Winemaking 101: How White Wine Is Made
Ever wonder, as you sip that glass of Chardonnay or Sauvignon Blanc, how it was made? Fermented grape juice of course. But what does that mean? And what choices are made along the way? Here’s a bird’s eye view of how wine is made, from start to finish.
Step 1: Harvest
The first decision is when to harvest. The longer the grapes are left to ripen on the vine the more sugars accumulate in the grapes. When to harvest depends on many things. Winemakers use a mix of techniques from physically tasting the grapes to the use of technical analysis. The style of wine being made has a major bearing on when to harvest.
In the northern hemisphere most grapes are harvested between early September and November. Once harvested the grapes are usually sorted to eliminate bunches that don’t make the quality grade required by the winemaker.
Step 2: Crush and Destem
Once sorted, if it is a white wine the grapes are usually destemmed and gently crushed, just enough to break open the skins. Crushing enables the winemaker to extract more juice from the berry during subsequent pressing.
For certain wines, such as Champagne and sparkling wines, this step is avoided, and the grapes undergo instead what is called ‘whole-cluster pressing’.
Step 3: A ‘Cold Soak’
Before pressing, some winemakers elect to do what is called a ‘cold-soak’ or pre-fermentation maceration (PFM). As white wines are fermented off the skins, the PFM is used to extract additional aromas and flavor from the skins into the juice. This was a particular trend for most white wines a few years ago but has somewhat subsided.
Step 4: Pressing the Juice
Next step is pressing the juice from the skins. The gentler the pressing the finer the juice, or ‘must‘ as it is now called.
Once you have the must, it is ready for fermentation. Usually there is a period of cold settling – to allow solids in the juice to fall to the bottom – which are then racked off leaving a clearer juice. Each winemaker has his/her own preference on must clarity.
Step 5: Alcoholic Fermentation
The important bit – converting the sugars to alcohol. Fermentation requires the action of yeasts to convert the sugars to alcohol. These yeasts can be the natural yeasts from the vineyard, or specially selected, cultured yeasts. Cultured yeasts are much easier to control and ensure a more consistent fermentation. Natural yeasts, on the other hard, ensure a truer manifestation of the vineyard’s terroir, but are less reliable. Fermentations can be more challenging and can sometime be a bit sluggish. Each has its own set of advantages and disadvantages.
Fermentation vessel is a big decision – oak, stainless steel or other inert vessel. Because of its affinity with oak, Chardonnay is often fermented in small oak barrels. In contrast aromatic grapes such as Riesling or Sauvignon Blanc are typically fermented in stainless steel or other inert vessels to preserve their vibrant aromas and flavors.
Fermentation temperature also impacts the wine. Overall, white wines are typically fermented at cooler temperatures than red. The cooler the temperature the more well-preserved the primary fruit aromas and flavors. Warmer temperatures make for a more structured wine.
Typically when the yeasts have converted all the sugars to alcohol the fermentation is over and you have a dry wine. However, if the intended style off dry or medium sweet, the winemaker will stop the fermentation before all the sugars have been converted, leaving the desired amount of residual sugar.
Step 6: Malolactic Fermentation (MLF)
After the alcoholic fermentation, some white wines go through a process called ‘malolactic fermentation’. Technically this is not a true fermentation but rather a conversion of any remaining ‘tart’ malic acid (think green apples) in the wine to the softer lactic acid (think milk). Once again, Chardonnay is one of the main wines to undergo full or partial malolactic fermentation. Ever notice that many Chardonnay wines have a buttery note? Well, in part due to this process.
Step 7: Lees Ageing
When all the fermentation is over, the new wine is resting on all the dead yeast cells, called ‘lees’. The big or heavy lees are usually racked (drained off) off fairly quickly. Many winemakers choose to leave the new wine on the remaining ‘fine’ lees for a period of time – anything from a few weeks to several months and sometimes years. Ageing on the lees adds texture, palate weight and complexity to the wine. It also helps keep the wine fresh while waiting to be bottled.
During this time, some winemakers, again particularly with Chardonnay, do what is called ‘battonnage’ – stirring of the lees, to give a more creamy texture to the wine.
Step 8: Blending
Blending is a critical in achieving the final desired style. Wines made from a mix of different grape varieties are probably what we think of first when we think of blends. But varietal wines are very often blends also – blends from different vineyards, blends of wines from different vats that were treated differently during winemaking or maturation. Blending enables the winemaker to achieve smoothness and consistency in a wine.
Step 9: Finishing
The next step is ‘finishing’ before bottling. This involves a number of steps whereby the new wine is clarified and stabilized. Winemakers try to minimize the number of treatments, whilst at the same time ensuring that the wine is physically, chemically and microbially stable. For example wines with residual sugar need to be sterile filtrated to ensure that there is not even one little yeast cell (aka “yeasty-beasty”) remaining that could start a re-fermentation in the bottle.
Step 10: Packaging
Once all the finishing procedures are over, the wine is ready for packaging, in bottle or whatever packaging format is desired for the wine.
After a further period of settling the wines typically start to make their way to market for us to enjoy. And I hope you do.
Mary’s white wines recommendations for this week
• 2007 Château du Champ des Treilles Blanc, Sainte-Foy Bordeaux, $14 – This is a classic white Bordeaux blend made from Sauvignon Blanc, Semillon and Muscadelle. Only natural yeasts used. Unoaked, fermentation in stainless steel vats and aged on the fine lees before blending. Biodynamically farmed vineyards. Delicious with great minerality and flavor intensity – apricot, tangerine, citrus, hints of spice and honeysuckle. Excellent value.
• 2008 Montes Alpha, Chardonnay, Casablanca, Chile $25 – Barrel fermented and aged. This is a big wine, full-bodied and powerful with intense aromas and flavors. Very well structured. Layers of ripe stone fruit, pear, kumquat, cream and toasty vanilla. Smooth on the palate and long finish.
• 2010 Kim Crawford Sauvignon Blanc, Marlborough, $16 – A classic New Zealand Sauvignon Blanc. Unoaked, fermented at cool temperatures in stainless steel to preserve the vibrant fruit. It shows lots of lovely ripe citrus and tropical fruit and a refreshing grassiness that persists across the palate.
• 2009 Martín Codax Albariño, Rías Baixas, Spain, $13 – Made from 100% Albarino grapes. Cool fermentation in stainless steel, cultured yeasts and some lees ageing before bottling. Crisp and packed with bright youthful fruit – tangerine, grapefruit and white peach and hints of tropical fruit and flowers and a slight salty tang.
Until next week, enjoy!
Mary Gorman-McAdams, DWS, is a New York based wine educator, freelance writer and consultant. She holds the Diploma in Wine & Spirits from the Wine and Spirits Education Trust (WSET), and is a candidate in the Master of Wine Program.