A number of questions have come in about barm (sourdough) starters the last few days. Though some of the specifics have varied, the main theme seems to be: how do I keep and use a starter on a long-term basis? Looking over in my section on barm starters, it appears that I never really covered that subject in detail. What an oversight! Well, better late than never I guess.
Keeping a starter is a very easy thing to do once you’re in the habit. I keep mine in a 2-quart container in the back of the fridge. It’s been there for years. Every time I set out to do a little starter-based baking I take a little of it out, then feed that bit, slowly building it up into the quantity I need. The main starter that stays in the fridge is what’s known, in baking parlance, as a “mother”.
A mother starter can live indefinitely, provided you take care of it, and over time develops a character that’s unique to your kitchen. As I’ve written often before, it’s a myth that homemade starters are cultures of local yeasts. Wild yeasts, yes, but most of the yeasts that make up your starter come out of the flour bag. Which is to say, they are yeasts that occur naturally on wheat berries as they grow in the field. When those wheat berries are ground into flour, at least some of the yeasts that have adhered to them end up in the flour. When you make a starter, they’re the yeasts that develop first. And every time you feed your starter, you introduce more. Thus the odds are good that most of your starter is comprised of yeast strains that originated in North Dakota or Kansas.
Which is not to say that those yeasts are all that’s in there. A starter is an ecosystem all it’s own, containing a wide variety of micro-flora and micro-fauna. And while the majority population may be from the Plains, eventually the locals will move in. The longer you keep the mother starter, the more entrenched those local yeasts and bacteria will become. So in time your mother will come to possess a character all its own. (Insert mom joke of your choice here).
The question then becomes: how do you maintain a mother starter once you have one? Again, it’s a very simple thing: you take a little of the mother out when you need some, and grow that small quantity into what you require for your recipe. You then replace what you took away (using some fresh-made starter “food”) so the mother never actually gets any smaller.
There are many philosophies on maintaining mothers. In busy bakeries mothers are constantly being depleted and refreshed. At the bakery I used to work in, we’d double or triple the volume of the mother starters nightly, use nearly all of it the next day, then repeat the process. At home it’s rare that a mother gets that sort of consistent workout. Usually is just sits in the fridge, staying dormant for days, weeks or even months. I’ve gone six months without using or even feeding mine. In those cases it may take two or three days to wake up the quantity I take from it — leaving it at room temperature and feeding it its own weight in 50-50 flour-water mix (by weight) every 8 hours or so. In those cases, I do end up throwing away a little starter, since I don’t want to keep doubling the thing at every feeding. I’ll take, say, 2 ounces of the mother out, give it an ounce of flour and an ounce of water, stir it and leave it at room temperature. Next feeding I’ll throw away half of what I’ve made (2 ounces), and repeat the process until I’m satisfied that what I have is fully awake.
Once my small quantity of starter is active, bubbly and predictable, I build it up to the quantity my recipe calls for, then use it. However I always try to make more than I need, so I can put a decent amount of lively starter back into the mother. That or I replace what I took with “starter food”, my usual 50-50 (by weight) flour-water mixture. Note that there’s no set strategy for maintaining a little-used mother. Some people, even when they don’t use it much, throw away half the mother every couple of weeks, replace what they took with “food” then put it back in the fridge to slowly bubble until they use or replenish it again.
Me, I rarely remember to do that. A lot of times I’ll go a loooong time without using my mother starter. In those cases, when I open it, it’s grey and clay-like, with a cloudy grey layer of liquid over the top (a mixture of water and alcohol). Ugly as that is, it’s still a perfectly usable mother. I simply stir the liquid back into it, take some out, and feed it as described above. In these cases I’ll throw quite a lot of the rank mother, and give what’s left a full feeding — of 100% of its weight — then refrigerate it.
I hope this all makes sense. Note that there may be times, especially if you become a busy sourdough baker, when you’ll use up almost all of your mother starter. Don’t worry. I’ve used virtually all of mine a time or two. The good news is that as long as there’s even a tiny amount left in the container, you can build it back. Just sprinkle in a little flour and water, stir it together with the scrapings that are left, and let it grow at room temperature for a few hours until that little amount is bubbly. Feed it again, rest it again, and feed it again until it’s back to where you want it. Mothers are bottomless wells of sourdough baking love. Which I guess is why they call them mothers.