The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

SD Yeast-What happens @93F

DanAyo's picture
DanAyo

SD Yeast-What happens @93F

I want to develop a starter that is high in LAB. My plan is to mix 100% starter using 25% whole rye and ferment it @ 93F.  My concern is how will that affect the yeast? 

Dan

DanAyo's picture
DanAyo

What will happen to the SD yeast if fermented at 93%? I read that 84F is optimum for max yeast. At 93F will they die, or quit multiplying or what?

Doc.Dough's picture
Doc.Dough

DBM has (for years) been telling everybody who will listen how to get a high LAB starter.

You can find it here

mikedilger's picture
mikedilger

In theory (in a simplistic theory):

S. cerevisiae will be fine and rather active (nearly at peak activity, it loves that temperature).  C. milleri will have only about 15% of it's peak activity.

If both yeasts are present and the dough was held at that temperature long enough, C. milleri would probably die way back, outcompeted by S. cerevisiae.

If S. cerevisiae wasn't present (some believe it doesn't survive well in sourdough environments), C. milleri would just chug along at 15%, so the LAB would significantly dominate the yeast.

In either case, you should still have plenty of active yeast of some sort or another.

There's no way to know without trying it, or getting a response from someone who has already tried it.

Doc.Dough's picture
Doc.Dough

Look at Rob Dunn's results (like actually look at the species they identified in the hundreds of starter samples from around the world).

mikedilger's picture
mikedilger

of Rob Dunn Lab's work. I appreciate the pointer. I'm aware S cerevisiae dominates most sourdoughs. From 1978 to 2016, C. milleri (later renamed C humilis, briefly Torulopsis humilis, later again Kazachstania humilis) was the 2nd most commonly identified yeast in papers on the subject (De Vuyst et.al. 2016). Yet it's far down the list in Rob Dunn's work, but at least still shows up as dominant in 3-4% of starters.

I don't know what kind of yeast dominates Danny's starter. Actually trying it is probably the only way for him to find the answer he seeks.

David R's picture
David R

I wonder if...

  • Starters have actually changed since the 70s
  • Earlier papers had small sample sizes
  • Earlier research was skewed or wrong
  • New research is skewed or wrong
  • Something else
Doc.Dough's picture
Doc.Dough

Just better analytical tools.

David R's picture
David R

Unless a person was everywhere at all times, changes in other countries would naturally go unnoticed. Incremental changes in one's own region are also hard to spot. But I'm certainly willing to agree with you anyway, because I think the idea that the research has changed while the biology has remained about the same makes the most sense.

mikedilger's picture
mikedilger

They are dimorphic, meaning they have two distinct phases that look very different. Often one yeast had two names because of the two phases. And until recently they were grouped according to morphological and physiological features, irrespective of DNA. That's why the names changed so many times.

Also, once Candida Milleri is identified by one scientist, subsequent scientists would have to buck orthodoxy to claim something different and nobody wants to look stupid or get their paper rejected.

I'm excited by the new research. Hopefully in the not to distant future we can figure out how to reliably create a particular sourdough starter with the particular variants of microorganisms we want.

Doc.Dough's picture
Doc.Dough

They have a lab where a few folks maintain their pure cultures and make up kits which they send out to their field bakeries once every X (maybe a couple of weeks) where they are propagated according to a specific discipline.  Small "artisan" bakeries don't do that (and thus risk having their culture drift) so that they are more dependent on cultures with long term stabilty (as well as good refresh discipline).

Mixing in large batches helps but the limit is contamination.  And that probably sets the frequency with which the central lab and corporate policy demand that the cultures be re-set to the current baseline.

That is most certainly how yogurt is made to be consistent. And if you have ever tried to maintain a yogurt culture derived from a commercial yogurt, you probably noticed that over time it drifted.  I think this is in large part because the results are more desireable when they use a known ratio of specific species which is not the same ratio that is stable.

mikedilger's picture
mikedilger

This is from Liz Landis, one of the team at Rob Dunn Lab: http://microbialfoods.org/yeast-profiles/

Doc.Dough's picture
Doc.Dough

Thanks for the link.  I have posted a question over there.

DanAyo's picture
DanAyo

From the links in this post It has become clear that starters vary a great deal. I think I understand now that to ask a specific question about an unknown starter is not answerable in specific terms.

When I read about specific yeast, some are more exciting than others. Here is my question. Let’s pretend I can acquire my dream starter. I was able to hand pick each and every species of yeast and LAB in this starter. It comes in  the mail and I start to feed it with my flour and water and setup a routine in my environment. Will this starter keep the original yeast and LAB, or will it become like every other starter that I’ve maintained in my house?

Aren’t the organisms in my flour transferred over to the starter?

Dan

David R's picture
David R

The government of Glonge sets up a colony on an uninhabited island. The colony is there for 200 years and thrives. They've had many children, and their population has grown to five thousand, but even though they have no laws about immigration, no immigration has followed the first colonists.

Then, suddenly, immigrants from Pavala begin arriving. A thousand in the first year, and another thousand Pavalan immigrants every year, for ten thousand years. No new people from Glonge show up though, even in all that time.

Everyone in this story has normal human lifespans. After the ten thousand years are up, do the island people look like they're from Glonge?

breadyandwaiting's picture
breadyandwaiting

This is what modern yeast-search can hopefully answer! Initially I thought the answer was "no way" (as in, the original starter would effectively be wiped out after a few weeks to months of feeding in a new environment) but I came across a blurb that seemed to suggest that at least certain elements had the ability to perpetuate even years later...  (Can't find it now, unfortunately.)

This would actually lend some credibility to the practice of chasing down particular starters, which to this point I thought was a relative waste of time... 

mikedilger's picture
mikedilger

It depends.  Here's my thinking on this:

The organisms in your starter have been selected via a process of natural selection that leaves behind the most vigorous organisms.

These superstar vigorous organisms sometimes have defensive chemicals as well, keeping out any competitors (acidity being the most obvious, but there are also 'killer yeast' and other chemicals in the literature).

The relevant organisms on the flour which can survive in the starter environment are in very minute quantities compared to the gigantic colony in your starter.

I suspect that with a healthy starter kept in a stable environment, the organisms in the flour cannot compete and die out every time.

However if the environment drifts the starter can drift.  If that environment becomes more favourable to a competitor present in the flour, then in a week or so that new organism will take over and a phase change event will take place, your starter rather suddenly being different [but not necessarily detectably so].

When you get a starter from someone else, it is very likely that the environment will change (different brand of flour, different minerals in the water, different feeding schedule, different temperature, etc).  That is IMHO the reason why starters tend to change when transferred between people.

It's not that flour-A will cause every starter fed it to drift over to population-A, but rather that environment-A selects for organisms that are optimised for environment-A.  And environment-A is effected by the organisms themselves (defensive chemicals, types of food left behind, etc). And hence the chaos of life.

To illustrate this point, one of my favourite recipes is a recipe for scorpions from antiquity. Take two bricks and a basil leaf, put the basil leaf between the bricks, put them in the hot sunshine, and in a few days you will have scorpions. People used to believe in spontaneous generation. Now we realise that environments select for the organisms that inhabit them.

As a data point: I have had two starters side-by-side fed the same food in the same manner and they did not converge, they kept their individual traits (at least for about a month, when I dried one and kept the faster of the two).

In summary: it's complicated

DanAyo's picture
DanAyo

I hear what you are saying Mike, BUT - that has not been my experience. I have had, probably 5 unique starters from 5 prominent bakers from various parts of the US. After feeding these starters that same as my “house brand” starter for a few weeks (on the counter), I am unable to distinguish one from the other. If I don’t mark them I can’t tell the difference for any comparison. That includes smell, taste, rise, flavor in bread, or rising power. I may not be right, but as far as I know this has been my experience. But I am forever willing to learn.

Have any other bakers had a different experience with dissimilar starter that are maintained identically?

Dan

mikedilger's picture
mikedilger

I can tell you more about my experience, but I'll refrain from making proclamations about what might be happening for the time being.

In my case the two starters were started in very similar ways on very similar foods in the same town, but by different people in different buildings.  Let's call them Nick (from the Cafe) and Campagne.  I started Campagne in January, and it was stable but slow.  I brought Nick home from the cafe which was started 6 months earlier, and he was very fast. Since Nick was already getting half-white-flour and half-whole-wheat flour, I thought it wasn't a huge change to just give nick the same flour that Campagne was eating (45% white from the same brand, 45% home ground wheat instead of Pam's, 10% rye which was quite new for Nick).  Since my farm runs on rainwater from the roof with both a bacterial load and low mineralisation I collected municipal water (pre-fluorodated but potable) in jars. I feed both starters on that water, which was new for Campagne.  I never used the same spoons or containers to avoid cross-contamination.

Over the 4 weeks or so that I kept feeding them in parallel, Nick maintained rapid activity (2x in about 6 hours, then collapsing) and Campagne maintained slow activity (2x in about 10 hours peaking about 2.5x and collapsing after about 13 hours).  I eventually tired of Campagne which was just way too slow so I dried it and put it away.

Maybe they would have converged if I did it longer.

Nick did change when he came home from the Cafe.  The smell changed.  But the activity didn't.

 

 

David R's picture
David R

Too bad that you never had the opportunity to address Campagne in a congratulatory tone, "There you are! Just in the time of Nick!" ?

David R's picture
David R

... unless one organism in your particular batch of flour is the proverbial (and figurative! ?) 800-pound gorilla, out-competing everything in its path.

Doc.Dough's picture
Doc.Dough

A thought piece and an associated figure to think about.

All curves are notional for purposes of illustration and do not represent lab results.

mikedilger's picture
mikedilger

This seems like a very reasonable model.

I have long considered the amount of potential competitors in flour to be minute in comparison, but I have just learned otherwise.

mikedilger's picture
mikedilger

I was under the impression that the LAB growth curve was steeper than that of yeast but lags more when cultures are fed, such that the yeast were favoured if you refreshed more often. I think I heard that from Teresa Greenway, not from a research paper.  I'd love to see research on that.

Doc.Dough's picture
Doc.Dough

My experience is that the LAB grow rapidly and acidify the batch slowing down and eventually ceasing reproduction when the pH reaches ~3.6 but (so long as nutrients are available) continuing to produce acid down to below pH 3.4 (species vary).  This means that you know when LAB population has peaked by watching the pH (pH<~3.6= no additional LAB population growth)

The yeast grows more slowly but basically ignores the pH, continuing to replicate until it has consumed the available nutrients.  So it is harder to tell when the population has peaked because you are trying to judge when replication rate equals death rate.

Amylase enzymes in the flour continue to break down damaged starch so that under some circumstances yeast growth and acid production can continue for extended periods of time (I have demonstrated TTA increases that continued for over 36 hrs at room temperature).

Doc.Dough's picture
Doc.Dough

There should be no lag phase if you feed at peak growth rate so the LAB can continue their rapid exponential growth without delay while the yeast just keeps plugging along. There is no lag phase because the biological mechanisms that are required to facilitate growth have already been built and are actively in use.

DanAyo's picture
DanAyo

Doc, the Starter Stability diagram has some super surprising information. It shows refreshing the starter early to increase the LAB. This is the exact opposite of what I thought.

Dan

Doc.Dough's picture
Doc.Dough

So don't use them to make decisions

To maximize LAB refresh on pH.
Or let it sit in the refrigerator until a lot of the yeast dies off.

dmsnyder's picture
dmsnyder

It is my understanding that, at any one time, a starter contains multiple varieties of both yeast and bacteria. Depending on the current environment, especially availability of sugars, hydration, temperature and pH, some set of organisms will be dominant numerically and will be metabolizing at some rate and by some pathway.

If any of the environmental variables change, the balance of organisms and/or their metabolism will also change. If you want a starter to maintain consistent performance, you need to maintain a consistent environment. If you want to change the starter's performance in some way, you can do so by manipulating the environmental variables. Ah, if only we understood the complex interactions among all the variables to really fine tune our starters' characteristics.

One other point: The constellation of environmental variables that maximize yeast or LAB division are not the same as those that maximize metabolism or production of every important metabolite. 

David

Doc.Dough's picture
Doc.Dough

I am patiently waiting for Rob Dunn and the folks associated with his lab to tease out some of the complexity buried in their data.  Since a substantial number of their original samples have common roots, it would seem logical to build a database of similarities among those known to be related and to find the samples that are measured to have high genetic similarity and test whether they share any common heritage.  But they are clearly starving for research resources to do that kind of thing but won't provide access to their data so that others can do it for them.  It is the starving grad student problem.