Temperature Affects Time

Temperature is one of the most important variables in making sourdough bread. It will affect how quickly your starter will rise and fall (or if it will rise and fall). The wild yeast in a sourdough starter love the temperature of 74-78 degrees Fahrenheit. This temperature is where those wild yeast – and the bacteria that make up a sourdough starter – are going to be the most active. If your starter/levain/dough is under 70 degrees, it’s going to take a lot longer for the fermentation process to take place. If your starter/levain/dough is above 80 degrees, this fermentation process can move too quickly, resulting in an overly sour taste. Always shoot for 74-78 degrees for the “room temperature” of your sourdough.

Water Temperature

Of all the ingredients added in sourdough bread, water is the main ingredient that is really easy for us to control the temperature of. This means that we can be strategic when adding water and make it warmer or colder to compensate if the starter/levain/dough temperature is not what we want it to be. Adding cool water will bring the temperature of our ingredients down. Adding warm water will increase the temperature of our ingredients.

Example: I take the temperature of each ingredient before mixing my bread. Using a thermometer I quickly check the temperature of the flour, salt and levain. They are all under 70 degrees. It is winter so I know the ambient temperature is in the 60s. I add hot (90-95 degree water) to my dough and mix it together. Then I take the temperature of the dough after mixing. It is 70 degrees. I put my dough in a bread proofer set at 78 degrees (or other warm place) because my dough is cold, and I want to bring the temperature up to my desired 74-78 degree range. I know that my dough may take a little longer to ferment because the dough temperature is cooler than it should be.

Too Hot and Too Cold

Sourdough performs really well anywhere from 70-80 degrees (optimal 74-78). The goal is to stay within that range for as much time as possible. So what happens if the dough (or starter/levain) get too hot or too cold?

• Too Cold (68 degrees and below): At these cold temperatures, fermentation will go very slowly and may even not take place at all.

• Too Hot (90 degrees or above): If the temperature of your dough is too hot, yeast will ferment quickly, often adding a more sour flavor to your bread. Temperatures above 120 degrees can kill the yeast. I try not to add water above 100 degrees Fahrenheit to my sourdough.

Ambient Temperature

I live in a place with four distinct changing seasons. In the summer my house is humid and hot (despite using A/C). In the winter it is cold and usually in the 60 degree range. Throughout spring and fall, the days will vary in temperature inside my house. This can make it difficult to have consistent results. I find that I am more frequently needing to work to warm up my dough in the winter than I am trying to cool it down in the summer. Here are a few ways I have used to keep my sourdough warm when the ambient temperature is cold:

• Pseudo-Proofing Box: Stick your sourdough in an oven with the oven turned OFF. Turn the light on in the oven and let the sourdough sit in there. Take the temperature with a thermometer every so often to make adjustments as needed–sometimes you need to turn the light off if the oven is getting too warm.
• Proofing Box: I recently purchased this Brod & Taylor proofing box. I absolutely love it. It folds up easily for storage and has made a huge difference in keeping my sourdough right in that 74-78 degree range.
• Finding other warm places: Near a fireplace or above an appliance are examples of places that are warmer. Check the dough with a thermometer to make adjustments if needed.