Storing sourdough starter short & long term
I’ve been baking bread nearly every week at home for more than 10 years now. After several failed attempts to get a sourdough starter going I finally was successful about 18 months ago. After feeding my starter nearly every day for the first 6-8 weeks and making several successful loaves, I began to worry about losing the starter to contamination (or neglect). I wanted access to a good starter when I felt like sourdoughs but I didn’t want to feel as though I was tied to keeping the starter going daily (or even weekly) for the rest of my life. I really wanted to be able to put it away for a while (months at a time), but go back to my starter when I felt the urge for sourdoughs in the future. So I started looking into how to store my starter.
I came across a post here on The Fresh Loaf (http://www.thefreshloaf.com/node/6737/help-storingfreezing-starter-please) in which Mike Avery said he kept starters of 65% hydration “in the fridge far longer than I care to admit with good results.” In that same post, Bill (bwraith) said he too kept 65% hydration starters in the fridge, for as much as 6 months! Mike said he didn’t like to leave the starter more than 2-3 months without feeding.
Obviously this is what I was looking for, but questions still remained. How long can I really leave it? Should it be refrigerated, or frozen? Although it worked for Bill long term (6 months), would it really work for me for that long? I decided to do an experiment. I took my robust 100% hydration starter, made it into a 65% hydration starter, split it into eight (8) aliquots of 50g (1/4 cup) each I refrigerated 4 of the aliquots and froze the other 4 aliquots, and decided to take an aliquot of each out at various times later (1, 3, 6 and 12 months) to see how well they reconstituted my starter.
At each time point I took the 50g of refrigerated/frozen starter, let it warm for about 30 minutes, and then added 200g of water. After a thorough mix, I then added 200g of flour, stirred until smooth, and then watched and waited.
Refrigerated – Smelled quite sour but had little if any liquid on top. Doubled in 30 hours. Looked and smelled great.
Frozen – When thawed there was no real scent and no liquid of any kind on top. No activity seen at 24 or 36 hr. By 48 hr there were a few small bubbles on top, and by 72 hr it had doubled. At this point it looked bubbly and smelled like it should.
Refrigerated – Sample smelled very sour at this point and had a gray colored layer on top of it. There was no liquid on top. The starter underneath was “whiter” and when stirred it made a surprisingly watery mix. Activity noted at 12 hours and had doubled by 24 hours. Had fallen by 48 hours but was bubbly and smelled great at that point.
Frozen – When thawed the starter had a very faint sour scent and a shiny wet surface, but no accumulated liquid on top. Some slight bubble activity at 36 hours. At 48 hr it had quite a few large bubbles on top. I decided to refresh it at this point by removing 50g and adding this to 100g water and 100g flour (I also kept and watched the original frozen starter). By 72hr the original frozen starter had lots of small bubbles on top and increased in volume by about 25% and it had doubled and was just fine by 84 hr. The refreshed frozen starter had not increased in volume at all by 72hr, had grown about 25% by 84 hr, and it had doubled by 96 hr. Looks and smells just fine at this point.
Refrigerated – As at 3 months the sample smelled very sour and had a gray layer on top of it. There was no liquid on top. The starter underneath was “whiter” and when stirred it made a watery mix. After 24 hr this sample had increased in volume by about 60% and it doubled by 30 hr. At this point the top was bubbly and wet and it smelled nice and sour. No problems here!
Frozen – No smell, no change in color, kind of a sticky lump when warmed. There was slight bubble activity at 24 hours. At 72 hr it had a distinct sour smell but it hadn’t changed much in volume from the 24 hr sample. So I again decided to refresh it at this point by removing 50g and adding this to 100g water and 100g flour (I also kept and watched the original frozen starter). By 96 hr the original frozen starter had doubled and was just fine. The refreshed frozen starter had also doubled in volume and smelled/looked just fine by 96 hr.
Refrigerated – The sample was very gray colored both on top and underneath. There was some liquid on top of it, and even when stirred it had an “off” scent. The smell reminded me of cider vinegar. No activity at 24 or 48 hr although it did smell a little less at 48 hr than it did at the beginning. I decided to try the “refresh” trick at 60 hr by removing 50g and adding this to 100g water and 100g flour (I also kept and watched the original starter). By 84 hr there was perhaps a hint of activity, but no more activity at 96 hr. I tried a second refresh at 96 hr. At 144 hr (6 days) there is no sign of activity in any of the 3 refrigerated samples. At this point it still had a bit of a vinegar odor and had some gray/green hooch on top.
Frozen – Again no smell, no change in color, kind of a sticky lump when warmed. No activity at 24 or 48 hr. Like the refrigerated sample I decided to try the “refresh” trick at 60 hr by removing 50g and adding this to 100g water and 100g flour (I also kept and watched the original starter). No activity at 72 hr there was perhaps a hint of activity, but no real activity at 96 hr. I tried a second refresh at 96 hr. By 108 hr there was a 50% increase in volume of this second refresh sample, and by 120 hr it had at least doubled in bulk. At this point (120hr) it had lots of small bubbles on top and it smelled like a good healthy sourdough starter should. At 132 hr I took all (~200g) of this 96hr refresh sample and added 200g of water and 200g of flour to see if it would work as a real starter. It had more than doubled 3 hours later demonstrating that at this point it was a robust starter.
Conclusions: It is clear from this experiment that storing starter at 65% hydration in the refrigerator is fine (and probably the method of choice) for at least 6 months but a year or more is probably asking too much. Freezing the starter works fine, even out to a year or more. However it takes longer to restore a vigorous starter from the frozen state.
Early on in this experiment I came to the conclusion that keeping a sourdough starter in the refrigerator for a month or two (or even six) is absolutely no problem. It is now my routine. I pull it out every 2-8 weeks or so, feed it for a weekend (probably use it once or twice), and put it back in the fridge. I also keep an aliquot at 65% frozen as a backup, and I plan to refresh this backup on an annual basis. (I also must admit that I don't always go to the trouble of making a 65% starter for refrigeration. If I'm planning on taking it out again in the next few weeks I usually just put my 100% starter in the fridge.)
In the end, I now feel much less stressed about ignoring my starter in the back of the refrigerator for a few months. Thanks to Mike and Bill for their inspiration in this experiment.