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For LAB to flourish must Yeast be present

DanAyo's picture
DanAyo

For LAB to flourish must Yeast be present

For LAB to flourish must Yeast be present?

Just today I read that 2 bakers had starters that were grossly overtaken by LAB. That made me wonder if some amount of Yeast were necessary for this to take place.

The gist of my concern
If a starter is overrun with LAB is it feasible to feed high ratios of starter to flour in order to re-establish a healthy balance. Or should the starter be thrown out and anew one started.

I appreciate your help.
Danny

The Great Answer - for those that have starters that have become extremely acidic and are wondering if they should start over and build a new on.
https://www.thefreshloaf.com/node/67921/lab-flourish-must-yeast-be-present#comment-4857
“ I'm sure it's easier to revive a starter than start a new one: even if it had no yeast left (highly unlikely IMO), at least the LABs will provide an acidic environment for the new yeast to start, and keep the bad guys at bay.

gavinc's picture
gavinc

My take on this:

Yeast and LABs have no direct relationship. However, when yeast consumes simple sugars, CO2 and alcohol are produced. When lactic acid or acetic acid encounter alcohol, esters are produced that result in the aromas.

I also note that when you want to store a starter in the refrigerator for a few weeks, you feed it and give it some bench time to give the yeast a head start before refrigeration or else the starter will be LAB dominant.

Cheers,

Gavin

 

DanAyo's picture
DanAyo

Gavin, “ I also note that when you want to store a starter in the refrigerator for a few weeks, you feed it and give it some bench time to give the yeast a head start before refrigeration or else the starter will be LAB dominant.

No science to bake this up, but it seems to work well for me. Keep in mind, my starter gets used often and is replaced every time a new dough is made. I ferment to refreshed starter to maturity. Then feed the matured starter a little extra flour without any added water. The idea is to provide fresh food and also to tighten the starter by a small amount. 

One other thing...
I have communicated with Debra about using a high protein flour for feeding starters. She advises all purpose. BUT, in this one case I went with my gut. I use super high protein flour because I want the gluten in the starter to be strong when introduced to the levain. May not make a huge difference, but it makes sense to me. Been doing that for quite a while and like the consistency of the starter when removed from the fridge. Liquidy, soupy starters don’t appeal to me.

gavinc's picture
gavinc

Hi Danny,

You may be onto something with the high gluten flour for feeding the starter but consider: I have a very strong rye sourdough that is 85% hydration. Whole rye grain flour is about 15% protein but is low in gluten. I make a liquid white flour levain over two feeds that is very vigorous using 11.5% protein white flour.

Cheers,

Gavin 

DanAyo's picture
DanAyo

I don’t understand your reply. The reason I use high gluten (in Italian flours - long fermenting) flour is because I want a flour that is strong enough to withstand the fermentation of the starter (also the long retardation for storage) without degrading the gluten. Also when I mention high gluten, I mean high quality protein that makes a strong dough. Definitely not grains like rye. My only use for rye in a starter is for the microbes that 100% extraction organic whole rye brings to a new or weak starter. But I rarely use it in my present culture.

Here is my current starter maintenance routine.

  • every week the starter is removed from the frig
  • some of the cold starter is removed and fed 1:1:1 with warmed (~105F) water
  • it ferments for 4hr @ 82F
  • once matured it is stirred down and enough flour is mixed in to tighten up the starter a bit - the idea here is to add a little extra feed for the 7 day retard and also to slightly reduce the hydration to provide extra strength.
  • after 7 days the process is repeated

Since I bake often the general procedure is to build the leaven in a single feed (from cold, using warmed water) and fermenting for 4 hr (or more if the feed ratio is higher than 1:1. Some of that levain is placed back into the fridge to perpetuate the culture.

After using this technique for quite some time, I am confident that it works for me.

BTW - the flour I like best for starter feeding is Caputo Americana. I’ve tried a great deal of other flours (including KA Sir Lancelot (super high gluten), but Americana is my favorite by a lot. Michael introduced me to it last year.

gavinc's picture
gavinc

Hi Danny,

I guess my point was that I don't use a high gluten flour in my starter but have a very strong culture. I note that your maintenance regimen is very different from mine and interesting. I've noted it for the future if needed. My rye sourdough culture is fed every morning and never refrigerated. I bake about 3 times per week.

Cheers,

Gavin

DanAyo's picture
DanAyo

Maybe I wasn’t clear Gavin. The strong flour has nothing to do with increasing the activity of the starter. The only consideration for using strong flour is to prevent as much gluten degradation as possible.

If increasing the activity was the goal, I’d use 100% Organic fresh milled Rye. That stuff always does the trick, IMO. If I were to build a new starter 100% Organic fresh milled Rye would be used. 

Doc.Dough's picture
Doc.Dough

My data shows pretty conclusively that you don't have to let it sit at room temperature at all before refrigeration.  Of course if you refrigerate at a temperature where the yeast is shut down and the LAB replicates, then the ratio of LAB:yeast rapidly climbs well above the 100:1 that is "normal" for a mature starter (though "normal" has a wide distirbution as well).  For the most part the yeast are not very pH sensitive while the LAB are quite sensitive.  There are also differences in sensitivity to lactate and acetate, and different preferences for sugars that they will ferment.

DanAyo's picture
DanAyo

Doc, how long should the culture be left @ 39F before it matures? Mine is always fed at least once a week or more. The current method I am using works outstanding for me. Like clockwork, a levain started with the culture taken right out of the fridge (1:1) using 100F water is matured in 4 hr @ 82F. I can set my watch by it. Been doing that for a couple of years now.

Doc.Dough's picture
Doc.Dough

If, by mature you mean the LAB:yeast = 100:1 then for a 1:1:1 mix it is probably around 7 days. But I am not convinced that 1:1:1 is the right mix.

Every bit of evidence I have indicates that the LAB have a higher growth rate than the yeast at every temperature until you reach the upper end of the viable range. The LAB grow faster and thus they grow first, but they eventually produce enough acid to drop the pH which slows them down and eventually stops their replication (around pH 3.8) but they continue to metabolize sugar and produce acid, they just don't replicate.

The yeast is slower, but insensitive to pH and thus grows exponentially until it exhausts the usable sugars. So the initial growth profile runs the LAB:yeast ratio up above 100:1, then the later log-phase yeast growth restores the 100:1 and if you let it continue past that point will further decrease the ratio. 

So there is an optimum where a starter should be fed, but a levain is not a starter.  So you don't care except that you want the right amount of acid and lots of yeast when you mix a batch of dough and you get to pick when you use the levain.  So levain is a bread design optimization problem and not a starter maintainence problem.

They are different problems and you need to treat them as different problems.

Ilya Flyamer's picture
Ilya Flyamer

Very interesting. I think I am starting to understand the idea behind multi-stage levain builds or starter refreshments before bake. For example, a higher ratio feed with a lot of pH buffering will let LABs outgrow yeast and accumulate flavour and acidity. And a small ratio feed after that won't let LABs grow much, but the yeast will continue growing.

Does that make sense?

Doc.Dough's picture
Doc.Dough

If you shorten the cycle just a little bit by feeding too soon and because of your schedule and feeding habit (say 1:1:1 and a cool growth period of 6 hrs followed by another feeding at the same ratio)  and you do that repeatedly for a large number of cycles, you wind up with lots of LAB and less yeast than you expect and you start to suffer from what appears to be under fermented dough. Or you feed it and put it directly into the refrigerator at 39°F where yeast grows more slowly than LAB and then try to use it before it has time to reach a new equilibrium that is close to 100:1 ratio of LAB to yeast.  All kinds of combinations and root causes put you in the same box of not enough yeast.  So periodically let your starter run to completion a few times {(1:2:3) + room temperature for 24 hrs will do it] then while it is not directly usable for a levain, it is a great place to initiate a cycle that will get fed, rested an appropriate period of time then refrigerated.

I worked hard to develop a routine that allows completion of the full cycle every time - thus my practice of feeding at 3:13:16 and waiting to refrigerate until it has lost 300mg of weight to CO2 (generally 10-12 hrs @ 80-84°F).  It is a cycle based on science (though the parameters were empirically derived) that produces very repeatable results.

DanAyo's picture
DanAyo

Doc, you wrote “ my practice of feeding at 3:13:16 and waiting to refrigerate until it has lost 300mg of weight to CO2 (generally 10-12 hrs @ 80-84°F)“.

I don’t doubt the statement above. Your approach is always scientific and therefore repeatedly measured. But your statement makes it apparent that the behaviors, characteristics, and activity of different starters vary considerably. I am unable to recall a single mature starter of mine that would continue maturing for 10-12 hr @82F at a feed ratio of ~1:5. Could it be our heat and humidity? What gives?

Back in December 2017, I documented a number of starter test attempting to extend the time to maturity to 12 hr. This was done at temps much lower than ~82F. No matter what was tried, including the addition of salt, all of the starters matured in considerably less time. They would completely collapse. I never was able to get a starter to ferment to maturity at warm temps for that duration. If I remember correctly my starters generally mature at 9hr when attempting to extend the duration.

This has been my experience for an estimated 20-30 starter in that time, maybe even more.

When I read that bakers claim to feed their starter every 24 hr at warmer than very cool temps, I am amazed and always wonder if this is so.

phaz's picture
phaz

Lab, doesn't require yeast. But it is kinda like a match made in heaven, both working together for the mutual benefit of the other. To much lab, or yeast, or anything else - the usual. Little starter, lots of food, a little warmth, some time and stirring. Let the critters work it out amongst themselves - they been doing it a long long time, no reason to think they won't now. Enjoy!

Ilya Flyamer's picture
Ilya Flyamer

Labs don't need yeast, see CLAS.

DanAyo's picture
DanAyo

I am wondering if a bread starter that has been allowed to grossly over ferment and become highly acidic still contains enough yeast to reinvigorate the starter. Or in extreme cases should that starter be tossed and a new one begun.

How should we advise a baker that post with this type of problem?

  1. rejuvenate the old
  2. start a new starter

It seems the best advice may be to do both.

Ilya Flyamer's picture
Ilya Flyamer

I don't know the answer, but I'm sure it's easier to revive a starter than start a new one: even if it had no yeast left (highly unlikely IMO), at least the LABs will provide an acidic environment for the new yeast to start, and keep the bad guys at bay.

DanAyo's picture
DanAyo

That is a stellar thought! Never considered that.

Even if the LAB only remain the starter has a great head start. My best advice then, would be to feed 100%Organic Whole Grain Rye. The starter should take off like a rocket...

merci

Ilya Flyamer's picture
Ilya Flyamer

Agreed! High ratio feed with whole rye should fix any problem I guess :)

Doc.Dough's picture
Doc.Dough

I have never understood the logic that drives some people to suggest that we "wash" the acid out of an old starter to rejuvinate it.  All you have to do is neutralize it.  And flour, especially whole grain flour, is a good buffer and will raise the pH instantly and hold it there until enough acid is produced to rebalance the mix.  A high ratio feed (1:7:7 is plenty high) will get you back up to a pH of 5.5 or higher which is optimum of the LAB and the yeast pretty much doesn't care. Then repeat that after the pH gets down to 3.8 again.  When I have refrigerated starter (32g size) that is over 3 weeks in the refrigerator I generally feed it twice before use, but at two weeks I just feed a new starter with a small bit of the old culture (3:13:16) and use the rest of the old culture to initiate a batch of bread (27:168:168 or larger if needed).

gavinc's picture
gavinc

Thanks, Doc. I have noted much of what you have said in your replies. Makes complete sense.

 

suave's picture
suave

Add a pinch* of yeast to the starter and it will right itself.

* it may take more than an actual pinch.

clazar123's picture
clazar123

There is plenty of dormant yeast present in any starter-it just needs activation. Introducing commercial yeast may get an active starter but it will be different. Dormant yeast just needs a little time and warmth to wake up. Whole grain is the favorite diet and will wake it up faster or add another population of the ubiquitous yeast.

HeiHei29er's picture
HeiHei29er

I always have a jar of raisin yeast water on hand in the refrigerator.  I refrigerate my starter (whole rye) and feed it once a week.  I've thought about using the yeast water in a starter refresh versus bottled water to help boost the yeast population.  Anyone ever tried that?  Good or bad experience doing it?  

DanAyo's picture
DanAyo

Interesting question, Troy. Hopefully Debra or Michael or someone with that type of experience will reply with an answer.

I do know that Lievito Madre can be started from a SD Starter or by using fruit or honey. But not sure this answers the question.

Benito's picture
Benito

Does anyone know if the natural yeast found on fruit that we use to make yeast water is the same yeast that live in our starters?  Are they acid tolerant yeast?

Ilya Flyamer's picture
Ilya Flyamer

No yeast is exactly the same as another, but yeah, it'll be acid tolerant. Fruit are quite sour on their own, and surely they survive when the fruit spoil too.

RainingTacco's picture
RainingTacco

You could write to these people:

http://robdunnlab.com/projects/sourdough/

Maybe they know something, or someone who took part in project used yeast water. 

leslieruf's picture
leslieruf

I guess I am thinking about those young starters that lack the strength to raise dough but are still active.  Often this is an imbalance with insufficient yeast present - do you know what I mean?   I think LAB can exist without yeast but a successful sourdough starter needs both in appropriate quantities.  

a belated addition - yeast water used to raise dough does not have the LAB if I have remembered correctly so yeast yes but I don’t know if it is the same yeast as you get in. SD starter 

Doc.Dough's picture
Doc.Dough

All LAB and no yeast to speak of in either case.

qed