Sometimes chemical herbicides are used for weeding; if they are applied to the whole vineyard, this is usually done at the end of winter and all ploughing is halted. This is known as “non-cultivation” and represents a considerable saving. However, some environmentally aware producers prefer not to weed the rows, as the weeds act to limit the growth of the vines naturally.
During the growing cycle, several different procedures are employed to limit excessive growth: epamprage, thinning out selected branches; rognage, trimming the tips; effeuillage, the removal of leaves, which allows the grapes to be more exposed to the sun; and accolage, training the shoots along wire espaliers. The wine-grower also has to protect the vines from disease, and to help him the Service for the Protection of Plants distributes information about various treatments, mainly sprays made from either natural or chemical products.
Finally, in autumn, after the harvest, the earth is heaped up around the vines to protect them from the winter frosts; a furrow in the middle of the row allows rain water to run away, and fertilizer is sometimes dug in here as well.
GRAPES AND THE HARVEST
The degree of maturity of the grape is an essential factor in the quality of the wine. But even within the same region climatic conditions vary from one year to the next, leading to differences in the composition of the grapes, which in turn determines the characteristics of each vintage. Hot, dry weather is generally needed for the grapes to fully ripen, and the date to start picking must be fixed with great care, taking into account both the ripeness and the health of the grapes.
Increasingly, manual harvesting is giving way to mechanical picking. The machines, fitted with “beaters”, knock the grapes on to a conveyor belt, and a fan is used to remove most of the leaves. The shock effect on the grapes detracts somewhat from their quality, especially where white grapes are concerned; the most reputable crus will be the last ones to use this form of grape-picking, despite the considerable progress that has been made in the design and construction of the machines. When the grapes are overripe at harvest-time, the level of acidity can be increased by adding tartaric acid, and if the grapes are underripe the acidity can be decreased by adding calcium carbonate. A wine that is not rich enough may not have a sufficiently high alcohol content and can be improved by adding concentrated must. Finally, in certain well-defined conditions, legislation allows for the adding of sugar to the must - this is known as “chaptalization”.
THE MAKING OF WINE
Wine is defined as “the product obtained exclusively from partial or total alcoholic fermentation of grape must or fresh grapes, which can be pressed or whole”.
All legal definitions require wine to have a minimum alcohol content of 8.5% vol or 9.5% vol, depending on the wine-growing area. The degree of alcohol is expressed in the percentage of the volume consisting of pure alcohol; 17 grams of sugar are needed for the must to produce 1% vol of alcohol by fermentation.
Theessential microbiological phenomenon that creates wine is alcoholic fermentation. The development of a type of yeast (Saccharomyces cerevisae), which is not exposed to the air, breaks down the sugar into alcohol and carbon dioxide; numerous by-products appear (glycerol, succinic acid, ethyl esters etc), and these enhance the aroma and taste of the wine. The process of fermentation produces heat, and the vat may need to be cooled down by refrigeration.
In some cases, malolactic fermentation occurs after alcoholic fermentation; with the aid of certain bacteria, the malic acid is broken down into lactic acid and carbon dioxide. This results in a lowering of acidity, a smoothing out and refining of the aroma and a more stable wine. Red wines are always improved by this process, but it is not always so for white wines. Yeast and bacteria exist naturally on the grapes; they develop during the procedures carried out in the wineries, and often they are all that is needed to start fermentation. However, the use of dried commercial yeast is becoming more common because it allows more control of the fermentation process and avoids certain defects (odours caused by reduction or lack of aeration) associated with some naturally occurring yeast varieties. In some cases, a modified stock allows dormant aromas specific to a particular variety (Sauvignon) to be released from non-aromatic characteristics already existing in the grape. In any case, the quality and the character of the wine depend not wholly on the quality of the grape but also on natural factors, such as exposure and soil.