How Yeast and Must Kick Off Wine Fermentation
At first glance, it might look like pastry cream being whipped up in a kitchen. But in reality, what you’re seeing is one of the most important steps in winemaking: the preparation of a yeast starter, or “pied de cuve,” mixed with grape must. This simple but essential process is what kickstarts fermentation, turning freshly pressed grape juice into wine.
What Is Must?
“Must” refers to freshly crushed grape juice, complete with skins, seeds, and pulp. It is the raw foundation of wine. The sugars naturally present in the must are the fuel for fermentation — and yeast is the engine that drives it.
The Role of Yeast in Fermentation
Yeast are microscopic fungi that feed on sugar. In winemaking, they transform the sugars in grape must into alcohol, carbon dioxide, and a whole spectrum of aromas and flavors. Without yeast, there is no fermentation — and therefore no wine.
There are two main approaches:
- Native (wild) yeasts, which occur naturally on grape skins and in the winery environment.
- Cultured yeasts, selected for reliability and specific aromatic profiles.
Preparing the Yeast Starter (Levain or Pied de Cuve)
Instead of adding dry yeast directly into large tanks, winemakers often prepare a starter mix. This involves combining yeast with a small volume of grape must, creating the perfect environment for the yeast to activate and multiply.
After a few hours, this lively mix is added into the main tank of must. Think of it as “waking up” the yeast before sending them to work on the full batch.
Why This Step Matters
Starting fermentation with a yeast starter has several benefits:
- Reliability: ensures fermentation begins quickly and smoothly.
- Consistency: reduces the risk of stuck or sluggish fermentations.
- Quality: healthy yeast populations bring out more refined aromas and flavors.
From Must to Wine
Once the starter mix is added, yeast cells begin consuming sugars across the entire tank. The process can last from a week to several weeks, depending on temperature, grape variety, and winemaking style.
At Château Canon Chaigneau, for example, this transformation is carefully monitored to balance elegance, precision, and the natural complexity of our terroir.
Conclusion
That foamy, swirling mix of yeast and must may look like a dessert recipe, but it’s actually the foundation of great wine. By preparing a yeast starter and adding it to the tanks, winemakers set fermentation in motion — the magical process that transforms grapes into the wines we love.