial to health, has not been proven in many studies to have much salutary effect
Tannins: general group of astringent, bitter compounds; also found in oak barrels; add structure and aging ability to wine, given their ability to slow oxidation
Vanillin: aromatic compound derived from oak; same compound as found in vanilla
Grapes typically contain between 15 and 28% sugar at harvest
Two main types, both monosaccharides or simple sugars:
Fructose
Glucose
Residual sugars are those remaining in wine after fermentation, whether on the part of a winemaker's intervention or natural causes
Adds weight, viscosity, body, and texture to wines
Typically 80-90% of volume
On rare occasions, winemakers add water to dilute concentrated components
Four main types:
Aldehydes: oxidized alcohols formed when wine is exposed to air; most common form is acetaldehyde, or oxidized ethyl alcohol; sometimes a desirable and intentional product, as for Sherry or Madeira; can occur when wines are open too long or exposed to heat
Esters: combination of acid and alcohol molecules; largest group of odor-producing compounds in wine; most common form is ethyl acetate, a combination of ethyl alcohol and acetic acid, which produces fruity and floral aromas in low concentrations and faulty aromas of nail polish remover at high amounts
Gases: most common dissolved gas in wine is oxygen; sulfur often added to wine to absorb oxygen; carbon dioxide also common, both in still wines (which provides pétillance) and as the main textural component of sparkling wines
Sulfites: group of chemicals composed of sulfur; natural product of fermentation; often added as preservative and antibacterial agent