More Rules for Sourdough Starter Maintenance
On starter "peaks", kitchen faeries, and more.
I’m about to leave for my honeymoon in Japan, so this newsletter will take a little breather until later this month. See you in a few weeks!
Your Starter’s Peak Doesn’t Matter the Way You Think it Does
Bakers are told to use their starter at its peak in its container, the a visual high point before the starter starts to collapse.
There are a number of reasons why it’s not so simple. For one thing, the tendency of your starter to collapse at a certain time is based largely on the dimensions of its container. The same starter kept in a container that is wide relative to its height won’t collapse as readily as a container that’s tall relative to its width. Why? Gravity.
Additionally and perhaps counter-intuitively, the same starter kept in a wide container will ferment at a slightly slower rate than it would if kept in a tall container in most kitchens. An increase in surface area means an increase of heat exchange with the environment, and conversely, a decrease in surface area means that more heat that can be preserved within the sourdough starter.1
Another factor is flour. All-purpose flour generally has a higher falling number than bread flour, indicating that its enzymatic activity is reduced, which implies that our rate of fermentation will be slower.
But this knowledge doesn’t help us that much. For example, a 100% hydration liquid starter maintained with King Arthur All-Purpose Flour will rise to a peak, recede a little, then rise back up to a peak that looks almost foamy. Which peak should we target?2 When is it safe to feed the starter again without the risk of reducing its potency?3
King Arthur Bread Flour has a lower falling number than King Arthur All-Purpose Flour, and its additional protein content that favors extensibility over elasticity. Visually, a starter fed with it will rise and fall faster than one fed with All-Purpose, but a sensory analysis of a starter at this point will reveal the presence of minimal acidity and an aroma that doesn’t remind you much of sourdough bread.
We can’t learn that much from a peak observed in isolation. I can stir a starter that has fallen and it will rise to another peak. In typical environments, most starters don’t reach maximum cell density until an hour or two after they’ve peaked and start to recede.
So what can we do?
The best way to tell if a starter is ready to use is to take an qualitative approach:
First, inspect it visually. Don’t look for a peak, but instead, determine if your starter looks well-fermented. Is there evidence of even fermentation throughout, or are there visible gradients of fermentation? If you’re using a stiff starter, is your starter flattened on top? This is a great place to use it.
Make a mental note of how your starter smells and tastes at this point.
Make bread with it. Are you happy with the results? If not, change up your approach next time and repeat this analysis.
The conventional wisdom on sourdough preferments is both descriptive and prescriptive, but research papers all seem to point to one thing: We understand sourdough less than we think we do.
Doubling and Tripling Doesn’t Necessarily Matter
See above. The perceptible increase in volume will occur relative to the shape of the container. This applies to sourdough starters the same as it does to doughs. You have to observe how sourdough systems behave relative to the containers and environment that you have.
Don’t Use a Towel as a Lid
There is the romantic belief that a sourdough starter is born of magical wild-caught yeast that we trap like fireflies, and I’m here to dispel you of that notion. The dominant populations in any given sourdough starter are those that are present on the grain itself at the time of harvest. Of course, it’s more complicated than that, as we are also talking about yeasts and bacteria that can survive in an acidified environment, which represents only a fraction of what is in your flour.
New populations will be introduced to your culture over time through ordinary feedings, but these strains are by far a minority and have less of an impact on flavor and aroma than most people think.
In light of that, there is no need to keep your starter exposed to the air. In the event that you can keep your starter at its ideal temperature, you probably don’t have an environment that is as humid as the headspace of a closed container.
An ordinary jar is just fine. Many people believe they have to keep the lid loose to prevent it from blowing off, but you’re maintaining a sourdough starter, not a potato cannon. If you have plenty of headroom in your container for the starter to expand, it doesn’t really matter if your lid is tightly closed or not.
For bulk fermentation containers, use a sealed container. I tend to use a Cambro or a mixing bowl with a pizza pan as its lid.
Maintain a Warm Sourdough Starter, Even If You Can’t Bulk Ferment at Warm Temperatures
If you can maintain a sourdough starter in an environment that’s a little warmer than room temperature—at least 75 °F—you’ll have a culture that is effective at leavening bread even if you don’t have a good way to keep your dough itself warm during bulk fermentation.
This bread was bulk fermented at 70 °F but leavened with a starter kept warm and fed every 12 hours.
I don’t have any specific advice here other than to do it.
Happy baking!
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Though I should note, this is less of a factor when we’re talking about extremely small amounts of starter or dough. They will always try to reach an equilibrium.
We should target the second one.
Usually around the second peak.