With the grapes carefully tended and picked – at Gusbourne we only use grapes grown in our own vineyards – the harvest arrives at the winery. When depends on the weather that spring and summer have provided, but typically mid-September. The grapes are fed into computer-controlled presses that let us vary the intensity of the juice extraction for each different grape variety: Pinot Noir have fragile skins, Pinot Meunier are more robust, and Chardonnay in between. As with virgin olive oil, the first free-run pressing produces the prestige juice.
Primary fermentation begins when we add yeasts. Over the next 7-10 days, the first lively chemical reactions occur as the juice (or must) experiences a hubbub of sugars, nutrients, carbon dioxide and oxygen as the yeasts consume the natural grape sugars and turn them into alcohol. During the transformation, Gusbourne Head Winemaker Charlie Holland monitors the temperatures and the condition of the must. Maintaining a relatively high 18-20C in thermostatically controlled stainless-steel vats ensures no evaporation of flavour or aromas.
The still wine resulting from primary fermentation is just the start of the journey. For the sparkling finished bottle, secondary fermentation is required.
Secondary fermentation takes place in bottle. A tirage liqueur starts the secondary fermentation within the bottle and the carbon dioxide produced from it forms the bubbles that turn the wine from still to sparkling. We do this three or four days in advance of bottling so it's acclimatised and ready for the wine. The wine is bottled under a crown cap with glass strong enough to withstand the pressure as the carbon dioxide builds and the bubbles form that turn the wine from still to effervescent.
And that, in its simplest articulation, is the early chemistry behind sparkling wine. Read what happens next in the journey from our cellar to your glass – the dark arts of how the wines are aged, including how natural sediment is captured by riddling, then frozen and expunged in the drama of disgorgement, in the article links below.
Like to find out more in person? Book one of our Vineyard, Discovery or Estate Tours to learn more about Gusbourne, explore the vineyards and taste some of our award-winning wines.
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