Winemaking techniques vary and depend on the style of wine being made. At De Bortoli a “hands on’ approach in the vineyard and “hands off” approach in the winery reflects the family philosophy of allowing fruit and terroir to be fully expressed in every bottle.
Vintage
De Bortoli has vineyards in four diverse regions, the Riverina, Yarra Valley, King Valley and Hunter Valley. Vintage occurs in late summer through to early autumn, when the ripening process called ‘veraison’ rapidly accelerates. When the grapes are fully ripened they are harvested. In the Hunter vintage occurs from mid-January to early March, the Riverina from late January through to as late as May/June [for the late picked botrytis styles]. In the Yarra Valley and the King Valley from early March to late April.
Winemakers aim to achieve a balance of fruit, structure, texture and flavour. High quality fruit is essential to produce high quality wine. Generally white varieties are harvested before red varieties. Traditional hand picking is used for special parcels of fruit but the majority is machine picked to allow the fruit to be harvested in the cool of the night.
Crushing
When harvested, the fruit is delivered to the winery where it is crushed, stems removed then fermented. Once the fruit is crushed into the fermenters the grapes and juice is referred to as ‘must’.
White Wine
The must is drained and pressed and two fractions of juice are produced - ‘free run’ and ‘pressings.’ ‘Free run’ is the juice that drains freely from the press. ‘Pressings’ is the juice obtained by mechanically squeezing the must.
These parcels are kept separate until post fermentation blending. Both fractions of juice are clarified and a selected yeast strain is added to begin fermentation. Alternatively some wines may undergo “wild” yeast fermentation in which indigenous or natural yeasts ferment the wine. Depending on the wine, the temperature of the ferments can range between 13° - 17°C and last from 2 - 3 weeks until the yeast has converted the sugar to alcohol.
Chardonnay may be fermented and matured on yeast lees in French or American Oak. It may also undergo a type of secondary fermentation called malolactic fermentation [MLF] which converts malic acid to lactic acid and giving texture and complexity.
Other white wines such as Semillon, Sauvignon Blanc or Riesling may not be oaked at all and be fermented and stored in stainless steel until bottled. These winestyles are often bottled shortly after vintage, once fermentation, stabilisation, clarification and blending has occurred.
Red Wine
After crushing and de-stemming, selected yeast is added to the must and fermentation begins. Again the winemaker may choose that some wines undergo “wild” or natural yeast fermentation.
Juice from the must is taken from under the cap of the skins and used to irrigate the skins to extract colour and flavour from the skins. When done manually this is called ‘plunging’. The red must is fermented at temperatures between 22° - 30° C, usually over a 5 - 7 day period. Special parcels may be transferred into French or American oak barrels to complete fermentation. When the sugar has been converted into alcohol, and the colour and flavour have been extracted from the skins, the must is pressed.
After pressing, the wine undergoes a secondary or malolactic fermentation [MLF] that converts malic acid into lactic acid and gives the wine softness and texture. Once malo-lactic fermentation is complete the wine is clarified and stabilised before blending. For special parcels oak maturation in French or American oak may occur for anything from 9 - 12 months.
Oak Maturation
Most premium red wines and some premium white wines are matured in oak, either French or American. The trend is however is to pull back on oak and use a combination of new and used oak because all new oak can dominate the flavour of the wine.
Clarification and Stabilisation
Wines are clarified and stabilised before bottling. Clarification may be racking by gravity, as used with the premium Yarra Valley wines, or filtration. Tartrate stabilisation removes potassium bi-tartrate crystals. This is achieved by chilling the wine below 0° C.
