How does yeast make the bubble in wine?

Yeast doesn't directly create the bubbles in sparkling wine. Instead, it's a two-step process:

1. Fermentation:

* Yeast consumes sugar: Yeast is added to grape juice (must). It consumes the sugar in the must and converts it into alcohol and carbon dioxide (CO2) as a byproduct.

* CO2 is trapped: This CO2 is initially dissolved in the wine.

2. Second fermentation (for sparkling wine):

* Adding sugar and yeast: To create bubbles, sparkling wine undergoes a second fermentation. Winemakers add a small amount of sugar and yeast to the wine.

* CO2 production: The yeast consumes the sugar and produces more CO2. Since the wine is bottled under pressure, the CO2 cannot escape.

* Bubbles form: As the pressure builds, the CO2 dissolves less and less in the wine, forming tiny bubbles that rise to the top.

So, in summary:

* Yeast is responsible for producing CO2 during both fermentations.

* It's the pressure in the bottle that traps the CO2 and creates the bubbles in sparkling wine.

It's worth noting that different types of yeast are used for primary and secondary fermentations. The yeast used in the secondary fermentation is typically specially selected for its ability to produce high amounts of CO2.