Starter - Relative Microbe Populations
The world is filled with wrong thinking. No matter how strongly or confident one is about a perceived fact, if it is wrong, IT IS WRONG.
Is it possible to maintain a starter in such a way as to greatly alter the ratio of yeast (fungi) to LAB (bacteria)? The question deals not with the production of CO2, acids, or other byproducts, but with the various populations of the 2 mentioned microbes.
Until recently I assumed that a starter could be managed (through food, temperature, and hydration) to increase the ratio of yeast microbes over the LAB microbes. Recently obtained new information from a trusted friend puts that thought in serious question.
Why does the answer to this question matter?
- If the relative population ratio of each set of microbes remain basically unchanged, then our focus is best targeted towards the byproducts produced by the two main groups of microbes.
- If we can swing the relative population ratio of each set of microbes our focus may be to prepare an environment that causes one group of microbes to multiply at a faster rate relative to other.
IF #1 is true, it seems that we can alter our starters characteristics rather quickly.
- I have long believed that a non-acidic starter can produce sour tasting bread, by simply providing the proper environment during the bulk ferment. Think about this. We know we can allow our starter to over ferment. And if we do, the starter will be extremely acidic in short amount of time and also in a single feed. Isn’t a levain just a big starter?
- If the relative microbe reproduction of both groups are of no consequence, then our focus is bested targeted towards enabling or hindering the metabolism(s) of one or both groups of microbes. For example - as the metabolism of the yeast increase, so does the production of CO2 and other byproducts.
We are fortunate to have a number of scientifically trained bakers on this forum, of which I am NOT one. My brain is untrained, but at times my mind takes me to deep places :-)
*NOTE - the word relative is used because the ratio of yeast to LAB greatly favors the latter.
- A thought for those that have not considered this
We are taught that once the starter’s PH drops to a certain level that the LAB are no longer able to reproduce. BUT the yeast are not negatively affected and continue to multiply. I used to wonder, if this is true how does the starter continue to grow much more acidic. The answer - even though they don’t multiply their population, the LAB continue to produce acids.
If the paragraph above is true, then doesn’t that prove that the population of yeast microbes can increase their population relative to the LAB?
I am thinking out loud and hope to learn from the replies to this post.
So too is the final dough!
Very good point, Abe!
I am sure the relative amounts of yeast vs LABs can be affected, although I haven't checked the literature. But, as you mention, they are affected deferentially by acidity. They are of course deferentially affected by temperature too! I guess you can eliminate the yeast if you culture at 40C, that's how you create a CLAS starter. So surely the yeast would be inhibited, but still growing, at temperatures a little below 40C. And there must be a myriad other conditions we can change that would, maybe slightly, but change the relative fitness of two populations. How about adding salt? Who would that favour? And at what concentrations? Or sugar? Or different hydration? Just how efficiently all of this works - well, that's a different question, and one would need to do some scientific tests to check that. Maybe all effects that don't kill the whole ecosystem are only subtle. Need to check the literature... Maybe Doc has looked into that already?
There’s a scientific article about a study of the influence of these three factors on LAB:yeast ratios. Here’s the abstract:
The authors reported a 20:1 ratio of LAB:yeast at the beginning of fermentation. With higher salt concentrations, the ratio was found to reach 1:1.Interesting... Wish I had a stable and well established starter...
I'm about a month into my first starter and still getting it figured out. So, I don't have any solid history to determine if there are any effects from the switch.
We're having a water softener installed tomorrow. It won't be a significant change, but adding it will increase the Na content in my water by about 0.05%.
Fortunately, I'm at the point on the learning curve where I still don't know what I don't know, so if there is a change, it won't be anything I'll recognize or worry about. :-)
"We're having a water softener installed tomorrow. It won't be a significant change, ...."
Heh, heh. I would bet that it will be a significant change.
Depending on what other filtering mechanisms are installed along with your softener, you may or may not benefit from a "bypass faucet" installed at your kitchen sink.
"Softened" water is a weird animal. There are new ways of doing it. Depending on how it is done, you may, or may not, want to drink it and cook with it.
Hopefully, your contractor will carefully explain the options that they have available, and what is optimum for drinking and cooking.
Is better for suited for bread making. Here is an article from KA.
We’re about 250 ppm. Will leave a by-pass tap and blend the two 50:50. Should be a happy medium...
Thanks for the heads up!
Please report back. I too have a water softener but over the five years that I have been making bread, I have only used bottled spring water to feed my starter and make bread. I'm curious to hear your results.
Harder is generally better than softer when it comes to fermentation. But the extremes of each can both be problematic.
Thank you for sharing this, perfect paper for the question!
“ If the paragraph above is true, then doesn’t that prove that the population of yeast microbes can increase their population relative to the LAB?”
I’m not so sure. I don’t haven’t read any studies that would support this but I’m guessing that by the time that the pH of the starter or levain is low enough to inhibit LAB reproduction that the amount of available food for the yeast is likely also limited and that might be the rate limiting step that prevents the yeast from continuing to expand.
Hopefully Debra Wink, Michael Wilson or Doc Dough will be able to respond to your question because it is a thought provoking one.
LAB outnumber the Yeasts.
Not greatly! The very nature of a starter is favoured for LAB. What we can do is alter the taste. The longer it's fermented for the more acid is produced. In this equation one has to take into account temperature. When first fed the pH level has risen and as it ferments it lowers. Hence young sweeter starters and mature tangy starters. So it's more of way of controlling the byproducts rather than the LAB to yeasts. Having said that we try in some way to control the LAB and yeasts for a favourable outcome by controling the conditions that favour one or the other however odds are always tipped in favour of LAB and it's more a case of controlling the level of fermentation and therefore byproducts.
We make starters by souring a "dough". Mix flour and water, wait for it to ferment and sour, and a starter is made. It is perpetuated in the same way be it in the starter, levain or final dough which can be used as a starter for the next dough. We come full circle. Although it's become more usual to keep a starter separate but same difference.
However all three have the same process and are fermented flour and water. One feeds the other and it's perpetual.
Abe, your comments are well put and well taken. Your ability to simplify the matter is insightful and helpful.
If I was only able to recommend a single baker to help someone get their first time starter up and going, without hesitation and on every occasion it would be you!
Here is an excellent article on this very subject and the following is an excerpt...
I must point out that my 'knowledge' is only what I've picked up over the years and comes mainly from making, maintaining and using a starter. I'm no expert. For that we need our resident microbiologist Debra Wink. Sometimes I'm right often I'm wrong. But at the end of the day I've learned enough to make a decent loaf of sourdough without knowing exactly what's going on under the microscope. I make mistakes along the way and learn from them. Hopefully I pass on just the correct useful stuff.
This is an important distinction. If the LAB:yeast ratio were, say, 20:1, then the total cell mass ratio would be just 1:1. I’m not sure how directly that correlates to metabolic activity (and therefore food consumption and the resulting byproducts), but this tells us that focusing on the ratio of cell numbers would be an oversimplification.
So for every 100 LAB there's 1 Yeast. So LAB outnumber yeasts 100x yet Yeast Cells are only 20x bigger. Whatever the case through numbers or mass the LAB outnumber and outweigh the yeasts.
And as we know LAB turn up quicker and are less heat sensitive than yeasts. That's why in the fridge yeasts come to a standstill and LAB carries on and in other starters like CLAS and Salt Rising Starters they're kept at a high temperature which supresses yeast growth and promotes LAB. Seems like LAB are the most adaptable of the two.
And a starter/levain is only stable when there is enough LAB and has an acidic environment. They're the first to turn up, quicker off the mark.
My guess is yeast are more alcohol tolerant. Any thoughts? Is that true? Anyone tried adding vodka to starter?
Yeast can't take too much alcohol. They are used to make alcohol by eating the sugar and making alcohol as a byproduct but they have a ceiling (an upper most limit) and begin to die off once that has been reached.
Well, what is too much? The yeast are at least adapted to some alcohol (wine yeast survive up to ~15%!), while I think LABs wouldn't normally encounter any significant ethanol concentrations... But I don't know for sure, need to check the literature.
Don't forget alcohol today is often made like yeasted breads today. It's added to the mixture and bred for different strengths. When they've reached their limit, whatever it is, they drown in their own waste product - alcohol. Alcohol is a waste.
But we've gone off on a tangent.
OK, I'm back at my laptop - and a quick google suggests LABs are relatively resistent to ethanol, similar level to yeast (inhibitory concentration between 6-15%, that is of course studied in the context of beer production), but to a varying degree depending on the specific isolate. But it is mentioned LABs are particularly resistant compared to other bacteria. Considering that, maybe a little alcohol would be beneficial to establishing a starter!
Not sure if it's accessible for free: https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-2011-0124-01
Doesn't mean the same as creating an ideal environment to get a starter going. Just means they can survive in that much alcohol as supposed to encouraging LAB to grow.
The initial bubbling up in a starter doesn't have to have Leuconostoc bacteria (often does but not necessarily) and LAB is present. What's more many starters continue to have Leuconostoc bacteria as part of their symbiotic culture. When the Dunn Lab released their study it showed many starters supporting Leuconostoc bacteria as well as LAB. And I don't think Leuconostoc bacteria prevent a starter from being born and it's just part of the natural process. A lot of times it's a difference between a six and 2 threes. People can take a week or more with the pineapple way and I've made a starter in 3 days just using flour and water. Another excerpt from the same article.
Ilya was spot on to say that most wine yeast handle up to around 15% abv and yes high levels of alcohol produced by yeast do eventually become toxic to themselves.
Many winemakers use spontaneous fermentation to make their wine and this selects the yeasts most able to complete the wine to dryness (no free hexose sugars). Over time the most suitable yeasts are selected again and again and become dominate. Some wild (non inoculated, but trained) yeasts can handle up to 17.5-18% abv. Organic Amarone or Californian Zin being examples. Very tasty they were too!
Alcohol should indeed be better tolerated by yeast compared to LAB, that is a definite! But in sourdough the alcohol level is never high enough to be a significantly influential factor.
Wine regularly comes in at 13-15% ABV average. Some more some less. However not really anything to do with our starters. Not really wanted in our starters either!
How did we get onto wine again? I do like a good wine though.
Alcohol is key to flavour. Without alcohol bread would be less flavoursome.
Alcohol (eth-anol) and higher alcohols (prop, but, pent, hex etc.) produced by yeast can then bind with carboxylic acids to create aromatic esters. It is this very reason that wine can smell like all sorts of other fruits.
Although unfortunately when we bake bread we cook off many aromats but some other complexes remain.
Esters and many other types of aromatic compounds make the flavour, because flavour is mostly in the nose!
This is what I've been saying through all my posts. By products and taste. But I think wine and starters, in or out, is straying from the point. And the level of alcohol in wine is much higher than in our starters.
You suppress the LAB and have a yeasty starter. Well firstly it's not a sourdough starter anymore and secondly why not just make yeasted breads? Then you'll have 100% yeast.
You guys get much deeper into this than I do! Flavor-wise, this has served me well:
Bacterial Fermentation
Bacteria are primitive one-celled organisms. The types of bacteria common in bread dough consume the same simple sugars used by yeast cells. The primary by-products of bacteria in dough fermentation, though, are two types of organic acids: lactic acid and acetic acid. Lactic acid is also found naturally in milk and in concentrated form it produces the tangy flavor we find in yogurt. Acetic acid is found in all varieties of vinegar and is more sour than lactic acid.
ORGANIC ACIDS PROVIDE STRENGTH AND FLAVOR
The types of bacteria that produce these acids can thrive in temperatures of 50-90F and are collectively referred to as lactic bacteria. As bakers, we are concerned with two types of LAB, homofermentative and heterofermentative.
These names may seem hard to pronounce and even harder to remember, but it is important to identify them and explain a bit about their behavior. Yeast must be regulated to control how fast the dough rises, but the bacteria primarily determine how well your dough will mature and how the bread will taste. If you want your bread to develop good handling properties naturally and to taste good, you must pay as much attention to the quantity and type of bacteria in your dough as you do the activity of the yeast.
This is, perhaps, the one concept in artisan style baking that escapes bakers who look for easy, time saving ways to make bread. Unfortunately, bacterial fermentation almost always proceeds more slowly than yeast fermentation, much more slowly. Scientist have successfully isolated strains of the yeast saccharomyces cerevisiae that can speed carbon dioxide production considerably. Lactic bacteria have so far been much less cooperative; the bacteria in bread dough we make today probably aren’t different from those present in the times of Moses.
HOMOFERMENTATIVE BACTERIA
Homofermentative bacteria prefer environments that are wet and moderately warm, perhaps 70-95F. Their chief by-product during fermentation is lactic acid which is fairly mild in it's sourness compared to the sharper acids contained in lemon juice or vinegar. Homofermentative bacteria can survive in somewhat drier conditions and within other temperature ranges but they do better in the warmer range.
HETEROFERMENTATIVE BACTERIA
Heterofermentative Bacteria do better in somewhat drier and cooler environments, they prefer temperatures of about 50-65F. They produce both lactic acid and acetic acid as by-products as well as a small amount of CO2. Acetic acid is also found commonly in vinegar and it’s flavor is much sharper that that of lactic acid. Heterofermmentative bacteria can survive in some numbers as different temperatures than specified and in wetter environments, but drier and cooler situations favor their reproduction and their ability to ferment bread dough.
Daniel T. DiMuzio, Bread Baking.
The replies have been interesting, but it seems the discussion is not addressing the original question.
I reiterate. Is it possible to change the ratio of yeast microbes to LAB microbes in a significant way. Let’s say the ratio is 1 yeast cell for every 100 LAB cells. Is it possible to convert a starter that will have 5 yeast cells for every 100 LAB cells?
I am convinced that we can alter the byproducts of the yeast and LAB. Because I hold that statement true, I believe that the flavor and also the dough conditioning aspects of a starter can be directed in one direction or the other is short order. For example, a very “sweet starter” (not fed sugar, but not acidic in relation to taste, flavor, and TTA) can be quickly nurtured to produce loads of acidic byproducts. To prove this point, take some of a “sweet starter” and put it in a very warm place (86-93F). Leave it alone for 12 - 24 hr and then make a determination as to if you believe the first two statement of this paragraph.
BTW - we can also go in the opposite direction, sour (acidic) starter to sweet.
Back to the original question in the OP.
” Is it possible to change the ratio of yeast microbes toLAB microbes in a significant way. Let’s say the ratio is 1 yeast cell for every 100 LAB cells. Is it possible to convert a starter that will have 5 yeast cells for every 100 LAB cells?”
I appreciate the replies rec’d thus far. Statements that we agree on are confirming, but the most important statements are generally those that we don’t. Those make us think...
The basis for the specific question is revealed in the third paragraph.
IF it is possible the affect the ratio of yeast cells to LAB cells to a great extent, then the idea that a non-acidic starter can be manipulated to produce much more acid (higher TTA) is conditional.
Consider two starters
Starter #1 has 1 yeast cell for every 100 LAB cells
Starter #2 has 5 yeast cells for every 100 LAB cells
Given identical fermentation environments, wouldn’t Starter #2 be many times more difficult to produce the same amount of TTA compared to Starter #1?
The reply went long, so this thought was posted below in a separate repky.
We are all aware of Dab’s No Mess No Fuss starter concept. I love his innovation!
But if you think about it, the starter is left to ferment for a super long time in the refrigerator. It is commonly accepted that cool temps setup an environment that favors LAB more than yeast. So, what is actually happening during the extended stay in the refrigerator?
Is the starter
We can all probably make a guess, but what is really going on in this senario?
Because IF the cell ratios of yeast and LAB are not changing, then the starter has a higher amount of LAB byproducts. We have more acid, not a larger ratio of LAB cells. With that in mind, consider the levain made with this starter containing more acids, not more LAB cells. We inoculate the levain with 5% starter. It is true that this starter brings more acid to the levain, but at 5% inoculation, that is relatively little.
Dan I think that link is back to this very thread. DAB’s NMNF starter thread is http://www.thefreshloaf.com/node/40918/no-muss-no-fuss-starter I believe.
Because in a stable starter or levain the ratio is 100:1. Lactic acid is simply a by-product produced. Stop the production of yeasts and this gives time for LAB to carry on. Feed said starter and it sorts itself back into 100:1. It's symbiotic which need stability and that is the stability.
And even if one could you still taste either the unfermented sugars or the by-products.
Is because it hasn't fermented enough to produce enough lactic acid. In other words there's still a lot of available sugar. A mature stable starter and levain has lab outnumbering yeasts by 100:1.
Think of it like this. What you are tasting in a sweet levain is more available sugar that hasn't been converted. The tang you taste in a more mature levain is the by product lactic acid and there's less available sugar because it's been consumed.
Yes and the acids that have been produced haven’t overcome the buffering effects of the flour yet. They are in the levain/dough/starter but not to the extent that the flour is no longer able to buffer them thus you cannot taste them yet.
We need a stable starter. In a stable starter the ratio is 100:1.
When we make a levain and by extension the final dough it begins to eat and turn it into 'starter'. What we taste is a balance of one or the other. Not yet fermented sugar or lactic acid.
Let's say we could change the ratio (for argument's sake) the above still stands.
Benny, it is my assumption that, even though the culture is buffered, the acid flavor and also the dough conditioning derived from those acids are not affected. Only the PH. Is this correct?
That I am not sure of Dan, I’m not sure when the lactic and acetic acids are buffered whether or not their flavour is affected.
I found this article https://www.preparedfoods.com/articles/106574-article-matter-of-balancing-taste-october-2008 now this isn’t specifically talking about bread but I think some of it is pertinent,
A quote from the article.
“Although scientists initially theorized that sour taste was solely a function of the number of hydrogen ions in a food or beverage, this simplified view of sourness is no longer considered accurate. Instead, scientists now believe sour taste is a function of pH (-log [H+]), as well as several factors associated with the acids used in a formula, such as concentration and quantity of undissociated acid. To illustrate this point, sensory scientists performed studies on the perceived sourness of acetic acid and citric acid, as compared to hydrochloric acid. Although all of these solutions were maintained at the same pH, sourness ratings for acetic acid and citric acid were higher than those for hydrochloric acid.
Although scientists do not know pH’s exact role in the perception of sourness, changes in the concentration of free hydrogen ions in solution influence sour taste and intensity. To compare the relative sourness of different acids in a food or beverage, all products must be evaluated at the same pH. Without this control, one acid perceived as less sour at a higher pH may actually be more sour at a lower target pH.”
I think this means that at a lower pH, high concentration of free hydrogen ions in solution, there will be a greater perceived sour taste than at a higher pH, lower concentration of free hydrogen ions in solution.
Someone correct me if I’m wrong, I studied chemistry and biochemistry more than 30 years ago.
I know something about that, having studied, participated, and delivered sensory evaluations.
I have tasted diluted samples of acetic, citric, lactic, succinic and tartaric acids as part of a sensory evaluation class.
When it comes to taste, yes different acids have a differently perceived character at the same molar concentration. Acetic is generally the most offensive. I previously mentioned about it here.
We don't taste pH as such we taste more the total acid. Our saliva is packed full of electrolytes (ions, positive and negative) so that when we eat our saliva can buffer acidic and alkaline substances to help maintain an equilibrium. Also our saliva contains antimicrobial compounds like lysozyme to help prevent infections.
Note that citric acid is triprotic whereas acetic and lactic are monoprotic. This means that citric can donate three H⁺ ions while acetic and lactic can only donate one H⁺ ion each.
In effect the higher the TTA the more acid will be perceived, but the quality depends on the acids present and other components. And at the same pH the TTA could be high or low. It depends on the constituents of the solution.
It would be fair to say that solutes like sugar and salt can affect the LAB:yeast ratio but most typical starters don't feature either. Continuous old dough processes being a notable exception.
I have long avoided such conversations because they are fruitless. Face fact, you can't measure this, you can only speculate.
Lucky as I am I have sampled, serial diluted and plated microorganism to then count them (enumerate) to arrive at a CFU/g measurement.
Yes most starters stabiles at around the 100:1 (LAB:yeast) mark. But this is really to do with the cell size difference as I said here and below.
Michael, you are the friend mentioned in the OP. It was this exact post that started my thinking on this subject.
So, when we manipulate our starters (more acid, less acid, etc) we are affecting the production of byproducts and not the actual microbe populations. Is this correct?
I’m glad to joined in on this conversation.
Isn't LM an example of where process conditions have been modified to reduce the amount of acidity in the starter?
Lance
But the question is whether the ratio of the population of yeast/LAB microbes are altered OR the the production of byproducts are affected by their specific environment.
I really enjoy post that probe deeply into matters. Don’t understand all of it, but that doesn’t deter my inquisitive nature :-)
So the original question you asked was
"Is it possible to maintain a starter in such a way as to greatly alter the ratio of yeast (fungi) to LAB (bacteria)?"
Doesn't an LM starter do just that?
Lance
No. A mature LM has a LAB:yeast ratio in the 100:1 range as per any typical starter.
In that case, why do we bother making one?
Where there is reduced acid load there is increased fermentation.
Lance, I hope I’m not missing the point.
I think a Lievito Madre and a typical sourdough starter are identical as far as microbial population is concerned. The rigid maintenance of the LM is meant to direct the byproducts of the microbes and not the actual population of those same microbes.
Is this correct Michael?
I think for the above reason, Michael tells me that a typical sd starter is just as good as any other type sd starter to start a Lievito Madre. The ratio and populations of the two groups (yeast and LAB) are identical in any healthy sd starter (100:1).
So, how is it the ratio of yeast to LAB remain a constant in healthy SD starters. Mike explains this is a matter of individual cell size. LAB cells are much than yeast cells. He told me the size difference but I don’t recall what it was.
You need change your cognitive approach here and stop thinking in such absolutes. Don't get hung up on the 100:1 thing. The reason it is written is the result of numerous studies and the figure itself is an average probably to the nearest 10. Each and every starter at any given stage through its cycle will vary with respect to the LAB:yeast ratio. Could be 200:1 or 33:1, it's never exact. These are living things, variability is huge!
Regarding LM yes the approach is mostly about optimising the by-products but at the same time because it is frequently refreshed we are maximising the microbes, both yeast and LAB to ensure a very potent fermentation power.
I've seen LM creation procedures that start with a yeast water, eg apple. Presumably these will have much less than 100:1 ratio, at least for a while?
Lance
Michael, my concern isn’t about the exact or even approximate number or ratio of Yeast to LAB, but I am trying to understand if the ratio of the populations of yeast microbes and LAB microbes in a given starter can be drastically altered.
Until recently I was under the impression that we could maintain our starters in order to greatly increase the relative population of one (yeast or LAB) over the other. So for example let’s say a starter has 1 yeast cell for every 80 LAB cells. I wondered if we could alter the starter to have 1 yeast cell for every 40 LAB cells. (The numbers are arbitrary and only used to serve as an example).
I am trying to learn if, when altering a starter (for rise, sourness, sweetness, etc) we are changing the actually ratio of Yeast microbes and/or LAB microbes. Or are we working to alter the metabolisms of one group (yeast/LAB) over the other in an effort to increase or decrease their byproducts.
The nature of sourdough starters being a symbiotic culture of yeasts and bacteria keeps a starter at roughly 100:1 bacteria to yeasts. In other words even if we can't be exact on the actual ratio for a starter to keep its symbiosis the bacteria will always outnumber the yeasts by a lot. The bacteria and yeasts depend on each other and exist happily when kept in this balance. When we make a starter it matures when the balance is found. A healthy starter propagates itself by keeping this balance.
Sweetness doesn't depend on more yeasts. Sweetness comes from sugar that hasn't been converted. So not because there's all of a sudden too many yeasts. Tang or other variations comes from the by products of the fermentation and generally once the food begins to decline. Once this happens it tips in favour of bacteria or more accurately it tips in favour of the byp-products vs. undigested sugar. So we always have a symbiotic culture of bacteria and yeasts from the start. Allow it to over ferment and bacteria gets the upper hand. Feed it and give it TLC and the population of yeasts recover but not beyond the symbiotic balance.
You're thinking because it's sweeter there's more yeasts. It's sweeter because there's more sugar that hasn't been consumed. Tang comes from food running low and a shift in the metabolic rate, sugar is greatly reduced, acidity builds up, alcohol is produced and if left too long they die in their own by-products. Feed it and they perk up to start the process again.
Not scientifically put but something along those lines.
Another thought... When we say a yeasty starter do we mean yeasty or not as tangy?
Take a yeasted bread. Why not add a ton of yeast and get a bread in 30 minutes? Reason is there's other things going on inside the dough other than yeast giving off gas. The long and short if it is the flour when mixed with water begins to break down turning it into simple sugars and so on. Just puffing up a dough quickly doesn't make the tastiest bread. On a similar vain we can apply this to sourdough except a sourdough starter gives it another dimension with the inclusion of lactic acid bacteria.
Thanks Abe, I have no idea how my question can be more clearly written. If anyone can define my question more clearly, please help me out.
I realize that the characteristics of a starter, such as sour and non-sour (sweet) has everything to do with the byproducts or lack of byproducts and not with the microbes themselves. I realize that carbon dioxide and other gas (byproducts) are what raises a dough and not the yeast themselves. Also, I get that the acids and other byproducts produced by the LAB are what gives flavor and condition the dough and not the LAB microbes. For example - I believe a super active starter that has an extremely high cell count of both yeast and LAB can be maintained in a way that causes the starter to produce a bread that has very little or no sour flavor. And that this is accomplished by limiting the metabolism to of the LAB to produce less byproducts.
What I am curious to know is whether a baker can control the feed and/or environment of a starter in order to change the basic ratio (I am not concerned with exact numbers or ratios) of yeast cells in relationship to LAB cells. The question seems very simple, but the answer may be the same.
I am inquisitive and interested to learn...
There are many things that I’ll never know and this may be one of them LOL
I appreciate the the efforts of everyone that replied.
http://www.thefreshloaf.com/node/66356/acid-washing-yeast-lievito-madre
Acid washing. Or more correctly washing the acid away will make it stronger and more active because acid is a by-product and waste. Same goes for CO2 and same for alcohol.
Acid washing is a bit different Abe. It uses a dose of acid to kill off bacteria - routine in brewing, but highly experimental in baking - as in, there's only me that's done it!
Lance
I thought you meant giving your LM a bath to wash acid away (which is done) not the other way around.
If it's a waste then what effect does it have on the yeasts? Too much acidity, below the norm of a starter, I think will be detrimental to yeasts as well. I'm thinking washing the bacteria in a starter away which will be below the pH level of a normal starter will also be detrimental to the yeasts. No?
In brewing once it's washed to get rid of the bacteria it then goes through more processes and yeast added in.
Conditions have to be carefully controlled pH 2.1, temperature 3-4C, defined duration. Yes, the yeast takes a bit of a hit, but recovers.
"In brewing once it's washed to get rid of the bacteria it then goes through more processes and yeast added in."
No - after acid washing the yeast is pitched directly into the normal wort in the fermenting vessel.
Lance
Isn't wort the water in which the grain has been boiled in?
Mashing: ground malted barley + hot water to give a mash temp of 65C converts malt starches to sugars. Duration 1.0-2hrs.
The mash is then sieved and rinsed (sparging). The filtrate is known as sweet wort. The residue is spent grains.
Boiling: the sweet wort is boiled in the copper with hops. Duration: 1-1.5hrs.
This liquid is now known as wort and is cooled and run into the fermenting vessel where yeast is added and a few days later you have (yeasty) beer!
Lance
A 'super active' starter will still be symbiotic and keep the yeasts and bacteria at a stable ratio!
A starter which isn't super active has either been over or under fed in which case both the yeasts and bacteria have been whittled down or waste matter has built up so much they're struggling.
I also think if a starter ever gets unbalanced it'll always favour the bacteria hence the poor rise. So happy and healthy starter is one which is balanced and symbiotic. An unbalanced starter will be too much in favour of bacteria. A 'yeasty' starter is one which is not acidic and the yeast is at an 'optimal level' which is about 100:1.
Imagine a wall, you on one side, the microbes on the other. You can observe their outputs as their by-products pass through the wall. You can make qualitative and quantitative assessments of the outputs but you can't observe what is happening behind the wall, you don't have access.
You might think your question is simple but what exactly does "drastically" mean, quantitatively?
You can make changes on your side that affects the level and composition of the outputs, but you can never know how many individual LAB or yeast cells there are, you can only guess regardless of any step you take.
Using information from studies that have observed and quantified both sides of the wall we can infer and make assumptions. Still we (bakers) don't have access.
Based on my understanding I can say for any sourdough starter that contains only flour and water, when established the LAB will always outnumber the yeasts.
Abe's point about symbiosis is a good one. And as I have said LAB cell numbers are higher than yeasts because their cell size is that much smaller. They require less energy per cell.
Owing to the nature of flour with the addition of water it's a great place for LAB to grow. (ideal pH) And to keep them in there it is necessary to feed more flour to raise the pH back up again by diluting acids.
For all starters including LM we still apply some of the same process parameters. I.e. We feed flour and water when (or before) it stops rising and we keep it at temperatures that are not so high as to be a detriment to leavening.
Thanks for the visual, Michael. I helps me understand that we can observe the byproducts. Not so much the numeric populations.
But the interesting takeaway was the statement about feeding the starter with flour and water raised the PH (by diluting the acids) so that the LAB could continue to reproduce. The word “reproduce” was carefully chosen. It is my understanding that once the PH drops below a certain level, the LAB are unable to reproduce but they still produce acids as a byproduct of their metabolism. Is this correct?
One more question -
It piggybacks off the first one. Once a starter peaks, if it is stirred down, we know it will rise agin quickly and even rise higher. But your statement about raising the PH (by feeding) to allow the LAB to flourish (reproduce) again has me wondering. I assume that stirring the starter brings fresh food in contact with the microbes, both yeast and LAB. But when we do this, how is the starter in general and also the LAB affected? The PH is still low. What do you believe is taking place in the starter if it is stirred down one or more times upon maturity (peak)?
I promise, the last question -
Is stirring down a starter or levain a viable method to increase TTA?
Thanks for putting up with me :-)
Too much emphasis on the visual and not what is going on.
When a starter has peaked it is saturated with yeast and bacteria. But this doesn't mean the food is completely depleted and stirring it back down doesn't mean its not fermented nor does it mean it hasn't peaked.
Once its peaked we have a lot of yeast and bacteria fighting for less food unlike when first fed where a small amount if starter has a lot of food.
I think stirring down is like squeezing a sponge. Wringing out every last drop.
What happens if you don't stir it down and it just collapses but continues to bubble away? I find this happens in Hamelman's levains. Doesn't collapse all the way but finds a new equilibrium and happy continues to ferment.
In baking there's lots of advice and tradition which isn't always necessary. Stir it don't stir it's the same. A young ferment is sweeter and the further you take the ferment the more the acids build up. Happens if you stir it or don't stir it. Somewhere I read the Yeasts and bacteria don't have to he taken to food as they're more than capable of permeating a starter. As with most things we do things a certain way just because of tradition.
I always thought ‘peaked’ meant when the CO2 production had ceased, also known as exhausted. This can and does in may cases occur long after the maximal height has been reached.
The other is the effect. Generally in sourdough most people understand it as fed, risen, peaked and falling. Most people don't factor in stirring down and allowing it to rise again when they speak of peaking. Never has recipe I've seen spoken of a starter peaking in any other sense. Perhaps there is residual food left but the starter is saturated with yeast and bacteria competing with little food and will still start the process of becoming acidic.
Again... Terminology! We can all discuss the microbiology of what's going on under the microscope forever. We've long gone past then original question which has been answered long ago. Over and over again.
The problem is you don't know the the starter is saturated with LAB and yeasts, you assume. Only lab-work can provide that insight.
Are you not familiar with the idea that a starter can "hold its peak"? What I'm saying is that reaching the maximum growth volume is not proof of CO2 production stopping and therefore not proof of cellular numbers.
Words are not like like numbers, there is much fluidity in how we use them to convey what we mean.
Like "over-proofed / over-proved". That could mean about six different things.
Proteolysis can cause structural collapse, yet there could still be plenty of food around.
It's visual. When it has peaked for and it begins to fall the more the acidity builds up. i.e. the further along the fermentation process the higher the acidity. My ideas on yeast to lab ratio is constant.
Perhaps peaking to a microbiologist will differ to someone who's baking. We often go by visual aids and therefore it'll be different.
Excuse my abrupt last post Michael. I think my interest has been peaked and has started to fall ?
I do think the original question has been answered and now we've strayed into terminology and deeper down the rabbit hole of sourdough starters. Should have taken the blue pill.
Michael, is there a practical method that a home baker could implement to gauge gas production in a starter? I have long used the non-scientific latex glove, but it lacks any degree of precision.
wouldn’t we able to gauge the raising power of a starter if we could measure the gas it produced?
Danny, what about Doc's weight loss method to gauge lost CO2? I don't know the details but I'm sure he can fill you in.
Lance
Doc method says that when at least 2% of the total weight of the flour added
(including the flour in the seed culture)has decreased form the total weight of the starter it is mature. He advocates belching the starter when measuring the final weight of a matured starter to remove excess gas.It would be interesting to measure the PH and also the weight lose to compare findings.
And how does he differentiate between CO2 loss and evaporative moisture loss? I guess an airlock (as used in home winemaking) would do the trick.
Lance
Maybe Doc will write in. He cover the starter to prevent moisture lose. The starter is tapped on the table (belching), then gas release (I think) before weighing.
Do you have a link to the original discussion? I've been feeding very dense whole grain starters where the standard feedback mechanisms aren't relevant and am very interested in this.
http://www.thefreshloaf.com/node/59410/starter-use-and-maintenance
http://www.thefreshloaf.com/node/51875/judging-levain-maturity-weight-loss
http://www.thefreshloaf.com/node/57518/individual-starters-and-their-unique-characteristics#comment-418465
Thanks. A curated list of TFL posts would be the basis for a good baking ebook.
Yes, correct. Growth of LAB are limited by pH. Acid production continues all the while there are viable cells and an available food source.
The microflora of LAB and yeasts only exists because we feed them. Not just because it brings food (sugar) but because it creates an optimal environment for their growth. If you were to feed with just sugar (no effect on pH) in the form of maltose, which is the primary source in SD the LAB would eventually die off because the pH would continue to decrease to the point where they are unable to grow. Yeasts are not directly limited by pH however.
The maximum height of rise is limited by the physical properties as too is the rate of collapse which is based upon leakage. It is quite incorrect to think that once any given starter has reached it maximum rise height the growth of the microbes has ceased also. This is where measuring pH can be useful since LAB growth tends to slow at around pH 4.0, ceasing at around 3.7-3.8. These pH points mark an ideal time to feed again.
This is where measuring pH can be useful since LAB growth tends to slow at around pH 4.0, ceasing at around 3.7-3.8. These pH points mark an ideal time to feed again.
This I have not seen before Michael and is very interesting and helpful. I definitely learn more than one thing each day thanks for contributing to that.
Benny
Michael, you know I just got a very nice PH meter. To make sure I don’t misunderstand the proper method of using a PH meter, would you elaborate more? Should the starter’s Ph be monitored until it drops to 3.8 and then re-fed?
It should be a learning experience to monitor the PH while comparing it to the starter and it’s rise.
I am also tasting and smelling the starter at know PH levels in order to develop a sense for determining PH. It seems the taste changes quite a bit with various PH.
I think you can change the way the yeast feed, changing their food, in such a way to break their simbiosis to bacteria long enough to cause major changes in bacterial metabolism or at least the bacteria groups supporting the yeast.
A lot of studies have been done with yeast and their metabolism. DNA switches activated by extreme environmental changes is something to look into. Swiches can be activated and passed on for generations of yeast organisms. I found this especially interesting when developing a starter with high amounts of table sugar (example the amish friendship starter) resulting in sourdough starters that are sweet even when over fermented. Why not try making such a starter from scratch and see where it goes?
I also want to add that I don't think yeast kill themselves in their own waste, yes, their numbers most likely are reduced but at some point of saturation, they spore or preserve themselve for more inviting enviromental changes, and their byproducts will help protect them until conditions change. Anyone test that hooch in the back of the fridge for alcohol content? And those bugs on the bottom can often be revived after a few days of TLC.
And a starter is symbiotic wouldn't that be damaging the starter? Or making it unhealthy? If the wild yeasts in a starter thrive in these conditions wouldn't it be counterproductive?
And if someone wants only yeasts why not bake with yeast or yeast water?
Acid washing wouldn't kill all the bacteria - only some of them. Kill rate would be defined by duration.
And the bacteria do 'mop them up'. So while it can be revived their numbers have dwindled. But the cold storage can preserve them.
I'm also of the opinion that spend any longer then a few days 'reviving' a starter, it's a new starter.
A strong starter, and a happy starter, is one which is in perfect symbiosis. Strong not meaning more yeasts or filling the balance in favour of yeasts. Strong is when a starter is fully functioning as it's supposed to do. Flavour is a balance of fermentation.