Hello,
I have been baking with commercial yeast for almost a month now, but want to branch out with sourdough. I started a small starter using the same amount of water and flour by weight (40g) and have been feeding it with the "standard schedule" : discarding half before every feeding. I now feed twice a day since yesterday (I'm on day 5) since it would develop hooch after about 10-11 hours. It's working fine so far, altough I doubt it will be ready for this weekend since it only smells of vinegar and there's no real rise (which isn't a problem, I'll just keep doing what I'm doing, bacteria is probably more prelavent than the yeast right now).
I come from a homebrewing background and thought about the way yeast propagation was done (i.e. on a stir plate). I still have my stir plate. Due to constant aeration/movement, yeast propagate a lot faster on such a setup than when undisturbed. I reasoned that yeast is yeast and would it be possible to use higher hydration and a stir bar (higher hydration since a stir plate won't readily turn a stiffer starter) to propagate a starter faster ? I've tried to find any info on this and have fallen short.
Only problem would be the ration of water to flour would be out of whack, but that could be modified once the starter is ready by incorporating more flour at that time.
Doc.Dough tells me he sometimes dilutes his starters with super high hydrations.
Tell me more about your stir plate. Is it spinning magnets that turn a metal bar in the solution
Can you keep the solution warmer? 82-84F
Danny
I agree with Danny, the stir-plate sounds like a great idea. I am quite intrigued!
There are no stupid questions. Just unasked questions.
You understand perfectly how to manage it. If you have a high accuracy scale (mg) you can track the conversion of sugars to CO2 which manifests as weight loss. My empirical tule is that starter is mature when it has lost weight equal to 2% of the weight of the flour you added when you fed it. If I feed at 3:13:16 (g) I can put it back in the refrigerator after it has lost 320mg.
Sadly my scale is not that precise, plus homebrewing is usually done with commercial yeast and not natural fermentation.
The need for propagation is because the commercial options sold to consumers, apart from the dry yeast packs, are usually not enough to insure correct and proper fermentation of 5 gallon batches at the usual gravities (sugar content, and thus alcohol potential). With beer yeast, there is a very real possibility of getting weird flavour profiles or stuck ferments because the yeast gradually die off once the alcohol content climbs if the populations aren't strong/hardy enough (dependant on strain though).
With a stir plate and commercial beer yeast, one stage of propagation would usually be enough for direct pitch afterward, and would usually be done in about 12-36 hours, provided sufficient yeast populations at the start and that temperatures weren't too cold.
Only problem that I might run into is that my beaker is pretty big (2L) and conical, so mixing flour and water might be a hassle... I would probably need to run something like 1:3 (flour/water). Could that pose a problem with propagation or throw the yeast/bacteria proportions out of balance ? I woudl probably "seed" with a small amount of commercial yeast at the beginning.
You said: "I would probably "seed" with a small amount of commercial yeast at the beginning. "
If you want to propagate commercial yeast, that is a very easy thing to do, and a large fraction of sourdough starters have saccharomyces cerevisiae as their dominant yeast (see Rob Dunn Lab) but don't contaminate your starter with commercial yeast. Not because you can't - you can, but the commercial strain will quickly dominate and you will then have to wait a number of generations to get your starter back in balance. You can start a starter with commercial yeast, but the purpose in doing that is to get enough CO2 into the mix early so that the carbonic acid it forms drops the pH to a point where the leuconostoc can't compete. You can do the same thing by adding some pineapple juice for the first couple of days (see Pineapple Juice Solution part 2). And when you initiate a starter with commercial yeast it still takes a long time to get a decent balance of yeast and LAB.
A fair number of people are just feeding their poolish from one day to the next waiting for yeast to re-appear in the grocery store. It works, though you might want to adjust the hydration a little.
It sounds like you have already started a starter and just need to build up the yeast.
and definitely worth a try. One thing to be careful of, though, is that high hydration and high temperature are a good incubator for lactic growth, so I would keep the temperature at 25C, max 28C.
Lance
see here at 5 minutes...
180% hydration IIRC!
This machine regulates a desired temperature and stirs continuously..
I am had the same question. I homebrew and have stir plates for brewer's yeast starters.
Curious if they can be used for sourdough starters. Seems workable, just would have to figure out the right mix.
A butter knife and 30 settings a couple times a day is all that's needed. And that includes cleanup. Enjoy!
I am sure Michael knows more about this, but somebody in Europe produces tons of dried starter which is added to dough that is otherwise dominated by commercial yeast. And the manufacturer of the starter will choose an operating point that maximizes yield against some cost function. I would not be surprised if it was done at high hydration then centrifuged to dewater it before a final drying step. In the land of good beer the opportunity for reuse of equipment and skills seems rich.