If you add a teaspoon of yeast to bread dough that is already being made with a sourdough starter, it can provide a boost to the fermentation process and help the dough rise more quickly. The sourdough starter itself is a natural leavening agent that contains wild yeast and lactic acid bacteria. These microorganisms work together to ferment the dough and create carbon dioxide gas, which gives the bread its rise and airy texture.
By adding additional commercial yeast to the dough, you introduce a different strain of yeast that is commonly used in bread baking. This can help speed up the fermentation process and provide a stronger rise. The commercial yeast is more predictable and faster-acting compared to the wild yeast in the sourdough starter, which can be beneficial if you're looking for a quicker rise or want to ensure a consistent result.
However, it's important to note that using commercial yeast in a sourdough bread recipe can affect the flavor and characteristics of the final product. The longer fermentation time of sourdough allows for more complex flavors to develop, while adding commercial yeast can result in a milder flavor profile. If you prefer the distinct tangy flavor of sourdough bread, it's generally best to rely solely on the sourdough starter for leavening.
Ultimately, the decision to add commercial yeast to your sourdough bread dough is a personal preference. It can be a useful technique if you're in a hurry or if your sourdough starter needs a boost in activity. Just be aware that it may alter the flavor and characteristics of the bread compared to using the sourdough starter alone.