Is there leaven in grape juice?

* Leaven is a substance that causes bread to rise. It's typically a mixture of yeast and flour, or a sourdough starter.

* Grape juice is simply the juice extracted from grapes. It does not contain any yeast or other leavening agents.

However, grape juice can be fermented to make wine, which is a different process. During fermentation, yeast consumes the sugar in the grape juice and produces alcohol and carbon dioxide. This carbon dioxide can create bubbles in wine, but it's not the same as the leavening process in bread.