I was told that a FreshLoafer had asked about my method of sourdough maintenance. Now that my baking is done at home as needed, and not as daily production, my method might be pertinent to some FL bakers.
During my first baking job, I worked for a German woman in Northampton, Massachusetts. We used a rye culture for all the breads--rye, whole wheat, white. Before leaving that job, I began a rye culture of my own, on August 28, 1980. It wasn't for another 12 or 15 years that I began maintaining a liquid levain culture along with the rye. The rye culture was the backbone of the bakery I owned, and over the years it has brought me to six continents. Both cultures were fed daily, as the healthiest cultures always are. And how good it feels to know that well over a million loaves of bread have been generated by the cultures.
These days I bake once every week or two, and I only maintain the rye culture. I feed it daily. Here's how: 10 g ripe culture, 16 g water, 20 g whole rye flour. Pretty straightforward, right? However, I do make slight adjustments as the seasons come and go. For instance, this time of year--hot and humid in Vermont--I may start with just 7 or 8 grams of ripe culture to slow it down a bit. And I make it just slightly firmer during the hot months, as a firmer culture ripens more slowly than a looser one. And for that reason, I may increase the water weight by a gram or two in the winter to encourage full ripening (I heat with wood, so the house is pretty cool by morning). Occasionally I'll use some of the discard for waffles, pancakes, or crackers, but most days I discard it. Into the compost it goes. I certainly don't consider this to be "waste," as I'm sure all those many millions of sourdough bugs are contributing in their own way to the metabolism of the compost. I simply consider that the discard is changing its "job description."
If I am making a bread that requires a wheat culture, I simply feed some of the discard with wheat for a day or two before building the final sourdough.
The sourdough is kept on my baking table 24/7. If I am going away, I give a normal feed, then refrigerate it after two hours. The principle is that the yeasts can get a bit of a head start before a lot of acidity develops, and once refrigerated, the majority of the rye flour is still available for them to feed on. I think the longest I've kept it refrigerated in this way is about three weeks. It returns to full health almost instantly. This method also works well with firm levain cultures (making the build slightly firmer before refrigeration is a good idea). If I maintained a liquid levain culture and was leaving for awhile, I'd simply make it into a firm levain first.
I try to remember to dry some of the rye culture every year. I take maybe 10 grams of ripe culture and patiently rub it with roughly 100 g of whole rye. I put it into a square of cheesecloth or an old (clean!) cotton sock and leave it on my desk. I've successfully re-hydrated the culture after two-plus years of dormancy. I'm currently holding some dried culture back to see how it does after five years. It's a good idea for all bakers to keep some dried culture as a back-up, just in case. I also like to dry some as it preserves the culture's "DNA."
I guess if I decided to eat just one day a week and spend the majority of my life at 38F, I'd feed my culture just once a week too and refrigerate it the other days. However, I really enjoy seven days of nutritious eating each week. Although my trusty old rye culture doesn't speak English, it surely does communicate, and the message it sends is that it prefers daily meals too.