DENVER—For the record, baker Ismael De Sousa isn’t a fan of the word “sourdough.”
“I think this is the only place in the world where you call sourdough bread this thing,” said the owner of Reunion bakery in Denver. “Sourdough pretty much implies bread is sour and that’s a misconception.”
De Sousa prefers to call it naturally fermented or naturally leavened bread, and it’s the hallmark of his bakery where customers will find it in loaves, croissants, baguettes and more.
A few years ago, De Sousa began selling sourdough starter at the request of house-bound locals who took up hobby bread making during the COVID-19 pandemic. And the demand has continued. For $8, bakers can get “a good amount” of starter De Sousa has been feeding and cultivating for about six years and use it to make bread immediately.
Creating a starter from scratch is a tricky endeavor that requires having good base ingredients, an abundance of wild yeast to adequately kick-start fermentation, and a little bit of luck to avoid mold or other bacteria interfering with the process. Once it is made, though, bakers—both amateur and professional—tend to feed and care for their starter with zealous attention.
Still, having a healthy starter is only half the battle of baking, especially at altitude and in a climate as arid as Colorado’s. But De Sousa says baking in these conditions isn’t a mystery—it simply requires some scientific recipe adjustments made to match the local atmosphere.
Air is less dense at altitude than it is at sea level, and because of that, gases expand and create more volume, De Sousa said. Anyone who’s shopped for potato chips in Colorado, where bags balloon to their maximum capacity, has seen the physics of this in action.
Gluten is what expands when baking bread, and its capacity to hold air becomes more delicate because it’s being pushed to its limit. But pushing gluten past its limit can lead to a flat bake. De Sousa explained. “It’s easier to do what we bakers call over-ferment. Basically what you did (in that case) was you popped the balloon. It couldn’t hold any more air, so the air escaped.”
When working with sourdough, it’s vital to consider the starter’s expansion capacity even before you bake. De Sousa recommends putting the starter in a glass jar and marking its height prior to feeding. As you feed it, note how much it grows.
Typically, bakers wait until the starter has tripled in volume before using it to make bread. At altitude, De Sousa recommends waiting until it is two to two-and-a-half times its original size. That offers slightly more expansion capacity for the dough while it’s in the oven, he said.
“You need to see some expansion, but you need to control that expansion to the point your bread won’t over ferment or pop or won’t have any more capacity to hold air,” he said.
De Sousa also suggests lowering the bake temperature, extending the bake time, and adding extra water to correct for the dryness of the environment. Because water boils and evaporates at a lower temperature at altitude, these adjustments ensure that baked goods cook evenly and completely and that the gluten stays intact.
For baked goods aside from bread, De Sousa said lowering the amount of leavening agent, such as baking soda or baking powder, will also help maintain the gluten’s integrity.
“Everything will expand way too fast because it’s easier for things to expand here,” De Sousa said. “When it expands too fast, it will always collapse. It can be a cake or it could be a loaf of bread.”
The best thing you can do for your sourdough starter, De Sousa said, is feed it well.
“It’s a living thing, right? It likes good food,” he said. “Organic flours, fresh milk flours will make a big difference.”
Artisan Sourdough Bread Recipe From Reunion bakery
Ingredients•25 oz. organic bread flour
•7 oz. organic whole wheat flour
•3 oz. dark rye flour
•25 oz. warm water (85 degrees Fahrenheit)
•1 oz. of salt
•7 oz. mature, healthy starter
Mix all ingredients together and let them rest for 30 minutes. After the resting period, hand-knead for 5 minutes and let the dough rest in a warm place for an hour. Then knead or fold the dough onto itself for another 2 minutes, rest for another 30 minutes. Repeat the fold and rest for an hour to an hour and a half. Shape your dough into a bowl and reserve in the fridge. The next morning bake on a baking stone or in a Dutch oven at 480 degrees Fahrenheit for 45 minutes.
