Can't get rid of alcohol smell in my sourdough starter

Question

I made my first sourdough starter around 3 weeks ago. I made it with spelt flour. It was nice and ready after a 7 or 10 days and had really nice yeast smell. I had to leave town for 4 days and let my husband take care of it. I instructed him to feed it twice a day with 1:1:1 ratio (as I did before, discarding also). First 2 days everythig was fine, then it startet to develop wine, alcoholic smell. What I think happened is that the starter became more active and hungrier so feedings from my husband weren't enough. As I came home, I startet feeding it more often with more food (around 1:4:4) and it didn't help. I tried more flour than water, white flour, mix of flours, nothings works. It doubles after several hours, gets thiner and smells. There is no hooch, but are lot of bubles. We have around 25°C in our home. I tried to put part of it in the fridge, it had slowed it down, but still had a little of alcohol smell after I took it out. I kept feeding it around 3 times a day with more food for around a week and nothing has changed. I just want to bring it back to balance, it to have proper yeast smell and store it in the fridge. Can anyone help? Thanks!

Answer 1

Interestingly, I think the extra feeds might be contributing.

So, there's two types of respiration in yeast: Aerobic, which needs oxygen, and produces CO2, and anaerobic, with a lack of air,which produces alcohol. Anaerobic is less efficient, and kicks in when there's no oxygen

The problem you're having is that, with the extra feeding, you're driving the yeast to grow very fast. Your kitchen is pretty warm, and so you've got pretty perfect yeast growing conditions.

Extra food really only drops the alcohol production because you're stirring it, and because the water added will contain some oxygen, and because you're diluting it down. However, a fast growing yeast culture will massively outstrip your ability to feed your way out of this.

I think you have a healthy starter, but if the alcohol smell is a problem, moving it to a cooler space would be my first call.

Answer 2

A bit of alcohol smell is normal as it's a natural byproduct of the fermentation process. After all, the whole point of feeding the yeast is so that it can convert the starch in the flours into carbon dioxide and alcohol. Even a powerful alcohol smell isn't necessarily an indicator of a problem as long as there isn't any hooch forming.

The smell you need to look out for is a vinegar smell, as that's an indicator that the yeast is starving and bacteria is starting to take over. At this point, you can try to do the split-and-feed technique or perhaps you could even "wash" the starter, but whether or not it's salvageable depends on how long it was neglected and the environment it was living in.

And needless to say, if there's mold, just throw it out. It's not worth risking your health just to save some moldy starter.