So asks reader Dean (and Liz, and Darren, and Susan). The answer is a definitive “maybe”. There’s no question that bakers in the Bay Area have the edge when it comes to creating very sour breads. However truly sour, naturally-leavened loaves are possible in other regions of the country (or world), provided you can manipulate your starter’s moisture level, temperature, and rising/proofing times in the right way.
Allow me to explain. All bread starters are tag teams of yeasts and bacteria, with yeasts being primarily responsible for the rise, and bacteria for the flavor. The lion’s share of that flavor comes from acid, which is produced by different types of bacteria in varying amounts. As you might expect, the starter bacteria the thrive in the Bay Area, L. sanfranciscensis and L. pontis, are world champs in realm of acid production. L. sanfranciscensis produces unusually high levels of lactic acid, while L. pontis makes mostly acetic acid, which is the stuff that gives vinegar its sharp flavor.
The thing about these bacteria is that while they do thrive in Northern California, they can be found just about everywhere. Culturing them in large enough numbers is the trick.
Devoted sourdough bakers know that L. pontis likes cooler climates that are also a little on the dry side. Thus to encourage L. pontis growth, they’ll make their sourdough starters with a good deal less water. It’s a technique that can be replicated anywhere, and used with just about any bread that calls for a sponge. It requires a little experimentation, but the results are often striking. For example, I have a sandwich bread I make from time to time that’s starter-based. I’ve found that if I cut the water and make a stiffer starter, the final bread does have more of a tang than the standard version (note: I add the water that I left out of the sponge back to the dough in the mixing step).
Time and temperature can also be leveraged to increase dough sourness. As mentioned, L. pontis prefers cooler temperatures, so longer, cooler rises and proofs are preferred. Temperatures in the 60-degree (Fahrenheit) range are ideal, though they can be hard to achieve in a modern home, especially in the summer time. If you have a basement in an air conditioned house, you might try proofing your loaves down there.
Also, contrary to what most people think, lots of starter isn’t necessarily the way to achieve a sour bread. That’s because a lot of starter creates a more rapid rise (at least by sourdough standards), and rapid rises and proofs don’t give the bacteria the time they need produce large amounts of acid. A smaller amount of starter, like a smaller amount of yeast, will take time to work its magic in the dough. As it does so, it will be steadily making acid and souring your bread.
Other tips and tricks include the dough stretching I mentioned below, which not only helps spread the bugs around in the dough, it gives them lots of oxygen, which they also need to digest starch.
Not being a devoted bread head, I’ve never gotten heavily into this subject, thought I’d like to do more with sponges and preferments as there’s a whole little world to discover in there. Yes, I could always do one of the cheats of adding a little powdered acid or vinegar to a dough to give it sourdough-like flavor, but strangely, I think I’d feel guilty about it.