Have you ever wondered if you can add yeast to your sourdough starter? It's a question I've been asked many times over the past few years and I decided to write about it so that I can share my answer with anyone else that might be interested.
The short answer is - yes you can add yeast to your sourdough starter. There's absolutely nothing stopping you (and certainly no sourdough shaming). However, if you do add some commercial yeast to your starter, it will then have that strain of yeast as part of it's established colony which would mean that it won't be a "true sourdough starter". This may not be a problem for you, if you aren't a sourdough purist (and again, there's no sourdough shaming here).
You can find instructions for making a sourdough starter here.
What is Sourdough Starter ... and How is it Different From Yeast?
A sourdough starter is a mixture of equal amounts of flour and water that has been left to ferment at room temperature. As the mixture ferments over a couple of weeks, it becomes home to a colony of natural yeast and lactic acid bacteria, which live in a symbiotic relationship. The yeasts break down the carbohydrates in the flour into simple sugars, producing carbon dioxide. The carbon dioxide creates bubbles in the dough, causing it to rise. You can read more about how a sourdough starter works here.
An active sourdough starter is different from yeast (whether it be active dry yeast, fresh yeast or even instant yeast) because commercial yeast contain only one, refined strain of yeast - saccharomyces cerevisiae. It is strong and reliable and will raise bread dough in a fast and efficient manner.
Sourdough starter on the other hand generally contains more than one strain of yeast. These wild yeasts are less reliable and can take much longer to rise a loaf of bread.
What Happens When You Add Yeast to a Sourdough Starter?
If you add yeast to a sourdough starter, you will be introducing this honed and reliable strain of yeast to the colony of wild yeast. You'll speed up the fermentation process, and here lies the issue. The yeast will feed on the sugars in the dough and produce carbon dioxide, causing the dough to rise faster. But it is the slow fermentation process which produces the unique flavor and texture of sourdough bread.
Adding commercial yeast to your sourdough starter will result in a change of flavor and texture in your sourdough bread.
Sourdough bread made with commercial yeast will have a milder flavor and less of the characteristic tanginess that comes from a naturally fermented sourdough starter. And in fact, you could argue that it is then not real sourdough bread.
You can of course manipulate some of these flavors by choosing to use whole grain flours like rye flour or spelt flour or whole wheat flour as well as manipulating the temperature, however it can be very hard to get a true San Francisco sourdough flavor when using a larger amount of commercial yeast.
Is a Sourdough Starter Made from Yeast a Real Sourdough Starter?
Technically, sourdough cultures made from yeast are not real sourdough starters. A true sourdough starter relies on the natural yeasts and bacteria present in the flour and the environment. Adding commercial yeast to the mix may speed up the fermentation process, but it won't produce the same complex flavors and textures that come from a naturally fermented starter.
Technically a sourdough starter made from commercial yeast is referred to as a Poolish and is really just a commercial yeast culture.
Now like I said, there's certainly no sourdough shaming here. If you do want to add a pinch of yeast to your sourdough starter, I highly recommend just using a tiny pinch. This will be plenty. I also recommend keeping your starter on the stiffer side. The increased activity that comes from the commercial yeast will tend to make your sourdough starter too runny. Reduce the amount of water a little to give you a thicker mixture.
Can You Use Commercial Yeast To Boost Your Sourdough Starter?
While it might seem like a good idea to add a pinch of yeast to your sourdough culture to give it a boost or to strengthen it, it's not something that I recommend doing. There are much better ways to strengthen your sourdough starter without compromising the wild yeast colonies that live inside your jar. A healthy starter takes time - period. Generally a couple weeks, but in reality it takes several months before you'll have the best results. But believe me, it's well worth the wait!
There's really no such thing as a "quick sourdough starter" - sourdough is a traditional method of leavening bread which takes time and patience. It's rooted in a deep sourdough bread making history that spans the globe. If you're looking for a faster way to make a sourdough starter, you might be better off buying a starter, rather than trying to create one from scratch.
Alternatively, if you're worried about wasting too much flour, then these small sourdough starter instructions might be of interest.
Instead of adding the commercial yeast to your sourdough starter, it's better to add a pinch to your sourdough bread dough, if you want to give it some help.
What If You Add Yeast to Your Sourdough Bread?
The same principle applies if you add commercial yeast to your sourdough bread dough - you would just need a little bit of yeast to "spike" your dough. There's really nothing wrong with adding a pinch of yeast to your sourdough bread recipe. A pinch of yeast will still give you a good sourdough flavor, but is more likely to give you a better oven spring when it hits the oven.
You can see what happens when you add yeast to sourdough by looking at sourdough discard recipes like this easy sourdough sandwich bread recipe and this sourdough discard bread recipe, which use a little yeast to boost the unfed sourdough starter.
One thing you do need to take note of is that if you add some store-bought yeast to your sourdough, it will not have the health benefits that a traditional long fermented sourdough will have. This means that it will not be suitable for people with gluten intolerances. Even when using a traditional starter, adding yeast means that the phytic acid levels won't be as reduced as if you were making a traditional sourdough recipe.
Favorite Hybrid Sourdough Recipes
Sourdough recipes with added yeast are usually referred to as "hybrid" recipes. There are lots of ways you can use your sourdough starter (or sourdough discard) along with a little yeast to create a hybrid sourdough bake. Here are some of my favorite recipes for sourdough hybrids: