Acid - Essential component - in malic (appley) and tartaric form - of wine, giving freshness and bite. Malic acid is naturally converted to the softer (yoghurty) lactic acid via malolactic fermentation, which naturally tends to follow the alcoholic fermentation which has turned the sugar into alcohol. Tartaric acid is often added in warm regions.
Alcohol - The by-product of fermentation, created by yeasts working on sugar. It is also added in neutral form during or after fermentation to produce fortified wines. Measured as a percentage of volume.
Anthyocyanin - Grape-skin tannin responsible for colour and flavour in red wines.
Autolysis - Interaction between wine and solid yeast matter giving a distinctive flavour, encouraged by ageing wine on its less in Muscadet and Champagne.
Barrel-ageing - Fermented in barrel in order to intensify oak and vanilla flavours.
Barrique - The traditional Bordelais oak barrel, now widely adopted elsewhere, with a capacity of 225 litres (50 gallons). Term used by Italian wine-makers to indicate the use of new oak barrels.
Bentonite - Clay used for fining.
Blending - The mixing of several wines to create a balanced cuvee. Also called assemblage.
Cap - The floating skins in a red wine must.
Capsule - Once lead, now foil or plastic-film which coveres and protects cork and bottle neck. Wax is also sometimes used - particularly for vintage port.
Carbon dioxide (CO2) - By-product of fermentation, trapped in wine as bubbles by sparkling wine-makers using the Champagne method, and otherwise induced in or injected into all sparkling wines.
Carbonic maceration - Uncrushed grapes ferment under a blanket of CO2, intensifying fruit flavours. Also known as "whole-berry fermentation".
Centrifuge - Machine used to separate wine from the less after fermentation. Also used in production of low-alcohol wines.
Concentrated grape must - Grape juice that has been reduced by heating to 20 per cent of its volume. If "rectified", it has also had its acidity neutralized. An alternative to using sugar in chaptalization.
Congeners - The colouring and flavouring matter in wines.
Cool fermentation - Temperatures are kept below 18oC (64oF).
Crushing - The gentle breaking of berries before fermentation.
Cryoextraction - A recently developed technique which involves partially freezing grapes before crushing them in order to separate the sweet, flavoursome juice from the water (which freezes more easily). Used in rainy vintages.
Cuvaison - Period of time a red wine spends in contact with its skins.
Cuve - A vat traditionally made of wood used for storage or fermentation.
Cuvee - A specific blend.
Debourbage - Period during which the sediments drop to the bottom of the tank allowing them to be separated from the fresh must.
Egrappoir - Machine which removes stalks from grapes before they are crushed.
Elevage - The "rearing" or maturing of wines before bottling.
Fermentation - The conversion of sugars into alcohol through the action of yeasts.
Filtration - Passing the wine through a medium to remove bacteria and solids (and possibly flavour - which is why some producers prefer not to filter).
Fining - The clarification of must or wine, usually using natural agents such as egg white, gelatine, isinglass or bentonite which, as they sink, attract and drag down impurities (and possibly desirable flavours) with them.
Fortification - The addition of alcohol to certain wines (e.g. sherry and port) either before or after fermentation is complete.
Free-run juice - The clear juice which runs from the crushed grapes before they are pressed. The best-quality juice.
Hectolitre - 100 litres.
Isinglass - Fining agent derived from fish.
Lees - Dead yeasts left after fermentation.
Maceration - Period of contact between wine and skins in red wines.
Maderization - Term for heat-induced oxidation, e.g. in Madeira.
Made wine - Wine made from concentrated must - not fresh grapes.
Malolactic fermentation - Natural or induced conversion of malic acid to the softer lactic acid.
Marc - Skins, stalks and pips left after pressing. May be distilled into brandy.
Methode champenoise - Now-defunct term replaced by methode classique.
Methode classique - The method used in Champagne of inducing of secondary fermentation within the bottle in which the wine is sold.
Must - Unfermented grape juice.
Must concentrators - Ingenious machines used to remove water from the juice of grapes picked in the rain.
Must weight - Amount of sugar in the must.
Mutage - The addition of alcohol to stop fermentation - used to make sweet fortified wines.
Oak - Preferred type of wood in which to mature wine. Provides character and imparts flavour. Also used in chip form.
Oenology - The science of wine-making.
Oxidation - Result of air contact with wine. Controlled in the maturation process; destructive in excess.
Pasteurization - Sterilizing (usually cheap) wine by heating.
PH (number) - Measure of acidity (low) or alkalinity (high).
Press - Machine used gently to squeeze out juice remaining in skins.
Press wine - Blending wine obtained by pressing the grape skins after maceration.
Pumping over - The process of pumping the must over the floating cap of skins to obtain more colour and flavour.
Racking - Decanting from one vessel to another leaving the less behind.
Sugar - The sugar in fresh grape juice is measured prior to fermentation as this will determine the alcohol content and style of wine. Scales of sugar measurement are: in France, Baume; in the New World, Brix; in Germany, Oechsle. In some regions, sugar may be added to chaptalize the must - to raise its potential alcoholic strength, but not to sweeten it.
Sulphur dioxide (SO2) - Invaluable antiseptic, antioxidant and preservative. Used sparingly by wise wine-makers.
Sussreserve - In Germany, England and a few other regions, wines can be sweetened by the addition - back-blending - of sweet, unfermented grape juice.
Tannins - Extracts from red grape skins and oak which give a red wine backbone. The mouth-drying quality of cold black teas is due to tannin.
Tartrates - Potassium bitartrate is naturally present in all wine. Most is removed before bottling but some may linger in the form of harmless tartrate crystals.
Ullage - The air space between the wine and roof of cask or, in bottle, cork.
Varietal - Wine made and named after one or more grape varieties.
Yeast - Naturally present on grapes, or added in cultured form, this is what makes grape juice ferment.