Sourdough Starters and Temperature
How many times have you heard… “My starter had great flavor but over time, the flavor and sour disappeared.”
I keep many starters going at the same time. I have some of them frozen and all of them dried. I also keep motherdough under refrigeration quite frequently.I have found out that it is important to keep your sourdough starter at the right temperature for long term storage. Both Raymond Calvel (chemist, professor and iconic baker)and Frank Sugihara (microbiologist and discoverer of the San Francisco bacteria/yeast) recommend keeping a sourdough starter above average refrigerator temperatures. Temperatures between “8 – 10C (46.4 – 50 F)” are recommended by Calvel any time storage is longer than 48 hours. Temperatures above 42 degrees F are recommended by Sugihara. Many bakers experience a lack of flavor in their starter after using it for awhile, or find the original flavor gone. Refrigerator storage may be the culprit, after all refrigerators are made to keep fooods cold enough to discourage bacterial growth.
My recommendation is to get a small dorm or trailer refrigerator and keep it dedicated just for your starters. Keep a refrigerator thermometer in it and adjust the controls until your temperature is somewhere between 42 – 50 degrees F. If you only keep one starter, keep it at room temperature and feed it smaller amounts until you are ready to use it, pouring out any excess when there is too much. If you have several starters, and do not have a dedicated refrigerator, try storing the extra starters you don’t plan on using for a while in the freezer. It may sound counterintuitive, but keeping a starter long term in the refrigerator will cause an eventual die off of the flavor causing bacteria, whereas if you make up a very low hydration piece of dough and store it, well covered in your freezer, the same bacteria will fare well, at least for a while. Tests on frozen sourdough cultures have shown that they keep well for at least a few months. Using a frost free freezer would not be ideal because they have a heating cycle which would shorten the life of the frozen starter. The constant heating and refreezing is not good for a frozen culture.
If you decide to find a dedicated refrigerator for your starters, it would be ideal if you could get a temperature controller to make sure the temperature is constant. You also have to realize that with the higher temperatures for storage, the starters would need to be refreshed more often than you were used to with a colder refrigerator. Some of the older refrigerators are small,have great insulation, have more sensitive controls, and will actually go below the “safe” temperature levels of food storage. Remember, don’t store your regular food in a dedicated refrigerator, the temperatures are in the danger zone for bacterial growth(that is what makes your starter culture happy).
For very long term storage, you can dry some of your starter and keep it in a cool, dry place. Keeping the dried starter in a hard sealed container will insure that bugs or rodents don’t have access. A starter dried and then sealed in a zip bag (with the name of the starter and the date recorded on the zip bag with an indelible marker), and then placed in a glass jar is ideal. Keeping a dried starter in the refrigerator isn’t a good idea because of the humidity in a refrigerator.
The very many people out there who feel that a starter once moved to another location, will take on the attributes of it’s new area and no longer be the same starter, were probably noticing the effects of long term refrigerator storage on their starter. The same microbiologist named above have stated that a stable, healthy culture, cared for properly, will remain the same culture wherever it is. A good, healthy culture of yogurt or Kefir will remain the same culture regardless of what milk is used to culture it, the same goes for cheeses, yeasts used for beers and wines, and many other cultured foods. If you have been working with a starter that lacks flavor, think about what it’s long term storage has been.