Sourdough starter began acting strange after storing in fridge

Question

I recently began developing a sourdough starter and it seemed much easier than it sounded - within a few days it was growing well and smelled good (like yeasty bread dough). On about day 5 or 6, I had to go away for the weekend, and so I stored the starter in my fridge, and now it's acting sort of strange.

Before I went away, I fed the starter and put it in the fridge right away. When I came back 2 days later it had still grown in the fridge. Not as much as usual; before my trip the starter was maybe growing from 1 cup to almost 3 cups, now it was closer to two. This, I think is expected - being in the fridge would retard the yeast's activities.

In any case, I took out the starter and let it sit for an hour or two to get it back to a more normal room temperature, and fed it again. (I think it missed 1, maybe 2 feedings because I was out of town.)

Anyway, now that I am back to regular feedings the starter is still growing well and then falling (which I believe is what it should do when it eats up all the food). But it's doing it really fast. I.e. in less than 12 hours. And then the starter begins to smell weird, like alcohol. It's pretty intense.

What happened to the yeasty smell? That was much nicer than this new, alcoholic development. I read online that the alcohol smell comes when the yeast run out of food and switch from aerobic to anaerobic mode. Should I really be feeding it more than once a day?

Answer 1

Sourdough starters are rarely completely ruined, unless you're growing significant amounts of mold or something.

It is possible that your refrigerated "break" early in establishing your starter ended up hurting the yeast population and accidentally selected for something else (perhaps undesirable bacteria) that is now growing and creating odd odors.

It's also possible that your starter is perfectly healthy and well-established. A strong starter should often rise and begin to fall in 12 hours or less. Mature starters tend to go through a cycle where they smell yeasty as they are expanding, have alcohol notes around the time of collapse, and then acidic (vinegar/acetic acid and lactic acid) notes as they age further, due to bacteria converting the yeast waste products into acids.

Have you tried to bake with your starter yet? I'd see how well it works and whether it can successfully leaven bread dough. If so, it's probably fine. Starters do often go through periods of odd smells and weird behavior in the first couple weeks, but they'll stabilize after more regular feedings as a more consistent set of microorganisms becomes permanently established.

You don't mention any liquid floating on top ("hooch") or any discoloration. If those were appearing, I might be a little more concerned. If not, try baking a small loaf with it, and see what happens. My guess is that it won't be very sour, but with a feeding regime like you have, it probably shouldn't be.

Lastly, you asked about whether more frequent feeding is required. I don't think so, given how much you dilute your starter during feeding. Twice per day feedings are recommended at room temperature for those who do something like a 1:1:1 (i.e., 1 part starter:1 part flour:1 part water by weight) or 1:2:2 feeding. You're doing something closer to 1:8:8, which means it will take longer for the yeast to process all the new flour and then for the bacteria to deal with those waste products. The only danger with such high dilution in young starters is that microorganisms actually present in the flour may still be able to overwhelm the things you want to grow and/or the starter may not be developing enough acidity by the end of your growth cycle to kill off those bad things.

Does your starter smell (or taste) acidic right before you feed it? (It doesn't have to be strongly acidic, but at least mildly so.) If so, I think your starter is likely very healthy and having youthful growth spurts.

In any case, I'd test it in a batch of dough before trying to diagnose further. In a worst case scenario, as long as you're getting some acidity before feeding (and not seeing mold, hooch, discoloration, or other weird things besides the odor), you should just keep feeding regularly, and it will likely sort itself out in a week or so.