Maximizing Yeast in SD Starter
Michael Wilson’s use of the highly yeasted Levito Madre (Pasta Madre) have interested me for years. Unfortunately (as far as I know) all of the definitive literature is written in Italian. Because of this I have not ventured into this endeavor.
I recently got in touch with Debra and asked her for help to develop a sourdough starter which prioritizes the yeast population over the LAB. Below is her reply, which has been posted with her permission. Hopefully others will find the information useful.
“You're in luck. It's not that difficult to shift the balance, and it can be done rather quickly, although changes in the organism profile will likely follow more slowly. The best way is to reduce hydration to a firm dough, 50-60% or whatever gets you to something that isn't sticky after you knead the flour in. Feed it 3x a day if you can. (If you want to see it lose all sourness, feed every 4-6 hours for a day or two.) Like always, you need to work out feeding ratios that get you to the next feed without being overripe or deflated, because that's when LAB are forging ahead. You don't need high temperatures for this, room temp works best, especially now that the weather is cooling off. The warmer it is, the more frequently it will need to be fed to keep LAB from increasing too much.
With a strong ap like King Arthur, I usually go 60% on the water and feed 1:3:5, 3:3:5, 5:3:5, or even 8:3:5 depending how long it will be going between feeds --- 12, 8, 4-6 hours or less, accordingly, or depending on temperature. You know the drill. You develop your own routine as you go. Taste along the way, because that and how much rise you get will tell you everything you need to know about the balance. You'll probably get about 4x rise once it has transitioned and stabilized, provided you have the gluten structure to support that.
So the factors that favor yeast are: white flour, low hydration, more frequent feeding, and moderate-low temperature. This kind of starter makes great pain au levain, and I'll bet it would be the perfect choice for sourdough baguettes too. I don't know if high temperature is essential for the right species profile of a good panettone starter (it could be), but if you choose that route, just remember the higher the temp, the shorter the feeding intervals need to be to keep LAB in check.“