can form salts with the tartaric acid: Potassium bitartrate and the neutral calcium tartrate at the pH of the wine. For these, when their solubility threshold is reached, they settle and contribute to de-acidify the wort. In the southern regions where acidity is sometimes a little lacking this may be a cause of failure of extra acidity. Winemaking White winemaking is broadly similar to red winemaking although details differ when making the two types. White wine is made from white or black grapes (but always with white flesh, the grapes with coloured flesh are called Teinturier meaning coloured juice). Once harvested, the grapes are pressed and only the juice is extracted which is called wort. The wort is put into tanks for fermentation where sugar is transformed into alcohol by yeast present on the grapes. The grape harvest Grape maturity depends on the requirement of the final product. For a sweet white wine, whether fortified or natural, sugar is the key criterion. For a dry white wine, technological maturity is calculated and the fruit is harvested just before (usually eight days) the maturity of the sugar. At this point the relationship between sugar and acid is optimal. Further, low acidity will cause the future wine to be unbalanced with excess alcohol and lack of liveliness. In addition, the flavour will be less fresh and less vivid. Traditional hand harvesting of whole bunches has been increasingly challenged by the harvesting machine for dry white wines, an economic choice but not always a qualitative one. The fragility of the grape requires either a rapid transfer to the Winery, or protection from oxidation. When the transport time between vine and winery is long, the harvest can be refrigerated and kept away from oxygen using nitrogen or dry ice. However, for some sweet wines, a successful harvest requires manual work and training for pickers to pick only clusters where the berries have reached optimum ripeness or have been affected by noble rot (for the Sélection de Grains Nobles). For sparkling wines hand picking is recommended and it is absolutely necessary for white wines from grapes with coloured skin. Treatments before fermentation The first step in processing the grapes at the winery is to separate the components of the wort that are needed from the unwanted parts. The process followed at this stage will largely determine the future quality of the wine. For this, the