The Fresh Loaf

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Mythbusters - Grain Yeast or Air Yeast?

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ElPanadero's picture
ElPanadero

Mythbusters - Grain Yeast or Air Yeast?

There has been a lively debate on other threads with varying views on whether the process of creating of a new Sourdough Starter is taking primarily, yeasts and LABs from the flour itself or from the air in your kitchen/environment.

At present I am firmly in the camp that supports the grain organisms, and whilst I accept there are all matter of yeasts, bacteria and particles in the air, I don't believe they contribute in any significant way to the initial creation of a starter.

To determine the truth I have begun an experiment.  In this experiment I have set up 2 separate mixes of flour and water.  One will be kept in a sealed small jar, the other will kept in a wide open bowl exposed to the air.  The latter will use what I am going to call "dead flour".  To explain:

I have taken equal amouts of rye flour (freshly ground), A and B.   Flour A I have dry fried at high temperature in a saucepan for a few minutes whilst stirring well.  For good measure I then microwaved it for 1 minute.  My intention here is to kill any and all naturally occuring yeasts and bacteria in the flour itself.   I then mixed this "dead flour" with a little water to make a pastey mix, placed in a bowl and will now leave it open to the air.  I will be stirring it regularly and adding nothing to it except a little more water if it shows signs of drying out.

As you can see I am giving the "Air" starter every chance by leaving it exposed next to my grain mill.  My kitchen ought to have far more airborne flour particles than most kitchens as the mill kicks out plenty of dust.

The second candidate, the "Grain Starter" I simply took freshly milled rye flour and water and mixed to the same pastey level and placed in a small kilner jar which I have now sealed with its screw top.

 

I will NOT be feeding either starter.  I will simply leave them as they are and see if either will develop any activity in the following days.  I will update this thread with results accordingly as time passes.  If it becomes necessary, i.e. if neither starter shows any sign of activity, I will start feeding with the same the usual quantites of dead flour / live flour and water.

A possible flaw in this experiment is that the "dead flour" in which I hope to have killed the yeasts and LABs may not now constitute "food" in the normal sense having been heated, though I am hopeful that it is still fine.   If anyone believes it won't be able to be fed upon by any airborne yeasts then do let me know.

UPDATE Sun 23rd Feb

It is now 2-3 days into the experiment.  Neither starter has been fed at all since the first day.  The "Air Starter" has been stirred regularly and left cited by the grain mill.  The grain mill has been used throwing out plenty of grain dust.  Nevertheless, the air starter shows absolutely no signs at all of activity, no bubbles, no change in volume.  It looks like this:

The "Grain starter" on the other hand shows significant signs of activity and has risen within the jar as can be seen below:

Both starters have been left at the same room temperature, neither have been fed, both have been stirred, nothing more.

I suspect that in the next 2 days the Grain starter will have risen even more.

 

mwilson's picture
mwilson

All the sporulating organisms that were present in the flour before the heat treatment will now have the best chance.

I predict mould growth on the air exposed starter made with flour A.

I would also be wary of mould growth on the starter in the jar. If the lid is tight fitting, the air gap between the starter and the lid will become humid and encourage mould growth. For this scenario you would have been better to make a firm dough, wrap it and tie it as per our discussions of Italian SD maintenance. I have started a starter this way no problems which proves the point you're trying to make.

ElPanadero's picture
ElPanadero

Michael.  Bear in mind I'm not trying to make a viable SD starter here.  I'm simply trying to prove whether or not starters are in any shape or form created "out of thin air" so to speak, which I don't believe for a second.  The "grain starter" will have a very small space for gas to escape should any build up.

suave's picture
suave

It has been shown time and again that the primary initial source of sourdough microflora is the flour.

ElPanadero's picture
ElPanadero

but there are some among the forum that are still on the fence on that issue.  An experiment like this might help them make a more informed view.

MisterTT's picture
MisterTT

been better to irradiate the flour.

dabrownman's picture
dabrownman

another example to counteract the mold factor.  Use a  Mini Oven Method!  Take 2 walnut sized pieces if 66% hydration whoie wheat.  One from a batch of sterilized whole wheat and water and one from a batch of non sterilized whole wheat but sterilized water.  Get 2 paper bags and place the one that has non sterilized whole wheat in a bed of non sterilized flour in one bag and completely cover.  Place the sterilized one in sterilized flour and completely cover in the other bag.  Seal end of he bags and put on top of the fridge for 7 days and forget about them.  In 7 days, when the insides are scraped and used as a starter for a levain build for both,  one will be a starter and the other will not.  I only did half the experiment using unsterilized whole wheatbut, as always,  Mini was right I got a nice starter with my experiment.

ElPanadero's picture
ElPanadero

I'm not trying to create any starters here.  I will be throwing both away as I already have 2 active starters.  I just want to demonstrate whether or not you can get a starter going from just the particles in the air, which I seriously doubt, but we'll see.

chris319's picture
chris319

Maybe steam the flour in a makeshift DIY autoclave? It might turn to goo but would be fun to try.

WoodenSpoon's picture
WoodenSpoon

From what I read on that other recent thread I don't think that even photographic evidence of the results will convince those still on the fence.

ElPanadero's picture
ElPanadero

You may well be right.  Nevertheless, for my part, despite what I have read and experienced myself, I am still willing to make the effort of a practical experiment to demonstrate the truth either way.  It hopefully shows respect and benefit of the doubt to those with contrarian viewpoints.  Who knows, the "Air starter" might suddenly take off in which case they will have a case.

placebo's picture
placebo

The problem is you don't know if you managed to kill off everything in the heated flour. You need a control, the supposedly sterilized flour in a sealed container. And even if the unexpected should happen, you won't know if it was just a fluke. You'll have to repeat the experiment and see if you can reproduce the results predictably. If that happens, then they might have a case.

dabrownman's picture
dabrownman

into amobile app and game.  LAB &Yeast & LAB & Yeast &........:-)

chris319's picture
chris319

Forget steaming the flour.

It absorbs too much mositure.

tea berries's picture
tea berries

and I'm curious to see how it turns out. As a newbie myself, something like this really helps for the future starters I make and certainly supports money well spent on flours that are as organic and raw as natural since they should retain and support the healthiest amount of micro organisms. 

Antilope's picture
Antilope

It is in the flour, but how does it get there?

At the beginning of the growing season you have a plowed field full of planted wheat kernels. Were do the wild yeast and lactobacillus come from? It must be the soil, is there any other source for miles around? It must be blown up from the soil onto the wheat kernels throughout the year. This is then ground into the flour when the wheat kernels are harvested. 

So, the wild yeast spores and dried lactobacillus must be airborne at some point. Not in your kitchen, obliviously, but in an outdoor environment, there must be free ranging, airborne yeast spores and lactobacillus, to some extent. Or maybe it's spread by insects from the soil to the wheat kernels, or maybe some combination?

mwilson's picture
mwilson

you're a step away from a philosophical discussion. If in the soil, where did it come from, if in the air how did it get there? Where does any living thing originate from..?!

Antilope's picture
Antilope

Sourdough cultures didn't just spring out of a petri dish in the kitchen and start a symbiosis. This is not its natural environment were it reproduces, spreads, thrives and evolves. It also doesn't do that in flour out in nature. Flour is a product of man. The wild yeast and lactobacillus must thrive and create their symbiosis somewhere in the outdoor environment. They didn't just start this relationship when man ground wheat kernels to flour and added water. Maybe it starts in puddles in the fields? In the soil. Smashed kernels laying in the soil, with other decaying plant material. That's were the magic started. That's where spores spread from, up to the wheat kernels in the field. If the wheat wasn't harvested, like wild grasses are not, the kernel falls back into the soil and the cycle starts all over again. 

What covered the wheat fields before wheat was planted? Prairie Grass. For hundreds of thousand of years prairie grass covered the plains. That's probably where the sourdough wild yeast and lactobacillus symbiosis began, in and around the prairie grass.

mwilson's picture
mwilson

This is not its natural environment were it reproduces, spreads, thrives and evolves

Well, yes it is actually...

I believe you're looking at things the wrong way. Organism don't live for symbiosis, they live to survive. That goes for every living thing in this world. The symbiosis to which you refer is unique to the SD environment. And as I said before l.sanfrancicensis has never been isolated from any other source but sourdough and there is developing evidence to suggest it comes from us humans.

dabrownman's picture
dabrownman

2 membranes that causes a very energetic big bang, eventually the 4 forces of nature and a huge pile of hydrogen?   Or maybe an intelligent designer who made it happen as one of their tiny lab experiments to see where membranes and big bangs come from?  I'm personally blaming Lucy:-)

mwilson's picture
mwilson

I've always liked your sense of humour :)

ElPanadero's picture
ElPanadero

Whilst what you say is true, it has no meaning to the debate on whether or not it is possible to stand in your kitchen with a bowl of flour and water in your hands gently mixing away hoping to "catch" the wild yeasts in the air. I maintain that the idea is at best romanticism and most likely complete baloney, unless ones kitchen happens to be cited in a grain mill or in the middles of a grain field !

This myth needs busting once and for all because it clearly confuses newbies.

Antilope's picture
Antilope

The chances of capturing airborne wild yeast in your kitchen are slim to none. You are more likely to capture some commercial yeast that's in the dust in your kitchen. 

Xenophon's picture
Xenophon

But, pour la petite histoire and although this has nothing to do with bread:  in the city I hail from they produce a fruit beer called kriekenlambiek.  It's been produced for centuries in Brussels and the Brussels area with locally grown fruits, fermenting in open basins and has a very unique taste.  The brewers always contended that it was something 'in the air' which created the unique taste, even before anything was known about yeasts.

Centuries go by, production needs to be ramped up, the original variety of sour cherry used to make it becomes rare and imported sour cherries are used--> same result.

Then, one of the producers decides to shift locations because, well, it's not really handy to make artisanal beer like that in the middle of a capital city.  Spectacular fail.  They tried everything:  starting fermentation with a batch from their original location etc--> worked in the beginning, then the taste started drifting off.  After a lot of research it turned out that 2 yeasts which for some reason  naturally occur in the Brussels region but no where else are mainly responsible for fermentation and the specific taste.  For the beers: http://en.wikipedia.org/wiki/Kriek_lambic

So I guess there might be something in the air after all.  But we'll see how this turns out.

bread.on.beard's picture
bread.on.beard

Does anyone have the book titled World Sourdoughs from Antiquity by Ed Wood?  I don't have the book, but I recall a passage about his going to Egypt where he says (as I remember) he "captured" some airborne Egyptian wild yeast next to an ancient bakery discovered by archeologists that was located very near the pyramids?  Did he not sterilize some local Egyptian wheat, or some other ancient strain of wheat, to use as the host for his local airborne wild yeast?

Also, if his sterilized wheat had no living yeast in it, and he was able "capture" some wild yeast from the air, is it not possible that the wild yeast he captured could have blown in from anywhere?  It seems like on any given day, he could have captured any number of varieties of wild yeast  in his "culture jar," and eventually one variety would become dominate on one day, and possibly another variety could become dominate on a different day.  

And, if there are no living yeast in a sterilized batch of wheat, or flour, what is there to stop airborne wild yeast from "moving in?" 

Antilope's picture
Antilope

He had some flour sterilized in the U.S. and shipped to Egypt so he could capture whatever cultures were in the area of Egypt he was studying. 

Antilope's picture
Antilope

He had some flour sterilized in the U.S. and shipped to Egypt so he could capture whatever cultures were in the area of Egypt he was studying. 

suave's picture
suave

Keep in mind that Wood's book is mostly a vehicle for promotion of his "regional" sourdoughs.

chris319's picture
chris319

The irony is, yeast isn't what gives sourdough its flavor, so ... ? C.humilis is C.humilis be it in Egypt, San Francisco, Sao Paulo, wherever.

When I lived in San Francisco I used to see these and laugh:

http://www.fogtastic.com/

http://crapsouvenirs.com/25538/

They should put "Now with L.sanfranciscensis!" on the label. It would sell like hotcakes to sourdough bakers.

 

bread.on.beard's picture
bread.on.beard

Were you able to capture, can, and sell any wild fog?

mwilson's picture
mwilson

Depends what do you mean when you say "flavor".. If you mean acid then that's true. Yeast doesn't contribute any significant acid. But poor old yeast has a reputation of being cast off as gas producer only. Yeast and LAB together both play big roles in producing volatile aroma compounds.


How I define things:

Taste - perceptions on the tongue and mouth-feel
Aroma - perception of smell in the nose
Flavour - perceptions of taste and aroma combined.

 

Mike Jordan's picture
Mike Jordan

The way I see it (and I'm in neither camp) is that you invalidated the experiment by "killing" the flour if you were trying to determine if at any time in history yeast was obtained from the air rather than just the flour. In a normal and natural creation of dough, nobody starts with "dead" flour. Or sterile water or a sterile container.  The question really isn't if yeast from the air contributes to the the forming of yeast in the dough, but how much does it contribute and is it enough to make a difference.  Also, if you want to get really technical about it, there is probably more yeast in the air during the summer months, particularly when crops and natural vegetation are in bloom or ripe. I suspect there is a lot more yeast in the air during harvest time. As mentioned above, mold will probably get a foot hold before any yeast will.

Mike

placebo's picture
placebo

The way I see it (and I'm in neither camp) is that you invalidated the experiment by "killing" the flour if you were trying to determine if at any time in history yeast was obtained from the air rather than just the flour.

The claim is that when creating a new starter, you must leave it in an area exposed to the environment to capture yeast from the air. EP is attempting to show this is not the case because the yeast is already present in the flour.

 

adri's picture
adri

I like the experiment

One concern I really have is, that the "killed" flour also is really dead including enzymes. As to "Handbuch Sauerteig" (The german sourdough bible, a scientific book that summarises the research about sourdough) the provision of lower molecular proteins is of mayor importance. Therefore they depend on the amylase (micorbial and the one already in the cereal). (The book has great charts of enzymatic activity depending on temperatures, ph-levels, ... and charts of which lower molecular cabs / sugars are mainly produced).

I'm not sure how much food the microorganisms can produce on their own and how much they depend on the already existing amylases? I think it is time to conduct a test on my own: I'll create a seeded starter with pure starch and one with white flour. :)

Another type of starter that usually is created in a sealed environment is "lievito madre". But it uses honey as ingredient that definitely brings a lot of yeast (if you don't buy the pasteurised stuff).

Adrian

andychrist's picture
andychrist

One summer day a couple of decades ago, the NYTimes published a little piece in their Foods section about how to create a SD starter by "capturing wild yeast" by such a method, though they did not designate it "lievito madre." Anyway, as a right thinking New Yorker who always did anything the Times told me to, I dutifully followed their instructions, by mixing one cup of water with one of non-bleached AP and a tablespoon or two of local honey, covering the bowl with damp cheese cloth, and setting it in a warm but shady place outdoors to "capture" the yeast.  Late that afternoon I stirred up the contents and they roiled up out of the bowl. Unfortunately that's all I remember, no recollection of whether I was successful baking anything with that starter.

Mini Oven's picture
Mini Oven

I added local honey to feed my yeast water.  It took off.  That was a while back but I believe I still have a picture of it here on file.  anyway...

The comment of   "Yeast not contributing anything to the acid profile of the starter"   is something I have to disagree with.  I think it makes a great contribution.  I think the bacteria lower pH but if you have a certain group of them taking over the starter, they can make it very difficult to get the pH low enough to get the proper sd yeasts going.  

There are so many varieties in the starter and some might be better at maintaining more neutral pH.  How do you explain starters that have great flavour and almost no yeast?  

I finally got my low yeast starter converted but not without drastic interference to upset the established balance and maintenance of that particular starter.  Now that I got yeast thriving in it, the starter can lower the pH to maintain itself and return to the same maintenance pattern.  Patience is key. 

The starter just has to be left alone long enough for other bacteria and/or yeast varieties to get a foothold.  It's the only positive thing I can think of that supports acid rain in nature.  Minerals can also leak acids into soil or mud puddles.  The nature of the connection is to attack and decompose, returning organic matter back to matter.  

Yes, flour doesn't exist milled in nature or in the field, the growing bacteria and yeasts are not dumped with flour at the rate we feed them but there are a large variety of them to deal with the availability of food.  And they seem to adapt quite quickly to narrowed circumstances.  It's done on a minute scale in nature but everywhere.   We concentrate the process in our starter jars slowly building their numbers to be usable.  We also are determined not to let them rest.  Some more than others.

adri's picture
adri

I now made the following experiment:

10g of starter, directly from the fridge

20g of water

20g of either starch or wheat flour

I put it in a warm place and report back.

I know that the experiment has it's flaws: In starch there is less protein than in your dead flour and the MOs might need that protein. Therefore: If there is much less activity in the starch glass, it doesn't prove nothing. Just if the activity also is high, it is an indication, that my concern about your experiment isn't valid.

Adrian

adri's picture
adri

After 2 hours I know the following:

  • My starter is amazing, look at the rise just 2 hours after feeding
  • My permanent marker is crap
  • You don't see any bubbles in the starch mix
  • There must have been a lot of fermentation in the starch mix, as there was a "plopp" opening the jar. (as there was with the wheat-mix)


I now will feed a new starter with  a part of the starch-mix, to see, if it just cannot hold the gas or if it really didn't ferment well.

Adrian

ElPanadero's picture
ElPanadero

I'm not undrstanding your experiment but that's likely my lack of knowledge of what starch is, so by all means educate me. The primary "concern" in my own experiment is in providing a food source that is viable but which has no natutal yeats or bacteria in it (hence the dry frying and microwaving).

Does your starch not contain wild yeasts and LABs? How can you tell?

adri's picture
adri

As I seed with a quite potent starter, we can neglect any other microorganisms present.

I chose starch as it has a) a lot to eat in principle but b) no or almost no enzymes that break down the starch to chunks the microorganisms can digest. In theory, the microorganisms can produce their own enzymes to break down the starch.

I wanted to test, how important the role of the enzymes already present in the flour still is, as killing the enzymes is definitely something you'll have done with your dead flour.

Mini Oven's picture
Mini Oven

in the sourdough patent data... the  bacteria and yeast cultures were grown in an autoclaved soup.  Have to go back and find the temp and pressure but it might have denatured the enzymes as well.  

Adri, you forgot a "control"  just starter + water in a jar.  Otherwise I could claim the agitation or the water caused the starter respiration.    Yeast and micro organisms eat carbohydrates.  (That is the whole basis of feeding darm/gut flora with resistant starch to keep them healthy.  

My worry is that when I get a bag of imported flour that has been radiated, nothing will start up in it.  Maint. flour sure but not start up in it.  Want to see if your starch can start a starter?  Your evidence of gas in the starch jar, proves it is fermenting, just not getting trapped in the mixture.  What do you think of balloons for lids?  or baggies?

adri's picture
adri

Yes, it was fermenting. But much less than the one with flour as the 2nd step showed.

If you argue, that it the gas came from the agitation and rest fermenation of the starter, you would make my case ;)

The jar with flour was the control.

Mini Oven's picture
Mini Oven

Not without a way to measure the gas formed in both jars and compare them.  The gas escaped from the starch jar so it was not measured.  You cannot prove one had more gas than the other.  

A jar with just water and starter would also produce gas until all the beasties stopped using up the rest flour in the starter. So...  

adri's picture
adri

I'm not trying to prove this. I'm going by activity when used again as a seed. Did you read "The next step"?

Mini Oven's picture
Mini Oven

in the first jar.

ccsdg's picture
ccsdg

You do have an amazing starter! I'd suspect a lack of gluten in the starch. Not sure what you could do from here to disprove a null hypothesis.

adri's picture
adri

Me too.

As I suspected the lack of gluten in the starch, I conducted another test. I used the two starters as a seed for starters that definitely have gluten in them.

adri's picture
adri

The next step:

I discarded 30g in each jar and fed it with 20g water and 20g flour.

After 1.5 hours:

  • The wheat seeded mix more than trippled (rise >200%)
  • The starch seeded mix had some activity but the rise was just about 15% to 20% (it's difficult to see on the foto as there was dough on the inside wall)

I therefore conclude for myself:

  • I believe that the cereal own amylase plays an important role.
  • I cannot be sure. Further testing should be: Same test but with "killed" flour instead of starch.

I still believe, you don't collect the Microorganisms from the air but from the grains.

A side note: The fantastic rise of the wheat starter wouldn't have happened at room temperature. Both jars were in my incubator at temperatures above 30 degrees (above 86F).

Adrian, having Sourdough-Pancakes for lunch now :D :D :D

chris319's picture
chris319

There are so many varieties in the starter and some might be better at maintaining more neutral pH.  How do you explain starters that have great flavour and almost no yeast?

Mini and others who are interested, you should really plunk down and get a pH meter. You will love it. I used mine to determine the amount of acid to add to my sourdough water. Now that I know how much to add, I don't need to use it every time I bake. Here is what I have. Be SURE to get some calibration solution if you get one.

Here is what I have: http://www.amazon.com/gp/product/B005H78ZI0/ref=oh_details_o02_s00_i00?ie=UTF8&psc=1

http://www.amazon.com/gp/product/B001D0CKYK/ref=oh_details_o02_s00_i01?ie=UTF8&psc=1

Antilope's picture
Antilope

I'm going to get a PH meter. At what PH range should a starter be kept?

Here's an interesting list of various food PH from the FDA:

Approximate pH of Foods and Food Products

http://www.foodscience.caes.uga.edu/extension/documents/fdaapproximatephoffoodslacf-phs.pdf

chris319's picture
chris319

I'm working from memory here. Doesn't Debra shoot for a pH of 3.5? IIRC the patent discussed in another thread specifies 5. I shoot for 5.5 based on the ganzle study modeling microorganism growth.

dabrownman's picture
dabrownman

changes with time and feeding.  A Type 1 SD starter that is recently fed on a 24 hour schedule will start out at around 6 and end up at 3.5 pH  24 hours later - right before it is fed again.  The best pH for LAB is 5.5 and anything around 4-5 to 5.5 is pretty ideal for them  Les than 4.5 an LAB reproduction falls of more than yeast does.  A type 2 SD starts at 3.5 and goes lower but most folks at home don't keep these kinds of starters - more useful for big commercial bakeries that make tons of bread a day. 

Happy metering

ElPanadero's picture
ElPanadero

I have updated the original post above with progress

ccsdg's picture
ccsdg

Woohoo! As difficult as it might be to control confounds, this looks to be at least convincing.

chris319's picture
chris319

This from U.S. patent #3734743:

During make-up of the liquid starter of the invention, it is preferable to adjust the pH to about 5. For this purpose one may use acetic, lactic, hydrochloric, or any other non-toxic acid. This lowering of the pH has the desirable effect of suppressing growth of any adventitious microorganisms which may be present in the make-up materials, for example, the flour. The low pH, however, has little or no adverse effect on the growth of the desirable organisms, the sour dough yeast and bacteria, since these can proliferate in media having pHs well below 5. It may be noted that where the liquid starter is made up with previously developed liquid starter as the inoculum, the pH will be close to 5, and hence acid need not be added.

I'm going to get a PH meter. At what PH range should a starter be kept?

I find a medicine dropper very handy for adding acid by the drop -- I picked up a plastic one for babies at a supermarket pharmacy. I use lemon juice because I read somewhere, maybe in that patent, that acetic acid messes with the proliferation of the lactobacillus, so I don't use vinegar as the acid. You will find that a little acid goes a long way. Measuring by drops is easy to measure and reproduce. I don't manipulate the pH of my starter but do manipulate the pH of the dough, adding 3 drops of lemon juice to the 1/3 cup of water I use for my small boules. If I'm making a new starter, I let the pH fall where it may. The leucs will come and go, no big deal.

Also this from the patent:

An important ingredient in the liquid starter is salt (NaCl) which we found has the critical effect of maintaining the yeast and bacteria growth rates in the proper relationship. Because the starter of the invention contains a much higher proportion of water than the conventional sponge, there is a tendency for bacterial growth to outstrip yeast growth. The addition of salt counteracts this tendency by preferentially accelerating yeast growth. To attain this desirable effect when the liquid starter of the invention is made up, one includes about 1 to 3% of salt, based on the amount of flour.