How A Grape Becomes Wine – The Winemaker

By Dan Hutton on October 27, 2010 in

“Wine is sunlight, held together by water.” – Galileo Galilei

Most winemakers work pretty closely with viticulturalists in terms of what happens to the grapes in the vineyard. Often the winemaker’s most difficult task is to work out when to pick the grapes.

As a grape ripens, acid levels drop and sugar levels increase. The sugar is what ferments into alcohol so they want to make sure they’ve got enough there to make a decent wine. They can’t just leave a grape until it’s super sweet though, because they won’t have enough acid in the wine, which is essential for wine structure.

Different grapes ripen at different rates, so some grapes will be picked earlier in the season while others will be picked towards the end. The winemaker and viticulturalist also need to work out which bunches of grapes should be harvested as different bunches ripen at different rates. Some wine styles even use single berry harvesting!

Once the grapes are picked, they’re taken to the winery where they may go through a ‘de-stemmer’. The grapes then move on to a crusher. When all of the grapes are piled into the crusher, some of them naturally burst from pressure – this juice is called ‘free run’ juice and is usually seen as the purest. The grapes are then gently pressed to break the skins of more berries and release more juice. Grapes can be pressed numerous times but the more you press them, the lower the juice quality.

Once the juice is extracted, the grapes are moved to fermenting tanks. The colour for most red wines comes from the skins, so red grapes are fermented with their skins on (and sometimes with the stems if extra tannin is required). Longer skin contact means more colour extraction and more tannin. These skins form a ‘cap’ on the fermenting tank by floating to the surface, so they need to be plunged back into the wine each day. Many rosé wines are made with red grapes that are given only minimal skin contact to develop a bit of colour but not much tannin.

To get the fermentation started, the winemaker needs yeast. Many grapes have their own yeast on them when they’re picked (there’s a powdery coat on them), but the winemaker may not want to use this unpredictable ‘wild’ yeast. There are many different yeast strains that can be used depending on which grape they’re fermenting – different strains will give different flavours.
When to stop this fermentation is also important. During fermentation, sugar is becoming alcohol so the winemaker needs to decide whether they want some sweetness in the finished product or if they want to ferment the wine to dryness?

Once the primary fermentation is complete, the wine is moved into airtight storage tanks to undergo a secondary fermentation. This may occur in wooden barrels to introduce vanilla flavours and texture into the wine. Even the choice of oak barrel is important as oak from different areas give the wine different characteristics.

At this stage, some wines may go through malolactic fermentation, whereby mallic acid is fermented into lactic acid, giving the wine a buttery texture and flavour.

Next, the winemaker needs to run loads of tests to determine when to bottle the wine. The winemaker also needs to decide kind of closure to use, whether to blend certain barrels together and what to leave aside for a few more years for a “reserve” wine. Then the final decision is when to release it to the public.

And of course, it’s a whole different story for sparkling wines!