What causes alcohol production to stop in fermentation?

Fermentation is a process where yeast converts sugars into alcohol and carbon dioxide. The production of alcohol continues as long as there are fermentable sugars present in the mixture. Therefore, once all the sugars have been consumed by the yeast, fermentation halts because there is no longer a substrate for the yeast to convert. This leads to the cessation of alcohol production since the yeast needs sugar to create alcohol.

Understanding this process is crucial for winemaking, as it influences the final alcohol content of the wine. If the fermentation stops prematurely, it can result in a wine that is sweeter or has lower alcohol content than intended, while a complete fermentation will result in a drier wine with higher alcohol levels.

The other options present factors that can influence fermentation but do not directly cause alcohol production to stop. For example, excessive temperatures can stress yeast but it is the sugar availability that directly affects alcohol production. Sealing the fermentation vessel can impact oxygen levels but does not directly cause the cessation of alcohol unless sugar is depleted. Crushing grapes initiates fermentation but is not a trigger for stopping it.