Sourdough Starter - Yeast overgrowth problem
about two months ago I decided to convert my liquid starter to a dough starter following these instructions. I have waited for 2 weeks - waiting the starter to "transform itself into a pasty, gelatenous substance" - before I refed it. That pasty, gelatenous state never happened. The surface of the starter dried out and made a crust with a soft core. Of course I had it in a covered container in the fridge at 5.5°C.
The third week, it started to smell like the way commercial yeast tastes (since commercial yeast has no smell that I know of), but it was that yeast smell which you immediately recognize. The smell rang a few bells for me so I decided to take some of the dough from the bread-dough I was proofing in the fridge (made with the original healthy liquid starter) and start a liquid starter again. It turned out to have yeast overgrowth as well (the starter, not the proofing dough)
So it has passed roughly a month since the problem has started and so far nothing seem to work. There is always a layer of yeast waiting for me which looks sort of like wrinkled curtain on my liquid starter and like white patches/dots on the dough starter. I tried:
- (I did this 3 times and stopped because it had no effect) carefully scooping off the top layer, saving about a tablespoon of starter, washing the utensil with burning-hot water (but not boiling), and then putting the saved amount back into the cleansed utensil. Then I followed instructions on this webpage for "polluted starter" which work extremely well to get a vibrant starter but does nothing for the yeast problem. Here is the quote of instructions for your convenience:
"1. Using 1 of the 2 tablespoons you rescued from the polluted starter, add 1 cup of 75[°F] degrees water, 1 1/2 cups all-purpose white flour, and proof for exactly 24 hours at 72-77 degrees.
2. Refrigerate for no less than 12 hours, then repeat step 1.
3. The proof-refrigerate cycle should be repeated at least once. Use
your own judgement. If the starter was unusually dark or contained
mold, I'd suggest doing it at least 4 or 5 times to be sure the
offending organisms are eradicated. If the starter merely contained
other baking ingredients, then a single 24-hour proof is probably
enough. Each cycle is started by using 1 tablespoon from the last
- then I tried starving it, thinking the yeast might die off since it wouldn't have any food to feed on. I should mention that when I said "starve" I meant waiting a day or two after a collapse. It didn't change anything. Maybe I wasn't persistent enough but I just didn't dare to starve it longer. Somehow I thought neglecting it would make its health worse. Neglecting would be just waiting for sour smell (which I bet would never come).
So that's basically what I have been doing up to this point. It's better than what I started on but that's only because the original strain has been diluted so much (notice the above 1tbs method....1tbs in 2.5 cups of dough is diluting). When I say better I mean "the layer isn't as thick" and "the patches aren't as large/thick". The yeast layer, smell etc is still there. Help?