by Graeme Leith
Drosophila The vinegar fly, or Drosophila, presents a challenge to the winemaker because of its habit of feeding on rotting fruit and subsequently transporting vinegar bacteria into the winery. If good housekeeping is observed, they should not become a problem, but if wine or fruit detritus is left about, they can breed at an astonishing rate due to their average egg-hatching time of 24 hours.
Erinose See Blister mite
Eutypa disease A fungal disease that attacks the woody parts of a vine. Sometimes called dead arm, it can be very destructive.
Ferment The process by which grape juice is turned into wine. Either introduced or naturally occurring yeasts cause the sugars in the must to convert to heat, carbon dioxide and alcohol.
Fining Fining has been practised since early Roman times but it is only fairly recently that its workings have been understood. There are two forms of fining. The most common is the clarification of wine by an agent that causes precipitation (physical fining). The other is purification by use of an agent (chemical fining). Egg whites, blood, casein, bentonite, gelatin, isinglass and milk are all traditional fining agents that are still used today to clarify or purify wine, and increase its organoleptical properties (or, in other words, remove unpleasant properties from the wine).
Foot-stomp A traditional means of crushing grapes by treading with bare feet, considered to be the gentlest means of crushing.
Grappa A spirit distilled from fermented grape material, especially marc, the solid residue of a ferment.
H2S Hydrogen sulphide, a by-product of fermentation. Excessive amounts can cause wine spoilage.
Isinglass A gelatinous material made from the swim bladder of fish, especially the sturgeon. It is used for clarifying wines, especially white wines.
Lees Sedimentary matter that collects at the bottom of a vessel after fermentation or maturation. Wine is usually drawn off the lees, but in some cases may remain and be periodically stirred through the maturing wine.
Malo-lactic fermentation Malic acid is a natural acid of grapes and is quite sharp. Most wines benefit from the ‘malo’, as the bacterial action that occurs changes the malic acid into the softer lactic acid. If the desirable bacteria does not exist in the winery, or a different strain is desired, the winemaker can purchase the desired strain, either frozen or dried, and introduce it to the wine.
Marc Marc is the residue or by-product of the production of wine, comprising the leftover pips and skins.
Mouthfeel When all the components of a wine are in good balance the wine should feel good in the mouth.
Muscadet One of France’s dry white commercial wines, muscadet can be very ordinary, but at its best compliments sea food, particularly that of the North Atlantic coast, very well.
Must The crushed grapes in the winemaking process.
Nose The smell, or bouquet of a wine.
pH values This is the measure of the active acidity/alkalinity of a wine, as opposed to the total acidity of the wine. The optimum range for ferments is between 3.1 and 3.4. The lower the pH value, the more acidic the wine.
Phylloxera A parasitic aphid on the roots of vines that in many cases causes the death of the vine. At the turn of the century a phylloxera outbreak devastated European vineyards, and the vines had to be grafted onto American rootstocks. Some phylloxera still exists in parts of Australia and many vineyards use grafted rootlings.
Rootlings Vine cuttings that have sprouted roots, usually planted out into the field as one-year-old dormant vines.
Spacings These vary tremendously. Depending on the whim of the grower, they can be as close as 1 metre by 1 metre or as far apart as you like. For practical purposes spacings of, say, 3 metres by 2 metres make sense.
Veraison This occurs when the berries begin to accumulate sugars and the colour of the pinot berries changes from green to red.
Vintage Winemaking, or vinification, is the production of wine, starting with ‘vintage’, the selection and harvesting of wine grapes, and ending with bottling the finished wine.
Volatile acids The main volatile acids are acetic acid and ethyl acetate. Small amounts of acetic acid are formed during alcoholic fermentation and are not deleterious, but careless handling can result in unacceptable amounts being produced, with consequent spoilage.
Yeast cells Yeast is a unicellular fungus and one of the lowest forms of life. The cells are tiny (7 to 8 microns) and they reproduce by budding. It is estimated that there are about 500 million cells in 250 millilitres of an active ferment.