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Very liquid sourdough

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nicodvb's picture
nicodvb

Very liquid sourdough

Hi,
I read that most of you use a sourdough with 100% hydratation, just like me.
Recently I came across a more liquid sourdough (130% hydratation) that doesn't actually rise (a lot). It has the consistence of yogurth but it thickens during refreshments. It's supposed to develop exclusively lactic acid (none of acetic acid), and to grow the yeasts better

Did anyone ever use it? Can you share your experiences? Can you explain the differences?

Thanks,
Nico

dghdctr's picture
dghdctr

Hi Nico,


Here in the U.S., many bakers have read a book by Nancy Silverton, who founded the LaBrea bakery in Los Angeles more than a decade ago.  I believe her liquid levain was hydrated at around 140-145%.


That extra wetness makes the stuff easy to stir, which is an advantage if you're making hundreds of pounds of it.  It also tends to push the bacterial activity more toward the production of lactic acid -- which is milder -- and somewhat less toward the production of acetic acid -- which is more sharp in flavor.  And the actual process of fermentation (for both the wild yeast and the bacteria) will proceed more rapidly, generally, than it would for a firm levain.


Still, I doubt that literally all production of acetic acid would cease.  Factors like ambient temperature, the size of feedings, and the length of feeding intervals also affect the acidic qualities of a sourdough starter.


Wild yeasts found in a stable sour starter are more resistant to acidity than manufactured yeast, but even they have limits to their tolerance, so I guess it could be said that a higher hydration starter should present fewer challenges with high acid content.  But those same wild yeasts work pretty well under drier, slightly more acidic conditions as well.  I think it is the extra water in a liquid levain that may be more responsible for any accelerated yeast fermentation activity, but we'd need an expert like Debra Wink to give us any real scientific insights there.


--Dan DiMuzio

Debra Wink's picture
Debra Wink

Whenever I contemplate answering on a topic as expansive as this one really is, it wears me out just thinking about it, because I think a whole chapter could be written on starter maintenance and how it affects population dynamics and metabolite production. Click here for an introduction to the latter.


I wouldn't change anything that Dan said, but I will add that you will never get all lactic acid, or all acetic acid, no matter what hydration you keep your starter. All else being equal, you will get a lower percentage of the total acid as acetic, at the higher hydrations. Acetic acid will increase as a percentage of the total acid, as the hydration moves downward, but it will never be higher than lactic acid. Lactic acid will always be higher than acetic in a starter or bread dough, no matter what hydration you use.


I recently tried Hamelman's Vermont Sourdough (built on a 125% starter), because it received so many accolades here on TFL. In fact, I tried it twice, because I wasn't sure the first batch was what it should be. I may be the only one, but I didn't care for this bread at all. It was just too sour for me (and I didn't even retard it). But as you can probably guess, I am not a sour seeker. Next I tried the Pain au Levain. It is essentially the same overall formula---same dough hydration, and same percentage of pre-fermented flour. The difference is that it is built on a firm 60% starter, and has 5% rye flour instead of 10. Seemingly small changes, but what a big difference it made in the character of the bread. This one, I loved. It was mild in flavor, and had the most heavenly wheaty aroma.


So, why does my firm starter produce milder bread than my liquid one, when firm starters have a higher percentage of acetic acid? Because it has a lower total acid concentration. More specifically, the bacteria grow slower in a dry starter, so their population shrinks over multiple refreshments (yeast seem to hold their own). Because their population is smaller and they're growing slower, acid production is likewise reduced. But this brings us around to the other factors, which Dan has listed above---temperature, the size of feedings, and the length of feeding intervals. These also play a big part in population dynamics and acidity.


Today, I shall leave it at that  : )
-dw

dghdctr's picture
dghdctr

I've never read a more complete (and yet concise) explanation of the complex factors that affect sourdough flavor profiles.  Thank you!


--Dan DiMuzio

nicodvb's picture
nicodvb

I'm really happy to have raised the question because a lot of extremely intersing informations are coming out.


Thanks a lot to both, it's an intriguing matter!

nicodvb's picture
nicodvb

I have another question for you experts:
generally speaking, is the yeast concentration higher in a liquid levain or in a firm one?
In Italy there's almost no colture of liquid sourdough (only firm) and all recipes involving a lot of fats and requiring a very high rise mandate the use of a firm sourdough (it's called mother dough, here).
Professional bakers often repeat that liquid sourdough doesn't have the "strength" to rise panettone and pandoro, that you need a real mother dough refreshed every day at least for a weak to strengthen it enough, but I won't believe them until I find some scientific evidence.

For sure my panettone and pandoro take a lot of time to rise when made with my liquid sourdough, but maybe it's just me.

dghdctr's picture
dghdctr

Hi Nico,


If you want meaningful comparisons of population counts, we'd need Debra to provide an answer.  Still, I think I can address your question w/regard to yeast activity in general and about the comparative "strength" issues you describe.


First of all, I'd have to say that without actually observing both the levain and the final dough that you or they might be using, I can only speak in generalities.


Generality #1 might be that the metabolism of sugars in a levain (otherwise known as dough fermentation) will occur more rapidly in a liquid environment than it would in a firm environment.  "Liquid" and "firm" are imprecise terms in a way, but we both know what I mean here, right?  Take the same qty of flour in two separate doughs and hydrate one at 100% and the other at anything less than that (let's choose 60%), and the one hydrated at 100% will undergo a more rapid rate of fermentation.


So it's reasonable to expect that, as long as both the liquid and the firm levain we're comparing are at their peak of development and kept at the same temperature -- ripe and ready to be fed or used in dough -- it is the liquid version that may be exhibiting a faster rate of gas production.


The potential "strength" of the two types of levain is a somewhat different consideration that mostly results from their acidity and their enzyme activity.  Up to a moderate point (and there is a limit to this effect), a somewhat more acidic levain can provide more physical strength to a final dough than a less acidic levain.  This is not to suggest that more acidity (lower pH) always makes bread dough stronger.  But at moderate acid levels, it might be said that a levain at pH 3.5 could strengthen a given dough more than one at pH 4.0.


Again, I have to generalize here because there are other factors than just hydration that affect the acidity of a levain, but a more liquid levain tends to de-emphasize the acidity, while a firmer levain tends to increase the acidity.  So if you're looking to maximize strength in a final dough, then firm levain will do that a bit more than liquid levain -- usually.


Also, liquid levain will feature a faster rate of enzyme activity (for both amylase and protease), and this faster activity can de-stabilize a dough if that dough is fermented for prolonged periods of time before baking.  If your dough is fragile to begin with, or you need to hold finished shapes overnight, liquid levain might work, but firm levain is at least less likely to cause issues with enzyme activity.


It is very normal for pannetone or pan d'oro dough to take a long time to rise, because you're using wild yeasts to begin with -- which are slower -- and because you're not able to just ratchet-up the population counts by adding more yeast.  Adding more levain to a dough is more tricky than just using more manufactured yeast, and the changes that could occur to both the flavor and structure of the dough would make most Italian bakers avoid that option.


Of course, my understanding is that the "madre" for pannetone is firm, but fed every 4 hours and kept at about 85 degrees F to minmize issues with too much acidity.  The madre they use is not sour at all, right?


So I think their warnings about using a liquid levain might only pertain to the very rich, long-fermented dough we see with pannetone or pan d'oro.  For a bulk dough or for raw shaped loaves that are fermented for only a few hours, there is no real issue with the strength provided by a liquid levain, as long as you don't use too much.


I use liquid levain all the time for baguettes (at only about 10% pre-fermented flour) more as a flavoring and maturing agent than a primary leavener, but I also use it sometimes as the sole leavener for pain au levain (at maybe 18-20% pre-ferm flour) if I want to de-emphasize the acidity a bit.  Higher levels of liquid levain impose so much more enzyme activity that I find the final dough gets to be too sticky for convenient handling (an amylase effect), and sometimes too weak from gluten being affected by the protease.


I hope that helps to answer your question.


--Dan DiMuzio

Debra Wink's picture
Debra Wink

Nico, you bring up some really good questions, because this is a very complex, confusing and somewhat contradictory area for most people to really grasp. And this has been a difficult post for me to write, because I've attempted to explain this general topic before and only a few people really "got" it. So I hope you'll forgive me for taking some time to get back to you; I've been stewing on it a bit, so as to regroup and take a new stab at it from a different angle.



Professional bakers often repeat that liquid sourdough doesn't have the "strength" to rise panettone and pandoro, that you need a real mother dough refreshed every day at least for a weak to strengthen it enough



By "strength," in this context, I think what we're really talking about is the collective power of the yeast to huff, and to puff, and to blow the bread up :-)  In other words, a strong rise, or rising power. It is the yeast fraction in the culture that provides the lift. Lactic acid bacteria (LAB) could raise dough in theory, but in practice, they fall flat. So, a good rise is all about healthy, vigorous yeast. Bacteria contribute acids which flavor dough, but also play a big part in gluten structure and rheology. In the short term acid tightens gluten, contributing to dough strength, but in the long term, it accelerates proteolysis, contributing to its breakdown. And it adds sourness that is not welcome in all breads. You'll find yeast/lift at one end of the starter spectrum and bacteria/sourness at the other. You can't maximize both at the same time; one comes at the expense of the other. Where you want your starter to be on the spectrum, depends on the bread you are making. For panettone and pandoro, it sounds like maximizing lift, and minimizing sour is the goal.


I think the key to understanding starters, is to recognize that population dynamics and metabolic effects are two separate, albeit related issues. Population dynamics have to do with organism numbers, and how they interact and fluctuate in relation to each other and to their starter environment. Whereas metabolism is about what those organisms are doing, and what effect that has on the dough. The magnitude of those effects are related to the population numbers. But the numbers are regulated largely by how hospitable the sourdough environment is to the various species, and how much antagonism there is between them. Does that make sense so far?


Dan gave us a good overview of how dough is affected by hydration (some cereal chemistry as well as metabolic effects), but now let's take a look at how the culture is affected---the population dynamics---because that will determine the magnitude of the metabolic effects. Lowering hydration will slow all the microorganisms, yes, but yeasts are not quite as sensitive to it as the lactobacilli. In other words, the growth rate of the bacteria declines more sharply than that of the yeasts. Sourdough LAB thrive in warmth at high hydrations; low hydration and cool temperatures really slow them down. Yeast benefit from this, because they have less competition from the bacteria, so they have more space, and the resources to expand. They aren't quite as hindered by low hydration, low temperature, low pH, salinity, etc., as lactobacilli are, so even if they do slow some, they gain an edge because the bacteria are slowed more. And the one thing that yeast are more sensitive to than lactobacilli---acetic acid---is reduced as the bacterial population shrinks. So, when you knock back the bacteria, yeast tend to flourish, and rising power increases as sourness decreases.


But the key to it all, is multiple refreshments. It's the regular dilution through feeding that shrinks the bacterial population here, because they aren't keeping pace with the yeast, relatively speaking (and starter ripeness, and readiness for feeding is determined by yeast rise and fall). Because it takes some time for the populations to change and re-stabilize, a starter maintained firm (and fed frequently) for at least a week is probably going to give you better results in your panettone than a liquid starter, even one that is firmed up "as needed." It's the difference between a true firm starter, and a firm pre-ferment. The effect will be different, because the populations are different. In a firm culture, you are actually manipulating the starter environment to suppress bacteria (sour) and enhance yeast (lift), whereas a firm pre-ferment is more about manipulating the metabolic effects to increase acetic acid. See the difference? A culture maintained firm will give you less sour (and more lift). A firm pre-ferment made from a liquid starter may give you more. The magnitude of the metabolic effects reflect the relative differences in population numbers.


-dw

nicodvb's picture
nicodvb

Hi,
this explanation is very clear! Finally I found what I was searching. The only thing that leaves me some doubt is the "ripeness" of the firm SD: can you elaborate a bit more? I'm still confused on this behalf. I don't know if I'm feeding my starter at the right time because I don't know how to correctly evaluate whether it's the right time or not.

Thanks very much to you and Dan for your precious help!

dghdctr's picture
dghdctr

Nico:



These are 3 different pre-ferments, all more or less at an ideal state of ripeness.  By this I mean that they are ready either for use in a bread dough, or to receive their periodic feeding.  Lower-left is liquid levain at 100% hyd, center is firm levain at 60% hyd, and lower right is poolish.


Notice how the surface of the liquid levain and the firm levain are both starting to recede (collapse) just a bit?  That means they have recently passed the point of maximum expansion, and this is generally viewed as way of judging that a starter is definitely ready.  The poolish was also very close to readiness, and, though it doesn't show signs of receding as much as the levain, my experience in dealing with poolish told me it was OK for use.


You will not always make the right decision about ripeness, but if you're close to the appearance of the above you should be fine in most cases.  Only experience with your own pre-ferments will make you more sure about your decisions.  Just accept that you'll be wrong sometimes and learn from it.


--Dan DiMuzio

nicodvb's picture
nicodvb

It's exactly how I decided when my starter was ready.
Thanks!

ehanner's picture
ehanner

I'm impressed that you were able to time those so well. A very good visual description of the process.


Eric

dghdctr's picture
dghdctr

It's kind of you to say so.  Of course, they were only close to being all precisely ready at the same time -- the poolish was dragging by 15 minutes or more.  I took the shot because the liquid levain, especially, might have dropped completely if I'd waited much longer.


At the time I made this photo, my culinary students were making/refreshing these preferments several times a week, so the timing was more of a "known quantity" from recent experience.  If I had to do the same photo this week, on the other hand, I'd probably have to do some testing for a couple of days to see how all three pre-ferments were reacting to the conditions where I live now.  Only then would I try to ferment them to arrive at the same degree of ripeness at about the same time.


--Dan DiMuzio

Debra Wink's picture
Debra Wink

I'm so glad it was helpful. Dan's photo is a very good guide. The middle shows what my firm starter looks like at feeding time, though I sometimes feed sooner to reduce the sour quicker. If you go much past what the picture shows, especially on a regular basis, the bacteria catch up, and even the firm starter turns sour. Timing is everything  : )

nicodvb's picture
nicodvb

Hi Dan,
your explanation is very clear and very convincing, but as usual it raises another question.
As you said the "madre" is supposed not to be sour at all, becuse the general practice is to tie it tight after a refreshment and make it ferment until it almost bursts (in a sense it actually bursts, literally!), then refresh it 3 times at 4 hour intervals. (what's the correct term for this practice? "tying" doesn't sound good to me.)
I don't know the inner working of the processes involved, I even opened a thread today asking for clarifications. What I'd like to know if this tying causes an increase of the yeasts count or a strengthening of the dough overall, or if it's just a way to reduce fermentation and acidification as someone else told me.
The point I want to get to is this one: I simulated the same procedure on my liquid levain: I filled to the rim a small jar with my sourdough just fed, closed it tight and made it ferment at ~28C for 4 hours. As I expected it opened the top quite violently and overflew ;). Will this procedure strengthen my liquid sourdough? Or do I risk some negative side-effect such as souring?

Thanks,
Nico

dghdctr's picture
dghdctr

Hi again Nico,


I'm really drawing on what I've heard that Italian bakers do with this answer -- I've never wrapped a pre-ferment this way myself.


My understanding is that the firm, barely acidic "madre" is double wrapped to contain its expansion.  The package starts out sort of soft and flexible, but then after fermentation it gets so taut that you can bounce it off any hard surface.  Apparently, that signals to the baker that it is ready to be refreshed.


I'm guessing that this practice pre-dates the modern methods we have to manipulate the rate of fermentation for a pre-ferment.  In the days when you could not control the ambient temperature in your bakery at all, and there was of course no chilled water available to help you get a precise dough temperature, you probably would not feel that a strict "every 4 hours" regimen was safe and predictable enough to rely upon all the time.


You might prefer to react to the needs of the starter as evidenced by physical clues (as we still should, in any case).  Wrapping and tying-off the "madre" in a package allows you to judge its state of "readiness" by how taut the surface is after it has inflated fully.


I put "readiness" in quotation marks because I think that unless the piece of madre was exactly the same size and the package was wrapped at precisely the same size (same level of potential volume), this method might not be very precise.  At the time it was developed, it was probably embraced -- justifiably -- as a simple, practical way to judge the readiness of the madre.  Now that we have the ability to mix with whatever water temperature we choose, or the option of using a warm room or proofer to regulate the growth of the pre-ferment, I don't think that relying on the "tying" method is necessary.  I have no evidence to support my ideas about it, since I've never made any side-by-side comparisons, but I'm still betting that this packaging technique is one of the old practices that has no further practical use.


Of course, from a certain perspective, wood-fired ovens aren't very practical for baking bread anymore, yet some bakers still choose to do so.  I'm pretty convinced that at least the pros who choose to do so love the PROCESS of baking at least as much as the products they can produce.  Using the old methods is a big part of their enjoyment in baking, so it makes sense that they would go to the extra expense or hassle of using a WFO.  Possibly the same sort of reasoning could explain why a bunch of bakers might hold on to any other ancient practice that has little demonstrable effect upon final product quality.


While I might seem dismissive about the technical value of this packaging technique in modern baking, I in no way mean to diminish its value to any baker who wants to use it.  There is an indefinable value to maintaining traditions -- the history that these practices preserve is at least still fascinating, and it might be argued that traditional methods remind us of who we are as bread bakers.


--Dan DiMuzio

Debra Wink's picture
Debra Wink

Sorry Nico, I'm falling behind here. I was working on a response on my desk computer to post this morning, but my husband has it tied up downloading a very large file today. So, it's looking like I may not get it posted until tomorrow.


Your latest question, bringing up the subject of wrapping and tying starters, is something I've written about before. I think Dan is right about the purpose being simply a useful indicator, but it is more about the effect of feeding frequency than hydration. It's all very complicated, having to do with population growth cycles (lag times, growth and stationary phases), and taking advantage of the disparity between yeast and lactobacilli. I'll try to do a better job explaining later, but in the meantime, maybe this will help:


http://www.thefreshloaf.com/node/13525/my-imitation-chad-robertson039s-country-sourdough#comment-83047


-dw

dghdctr's picture
dghdctr

I look forward to reading that thread about . . . .umm . . . bondage? ;-)


Nico -- I just wanted to be clear about what I'd choose to do in your case.


If you're making a lean bread dough, do whatever you want with starter hydration, as long as you keep it healthy and feed it at regular, sensible intervals.  Use or feed the starter when it is ripe, whether or not this happens earlier than expected.


If you're making heavily enriched dough that has to ferment a long time (6-24 hours), the firm starter might be your best bet.  There's less danger of a too-high rate of enzyme activity, which could weaken the structure of a long-fermented loaf.  Also, the slightly higher level of acidity should re-inforce the strength of an otherwise fragile dough like pannetone.


Trying to keep a limit on the expansion of your madre by wrapping it or holding it in a sealed jar is unnecessary, in my opinion.  In fact, while I do cover the container for any pre-ferment, I try to leave some small opening to allow CO2 to escape without blowing off the cover.


That's just what I'd choose to do, and why I would do it.  I'm sure there are other ways of approaching things.


--Dan DiMuzio

Debra Wink's picture
Debra Wink

Starter wrapping (and tying) was one of those seemingly odd practices I was curious about until I figured out the purpose. If you have The Bread Book by Thom Leonard, he has a little pictorial and directions for how to wrap a starter on page 55. Apparently, this is also a traditional method for keeping desem (another non-sour, firm starter). Here's what he wrote:



As the starter ripens, it will stretch against the cloths. If you've folded well, the ball will inflate from the gases of fermentation and blow the package up like an overstuffed pillow. The ball should be hard and the cloth as taut as a drumhead. If the ball is soft, and the top sunken rather than tightly arched, the starter was too warm, left for too long, or wrapped loosely.



Ordinary starters are considered 'ripe' when they've domed and then start to flatten slightly. But for these starters, where sourness is undesirable, the way to keep the bacteria in check (in addition to low hydration) is to always refresh early, while the yeast are still actively increasing, but before the bacteria start to really take off. The package allows for a little expansion, but lets the baker know when it's time to feed again, if he wants to cultivate rising power and repress sourness.


And it works too---I'll vouch for that (early refreshment, that is). But the science behind it will have to wait for another post; I may have to draw some crude diagrams. The good news is, you don't have to keep a starter in bondage to take advantage of early refreshment and frequent feeding. That's really all it's about.


Bread dough is calling  : )
-dw 

Debra Wink's picture
Debra Wink

One bite at a time  : )


I've been putting off this part of the discussion, not only to get past the holidays, but because I really don't know how best to approach it. I've alluded to it, hinted at it, and danced around it, but the elephant isn't getting any smaller.   In the past year, I've introduced Fresh Loafers to a range of interrelated topics on the more technical side of sourdough microbiology, including bioenergetics and metabolite production (here, and here), population dynamics (here, and earlier in this thread). Now it's time to add microbial growth kinetics into the conversation. But, let's take it one bite at a time. Right now, I just want to lay a foundation, and then we can build up from there as time permits.


So, what the heck are microbial growth kinetics? I do have a tendency to pull out the technical terms, don't I? That's okay, I think Loafers can handle it ;-)  Most simply stated, what I'm talking about is the pattern of change in population size, over time. In a sourdough culture, it begins at the time of refreshment. If you plot cell numbers on a graph, using a logarithmic or 'log' scale for the vertical axis, and time along the horizontal, a characteristic pattern forms.


  The curve has four distinct regions, representing the different phases of the population growth cycle.


Lag Phase:  The population size remains about the same during this time. The cells are acquainting themselves with, and adjusting to, the new environmental conditions brought about by refreshment, and they're busy preparing themselves for growth. The length of the lag phase depends in large part on temperature, the inoculum size, and the condition of the cells.


Growth Phase:  Also referred to as the exponential phase or log phase, this is where the population is doubling at regular time intervals.


Stationary Phase:  The stationary phase is brought on by a dwindling food supply and/or the build up of toxic waste products. Energy production becomes less and less efficient as energy needs increase. As in the lag phase, there isn't much change in population size. The cells start initiating physiological and morphological changes to shut down or reduce energy-consuming cellular processes, so that they can conserve themselves and extend this phase as long as possible.


Death Phase:  The cell number starts declining. When the energy demands of survival exceed a cell's energy-producing capacity, it will die.


A word about this and coming diagrams: I don't apply any actual laboratory values to these, because nothing is constant, and everything is variable (which will be more apparent later on). Since you won't be taking cell counts at home, the numbers have little practical value anyway, and tend to be so huge as to be mind-boggling. You can see and taste the effects, which is what really matters. So, my graphs may be exaggerated from what they are in sourdough, because they are general, and meant only to be conceptual, as a visual aid to understanding the dynamic relationships.


Okay, that's a big enough bite for one day  : )
-dw


P.S.  It may be a few weeks before the next installment, and I apologize for my lack of talent in the art of illustration.

Shiao-Ping's picture
Shiao-Ping

... for your excellent explanations in this thread.  Thank you for taking the time to do all the write-ups.  Here at The Fresh Loaf, we are so lucky to have you and Dan to explain to us the mechanics inside the sticky, wobbly mess called starter.  We are so privileged.  THANK YOU.


Shiao-Ping

rick.c's picture
rick.c

I was about 4 or 5 posts up and thought, "Boy, I need a graph."  Imagine my excitement when I saw it was in log scale!!!!  Really, it helps.


Now, if you could draw 12 of them comparing the activity of yeast-vs-acid for dry-wet and hot-cold and lay them out in an array for hot-cold and dry-wet, I could see it all.  No, I'm not asking.


Thank you very much (Debra & Dan) for sharing your knowledge and your patience in doing so.  Off to bioenergetics & metabolite production..


Rick

SylviaH's picture
SylviaH

Plenty enough for today!  Thanks, Debra


Sylvia

Debra Wink's picture
Debra Wink

In my last post, I showed what a general, microbial population growth curve looks like, to introduce some terms and patterns you may or may not be familiar with---lag, growth, stationary and death phases. You may have noticed the similarity between the way the population size increases and decreases, and the actual rise and fall of a freshly fed starter. First, there is stillness for a period of time before you start to see bubbles forming. Then, the bubbles start coming faster and push the starter upward until it peaks, or reaches the highest point that it can. The level may even stay at that point for some time before starting to recede, eventually ending up back at the starting level. So, it's very easy to conclude that one is an indicator of the other, but it's not quite that simple.


While CO2 is one of those metabolic effects I talked about earlier, for which the magnitude is related to population numbers at any given time, it is also related to the condition of the individual cells and the rate at which they are pumping it out. Whenever yeast cells are respiring or fermenting sugars to generate energy, they are producing CO2. So the rate of gas production is a good visual indicator of the overall metabolic activity in the yeast population. But if you've read my post on factors affecting microbial growth, you know that metabolic rate doesn't necessarily correspond to reproductive rate. The yeast may be working hard just to maintain homeostasis, as is the case when waste by-products build to toxic levels, or the temperature rises higher than their comfort zone.


The rise and fall of a starter doesn't pinpoint exactly when yeast stop reproducing, but it does give us a good indication of when the population is most metabolically active---and that is very important. However, a well-kept sourdough starter will never see the death phase, because it will be refreshed well before the population size starts to decline. That's not to say that the starter won't collapse and shrink in volume---that's just metabolic activity and gas production slowing to a hault. Yeast enter the stationary phase when they can no longer produce enough excess energy to reproduce themselves, either because there is no longer enough food to turn into energy, or because the accumulation of waste by-products forces them to use all their energy on survival. But rather than continuing to fight a losing battle, they go into sort of a shut-down mode to turn off energy-consuming cellular processes and conserve themselves for better times.


They start making physiological and biochemical changes that allow them to reduce their energy needs, so that they can suspend their metabolism and remain viable even though sluggish or inactive. The starter may shrink as metabolism slows and production of CO2 comes to a halt, but the population may remain high for some time, declining only slightly for quite a while. For that reason, I am extending the stationary phase indefinitely and adding an overlay of what gas production might look like in relation to population size.


              


Note that while rise and fall in a starter will correspond to rate of CO2 production, the overall expansion is limited by physical properties of flour and hydration. A thick starter with strong gluten can trap and hold onto the gasses more effectively, rising higher, longer. In a thinner starter, bubbles rise to the top and release their gasses into the atmosphere much faster, producing less or no rise, but not because gas production is any less. Only because the gas is percolating through and out of the starter, rather than being held in. The reason it is generally advised to refresh after the starter has peaked and is only beginning to show signs of receding (although there are some exceptions to this), is because that is the point at which you know the yeast population has reached its maximum for that growth cycle, and you want to feed again before the yeast start to shut down. Keeping them active helps build vigor and leavening power.


-dw

nicodvb's picture
nicodvb

Hi Debra,


thi is *very* interesting.


Many recipes for rye breads that I'm preparing recently state to let the poolish collapse completely before preparing the final dough, in order to decrease the PH of the dough. I was just wondering if and how much the yeasts would die during the collapse, as actually the final dough rises as fast as when I used the poolish at the top.


 


Your posts explains very well the effects I'm seeing.


 


Now, is there any way to determine how much of the yeasts population is dormant and how much of it is dead after the collapse?


Thanks for you explanations and for all the time you dedicate us!

Debra Wink's picture
Debra Wink

Hi Nico,


Yep, this is one of those cases where you refreshed at a different point (far right) along the curve to achieve a higher level of acidity, and when I get to adding the lactobacilli into the picture, I think it will all be even clearer. When using the wrapping/tying method we talked about earlier for non-sour firm starters, the refresh point would be somewhat left of where I have marked. So there is some room for adjustment, depending on the desired effect.


I can't give you concrete numbers or times because it depends on various factors, but I doubt there is any significant decline until well beyond the collapse point. And if the starter is healthy and vigorous going into this final build, the population won't even have really shut down yet---first they go into more of a stand-by mode, from which they can resume activity relatively quickly, and that seems to be what your results reflect. There are degrees to the process.


-dw

MezonosMan's picture
MezonosMan

 


    Mrs. Wink (I was taught never to call my teachers bu thier first name)


   Finally finally things are starting to come together love the story building going on.. but of course the suspense is killing me .. love the graphs.. love it all!


  One question (for now) you say that with a wet starter (due to it lack of gluten development) will start to fall before the "stationary phase" - but how is the falling a definitve sign of maximum yeast population as I seem to understand you.


   You can't imagine the joy your clarity brings me... I dont know how I can thank you.


   please keep your posts coming.. I feel like a kid reading a comic book.. geting to the last page every week and reading the words "to be continued".


   Thank you so much.


 -Charlie


 

Debra Wink's picture
Debra Wink

Mrs. Wink was my mother-in-law ;-)



you say that with a wet starter (due to it lack of gluten development) will start to fall before the "stationary phase" - but how is the falling a definitve sign of maximum yeast population



That's not quite what I'm saying there. It's not that a really wet starter will fall sooner, it's that it won't rise as high. Falling shows that the CO2 production is slowing down, which wouldn't happen while the population is dividing at regular intervals, because that requires high metabolic activity. So, it isn't going to fall before the stationary phase (unless the temperature drops). Make sense?


-dw

Yerffej's picture
Yerffej

Fantastic thread.  My thanks to all who are do the asking and answering.


Jeff

JeffOgorzalek's picture
JeffOgorzalek

Also thanks to all for the great discussion.  And to Ms Wink(would that be Dr Wink? and if so, do you still prefer to be addressed by your first name?) - I've enjoyed all the science behind the dough. I believe I read that you prefer a mild sourdough, but my question is - if one wanted to make the sourest sourdough possible, how would one practically implement the factors you've mentioned favoring sourness, in both starter and final dough recipes?


Let me throw out some ideas for maximum sourness,  for your feedback as to whether they would actually further that goal.


- continually stir and oxygenate a very liquid starter, perhaps using an aquarium bubble aerator and magnetic stirrer.


- add fructose and citric acid at each refreshment. (but how much should one add?)


- measure pH in order to time refreshments,  that is, refresh only when pH drops to levels inhibitory to the lactobacilli. (and what level would you recommend?)


- keep temperature between that optimum for the yeast and that optimum for the lactobacilli, perhaps 30 deg C  (so as to promote the lactobaccilli without killing off the yeast)


And then for the final dough, what would be the best ratio of starter to newly added flour/water (for end loaf maximum sourness) if one wanted to bake the same day, that is with perhaps a maximum of 8-10 hrs of incubation from dough mixing to baking.


Please be brutally honest if you think these things would be ineffective or just plain wacky. Can you think of any other factors that could be successfully manipulated in the home?   Thanks again for all your posts.


 


 


 


 


 


 

Debra Wink's picture
Debra Wink

Well, first things first---I must tell you that there are no PhD's hanging on my wall, so we don't need to be too formal here :-)


In a way, I have to disqualify myself from advising too much on how to achieve the sour because my own preferences have kept me from doing a lot of experimenting to that end, which limits my first-hand knowledge in this area. I do gather a lot of feedback from others though, assimilate and reconcile that with my own experience with starters, my background in microbiology, and what I have learned from research literature of the more recent past. There is one area in particular where I think bakers tend to shoot their starters in the foot, and that is trying to get their starters to be what they want their bread to be, without regard to how that effects the desirable organisms and population dynamics. Understanding the post in this first link is key before discussing the specifics in your question:


http://www.thefreshloaf.com/node/15657/sourdough-stages#comment-101215


That said, trying to turn your starter sour and keep it that way will cause you to lose the desirable LAB and possibly your leavening power as well.


- Oxygenation really isn't necessary. I'm guessing your purpose is to increase acetic acid output, but beware that only some LAB can make use of oxygen, some are actually inhibited by it, and acetic acid slows yeast.


http://aem.asm.org/cgi/content/full/64/7/2616/F3   <click to see graph


This and the next graph are from:  Modeling of Growth of Lactobacillus sanfranciscensis and Candidia milleri in Response to Process Parameters of Sourdough Fermentation. Ganzle, Ehmann and Hammes


- Fructose and citric acid increase acetic acid, but again, that is not especially desirable in your mother culture. If you want to experiment with it, save it for the final dough.


- Maintaining the right pH is important to preserving and maintaining the most desirable organisms in your starter. But the most desirable one---Lactobacillus sanfranciscensis---the one found in San Francisco Sourdough, won't survive in a starter that is maintained at a low pH. It's ideal pH is about 5.5, and growth drops off very quickly much below 4.5. The regular, frequent refreshments that keep the yeast active, also help to keep the pH from dropping too low for the most flavorful LAB, so measuring the pH really isn't necessary unless you particularly enjoy doing so. Go for the acid production in the final dough and/or your preferments, but don't make that the goal for your mother culture.


http://aem.asm.org/cgi/content/full/64/7/2616/F2   <click to see graph


- Temperature is tricky. At 30C (86F), the wild yeast will likely disappear, or at least find it very difficult. Their growth rate drops off much quicker in the mid 80's (F) than anywhere in the 70's. Heterofermentative lactobacilli will probably also drop out, and your starter will be more acidic, but without acetic acid. Homofermentative LAB tend to dominate starters maintained that warm. Mid-70's is probably your best bet.


 



Four sourdoughs (A to D) were produced under practical conditions, using a starter obtained from a mixture of three commercially available sourdough starters and baker's yeast. The doughs were continuously propagated until the composition of the microbiota remained stable... The analysis of the starter mixture revealed the presence of Candida humilis, Debaryomyces hansenii, Saccharomyces cerevisiae, and Saccharomyces uvarum... Isolates identified as C. humilis and S. cerevisiae were shown by randomly amplified polymorphic DNA-PCR analysis to originate from the commercial starters and the baker's yeast, respectively.



  • In sourdough A (traditional process with rye flour), C. humilis dominated under the prevailing fermentation conditions.

  • In rye flour sourdoughs B and C, fermented at 30 and 40°C, respectively, S. cerevisiae became predominant in sourdough B, whereas in sourdough C the yeast counts decreased within a few propagation steps below the detection limit.

  • In sourdough D, which corresponded to sourdough C in temperature but was produced with rye bran, Candida krusei became dominant.


http://aem.asm.org/cgi/content/full/69/12/7453/F1   <click to see graphs


The yeast species isolated from the sourdoughs were also detected by PCR-DGGE. However, in the gel, additional bands were visible. Because sequencing of these PCR fragments from the gel failed, cloning experiments with 28S rRNA amplicons obtained from rye flour were performed, which revealed Cladosporium sp., Saccharomyces servazii, S. uvarum, an unculturable ascomycete, Dekkera bruxellensis, Epicoccum nigrum, and S. cerevisiae. The last four species were also detected in sourdoughs A, B, and C.



From:  Identification and Population Dynamics of Yeasts in Sourdough Fermentation Processes...   Meroth, Hammes and Hertel



 


I know this isn't particularly what you wanted to hear, but hopefully I wasn't too brutal :-)  What you need to always keep in mind are the living elements, and how sensitive they are to the way the starter is maintained. Because of the many known and unknown factors involved, living things interact with each other and their environment in dynamic, and sometimes unpredictable ways.


It's just never that simple with living things.


-dw

RobynNZ's picture
RobynNZ

Hi Debra


It's hard to keep up with the all the posts on TFL but I always click on any you have made, even if they are hiding under a simple subject title!  Thank you yet again for a very useful post. I trust others will get to see it too.


Robyn


 

JeffOgorzalek's picture
JeffOgorzalek

Debra,


   Thank you very much for all your comments. I like your idea of keeping the starter under optimum conditions and then experimenting by tweaking some parameters for the final dough. I will report any successes I have or any especially spectacular failures as well.    I'd love to read posts from anyone who has had luck getting a really sour loaf.  I think I remember you commenting on Hamelman's Vermont sourdough, so I might try that recipe also.  Thanks again.

Debra Wink's picture
Debra Wink

Last time, I believe we left off in the stationary phase, which is a good starting point for today's topic. Stationary phase begins when a population can no longer generate enough excess energy to increase in number, and ends (for our purposes) at the time of refreshment. It is brought on by changing conditions in the starter environment---namely, depletion of resources and/or build-up of inhibiting substances. When cells find it increasingly difficult to produce enough energy even to maintain homeostasis, they begin physiological and biochemical changes to slow or turn off energy-consuming processes and conserve themselves for more favorable times. It's not something that happens all at once in sourdough, but a process that proceeds increasingly over time. Think of the stationary phase as a resting phase, where "rest" starts out just dozing off, but progresses over time, into a deep hibernating sleep.

If stationary phase is resting, then lag phase is waking, which must happen before a sleeping population can start growing again. It takes longer to wake up from a deep sleep than from a short nap. And so it is with resting cells. All of the physiological and biochemical changes made to suspend metabolism in the stationary phase, need to be reversed in the lag phase for cells to return to activity, and that takes some time as well. So, how sluggish and dormant the cells become, has an impact on how quickly they can return to their active state. The longer a population remains in stationary phase, the longer the next lag phase will be. That is one reason why you may find that a starter fed once a day or less, doesn't snap to quite as quickly as one fed twice a day or more. Or a starter forgotten in the back of the refrigerator for months can take well over 24 hours to show the first signs of life. But chances are, things are not as dead as they may appear, the organisms need more startup time.

The horizontal axis represents time, the vertical is population size, and the dashed lines represent refreshment points. This diagram is meant to show what happens when stationary phase is prolonged. Note that the next lag phase is much longer. Feeding at the end of growth phase/beginning of stationary phase several times in succession, will help to reduce lag time, and increase vigor.

 

Physiological condition of a cell population is just one factor influencing lag phase. Another is change in the starter environment---in pH, temperature, salinity, gas composition, energy sources and nutrients, inhibiting substances, etc. In general, the bigger the change, the longer the lag time, because there are more internal adjustments a cell must make in response. For example, when hydration is reduced, or salinity increased by the addition of salt to the preferment or dough, a cell must pull in a proportionate amount of compatible solutes from its surroundings to counteract the tendency for water to be drawn out. A change in temperature will require cells to adjust the fatty acid and protein makeup of their membranes. Enough solidity in order to preserve their ordered structure, while at the same time maintaining enough fluidity for nutrients and other substances to pass through. Therefore, saturated and unsaturated fatty acids need to be balanced, and because they change between solid and liquid at different temperatures, the right balance changes with the temperature. As nutrient supplies change, various metabolic pathways are turned on or off by mechanisms that are sensitive to the presence or absence of substances in the cell's environment.

So, a lot goes on inside a cell in preparation for growth---more than I can do justice to. But hopefully this gives a general idea. Point being, that cells must adjust to the degree of change which comes with refreshment. And the thing that most determines the degree of change in the starter environment, is the refreshment rate. By that, I mean the ratio of fresh flour and water to mature starter. The greater the refreshment, the greater the change and the longer the lag time. Also, independent of its potential to change, temperature is an important factor in its own right. All else being equal, lag phase is shorter in warm temperatures and longer in cool.

Well, I don't know about you all, but to me, that feels like about a big enough bite for one day. So, I'll give you some time to digest that before taking on the growth phase---because there might be a little math involved  :-o

Don't worry, it won't be painful :-)
-dw

nicodvb's picture
nicodvb

are always very clear. I'm sure your math won't be scary ;)

nicodvb's picture
nicodvb

welcome back to this new installment, Debra! It's always a  pleasure watching thourgh the magnifying glass you offer to us readers.

As for temperature I noticed that my starters (solid and liquid, refreshed every 24 hours) tend to get pretty warm as fermentation proceeds. I keep them in covered glass jars that in turn stay in a plastic box. I bet that from refreshment time to top rise they gain at least 3-4°C because they are warm to the touch, especially the solid one. My house is always around 23°C. Is this temperature increase excessive or does it fit in a normal state of affairs?

  Nico

Debra Wink's picture
Debra Wink

Hi Nico,

Just doing a little adjusting to realign the image. After referring someone to this thread (an oldie, but a goodie), I noticed the right side was cut off. Things shifted here and there in the site upgrade, and I guess I missed this one.

Microorganisms do generate some heat. How much of it is retained depends on a number of variables, but a 3-4 degree rise isn't outrageous ;-)

Are you ready for panettone season?
dw

nicodvb's picture
nicodvb

Panettones every weeek end, and yes, they are coming out nicely now that I've learned what my little friends like and how to treat the dough.

After all the troubles I had I stabilized on a technique: single dough risen for 4 hours at room temperature, than 2-3-4 days in the fridge and finally the last rise in the mold. Panettones rise hugely and come out soft and aromatic. Dough prepared with this procedure seem to be stabilized during the long cold retardation, even though Janet is scared:)

Using the liquid or the solid starter doesn't make a difference. Maybe the liquid one performs better, but marginally.

I'm relieved to know that my starters don't have fever:))

 

Debra Wink's picture
Debra Wink

I'm not at all surprised you have found a way to make it work on your terms. Just goes to show that understanding what, when, where to apply temperature, and why, is what makes it an effective tool.

You get it  : )

P.S.  You must send me some photos of your panettones during the holidays.

nicodvb's picture
nicodvb

Here are some pictures

http://laconfraternitadellapizza.forumfree.it/?t=67346988    (almost 100% butter)

http://laconfraternitadellapizza.forumfree.it/?t=67466272   (exactly 100% butter)

https://lh4.googleusercontent.com/-k5IHkkkCrS0/UkVhw6OMlVI/AAAAAAAAB6I/BFSLQTDigFw/w640-h480-no/2013-09-27+11.55.00.jpg

As you can see they are all very rich doughs. Recently I stabilized on a "salomonic" recipe: same weight of flour, whole eggs and butter + 50% sugar + 30%starter and 2% salt. The method that changed my experiences from night to day is txfarmer's intensive mixing, but on steroids:). Using the paddle I knead at very high  speed until the dough comes together perfectly. Using whole eggs helped me a lot.

Previously, when I needed gently, egg whites helped my dough come together, but the baked crumb dried out very soon. Using the intensive mixing method the crumb remains perfectly moist as it's desirable, no more dryouts. I guessed that all the energy I use may lead to denaturing of the ovotransferrins that are blamed to squeeze water away when they oagulate during baking. Do you believe it's a plausible explanation?

As you can see I was forced to use much less dough for the mold (800 gr of dough is the ideal amount for a 1 kg mold). Tjis method works so well that in the second case I was able to use 100% durum wheat flour for the dough, a flour that is far from being strong.

  Nico

 

 

Janetcook's picture
Janetcook

Hi Debra,

Thank you so much for picking this up and writing more about what is happening in our starters.  I also really appreciate the diagrams you included.  I find that diagrams stay in my mind  so much better than words so retrieving and understanding the information becomes much easier for my brain 

It is hard to find such easy to read and understand information on the macrobiotic end of baking so I always appreciate anything you contribute here!

Janet

 

Debra Wink's picture
Debra Wink

You're welcome, Janet, and thank you  : )

RobynNZ's picture
RobynNZ

Over the summer/autumn here I have kept my starter on the bench and have been feeding it twice daily and at increased ratio to starter. Your post is a timely reminder as our days begin to cool to review my procedure. It suits me to feed twice daily so I've been planning to lessen the ratio to starter in order to keep the same interval between feeds. I assume by making such changes I'll be altering the population ratios of the various microflora at peak, but I guess that contributes to the never-ending variety that helps maintain my interest in baking sourdough.


At the beginning of the summer I had both a liquid (100%) starter and a firm (60%) starter but found the 100% rather demanding to keep in hot conditions (ie shorter & shorter lag times) and so decided to only keep the firm one and make hydration adjustments during the levain build. However I have kept thinking about what the difference in microflora population must be between well maintained liquid and firm starters and whether I am kidding myself by altering the hydration over a feed or two. Maybe with the cooler weather I'll get two going again and do some experiments to find out what difference there is in flavour and proofing times using a 100% maintained starter and a firm starter converted to 100% hydration over the day before baking.


I'll be interested to hear your comments on the growth phase.


Regards, Robyn

Doc Tracy's picture
Doc Tracy

Please post your results when you find out! I'd be so interested in what you decide after you've done some baking with both a firm and liquid starter that are maintained as such. I've been keeping my starter relatively firm in the fridge and simply converting to what I need in a single build when I bring it out, based on what the recipe calls for. But, in reading Debra's and other poster's stuff, I'm beginning to think I may be falling short of what I could really be experiencing in my breads. Perhaps after the summer here in AZ I'll give it a try myself, maintaining two starters on the counter, rather than in the fridge.


This week I'm going to try doing some multiple builds before baking and see if I note a difference in vigor and taste, both in my rye bread and whole wheat. Not very scientific as we are getting very warm in the RV. Won't be able to do much until I'm back in the house and temperatures fluctuate less.


Just got my grain mill and can't wait to see how my starters respond to fresh grain. I feel like feeding them just to see how they act!!!

Debra Wink's picture
Debra Wink

Last installment, I think I stopped at the influence of temperature on lag time. Temperature also provides a good starting point for the next phase: Growth. Just as temperature plays a big part in the length of the lag phase, it greatly influences growth rate as well---not so much in the final number of organisms, which is limited more by other things, but in the generation time (how long it takes a population to double). The closer the temperature is to optimal for a species, the faster its population will increase. This goes for the other factors as well---pH, water activity, food sources, inhibiting substances, etc.---the closer everything is to optimal, the faster the organisms will reproduce.


Whereas the stationary and lag phases represent times of little to no net change in population size, the growth phase is where cells are metabolizing sugars at a relatively high rate, and the population is doubling at regular intervals. But the threshold between lag phase and growth is not a sharp one, as in going from 0 to full speed at a specific point. There are no sharp angles on a population growth curve. There is a ramping up, especially during that first generation as the cells get going in the transition from lag to exponential growth. So, the first doubling is generally the slowest, and then the generation time decreases as long as conditions remain favorable and there are enough resources to continue growing. Similarly, at the top there will be a slowing in the last generation as the population transitions from growth back into stationary phase. So, generation time in the growth phase is influenced to some extent, by the number of generations in between the low and the high. The population increases fastest, somewhere in the middle. How can you tell how many generations that is? Your refreshment rate will give you a pretty good idea.


If you maintain your culture in a consistent manner, it settles into its own equilibrium. The organisms tend to reach about the same count in about the same time, in about the same ratio to each other when feeding follows about the same rate and frequency each time, with the same flour and hydration, at the same temperature. Changing any of those factors can shift the equilibrium, but the microorganisms will shift and adjust until they find a new equilibrium, which will once again remain steady so long as the maintenance routine remains steady. Whew! That almost sounds like a legal disclaimer, doesn't it? Since the populations are reaching essentially the same highs and lows before and after feeding (in a stable culture, maintained stably), we can draw the connection between refreshment rate, which is a dilution factor, and the number of generations your culture grows between refreshments. You can figure this out quickly from a ratio, a baker's formula, or actual weights, simply by adding up the starter, flour and water, and dividing the total by the starter amount. 



Note that even though 16x is a very large dilution, it represents only one more generation time than 8x. And that generation time will be added in the middle of the steepest part of the growth curve where reproduction is happening the fastest. So, even though the lag time will be a bit longer when making big refreshments, don't expect the ripening time overall to increase by the same factor as the refreshment rate. For this reason, I find it much more useful to think about starter feeding in terms of dilution factors and generations, than in baker's percents or weights.


Well, I think that about finishes the ground level :-)  Next time we'll build up from there, integrating the LAB to see how they relate to yeast and to starter maintenance.


-dw

nicodvb's picture
nicodvb

Hi Debra,


very nice reading once again.


I have a question about the generations count: does your schema apply when the hydratation is much more than 1, say 2.5? For example, if I used a refreshment rate at 250% hydratation would I  get something like 1:5:2 = 8x  accounting for three generations? I mean, wouldn't such a big dilution in so much water with so little flour  affect the count of micro-organisms?


 


Thanks as usual,


  Nico


 


 

Debra Wink's picture
Debra Wink

Hi Nico,


Yes, it works at any hydration (so long as the starter is stable in that feeding regime), because your starter is at the same hydration as the refreshment. It's all about proportion. If/when you're changing hydrations, then the above doesn't really apply until the starter has readjusted and become stable again. There will be a transition period whenever you change something (hydration, temperature, refreshment rate, frequency, etc.). That's why I stressed a stable culture, maintained stably. We're only talking about routine (and consistent) starter maintenance here, not making preferments or dough, where the proportions are different, or salt is added.


And, yes. Hydration will have an effect on the microorganism count (I'll get to that later), but we aren't looking at absolute counts just yet. Only relative values, and how they relate to population growth patterns. This is about the factor of change and number of generations between the low and the high, not the actual low and high values. Hopefully, it will all come together in the end. There really is a method to my madness ;-)


-dw

ananda's picture
ananda

Hi Debbie,


Continued, and many thanks for posting all this incredibly complex information about natural yeast and LAB.   I am, for one, very appreciative; though I'm sure I speak for many.


We [Nico was involved in this as well] have been discussing  a problem apparently arising from excessive and rapid proteolysis in dough.   We were unable to reach a definitive conclusion on the effect of temperature on enzymatic reactions.   Nico was under the impression that refrigeration would not slow down enzymatic reaction.   The small amount of trawling through academic work which I have done suggests that the cold climate does indeed slow down rate of reaction.   Are you able to impart any of your scientific wisdom to this debate please?


For the full post, if you haven't seen it, you can fid it here: http://www.thefreshloaf.com/node/18144/sourdough-loosing-elasticity-please-help


Thanks again


Andy

Debra Wink's picture
Debra Wink

Hi Andy,


Maybe SteveB would care to comment about the effect of temperature on enzymatic reactions. He is our resident chemist :-)  But, after reading through the thread, I don't believe that proteolytic enzymes are the poster's problem. I should take care of business here in this thread first, then I'll work my way over there.


Until then ...

RobynNZ's picture
RobynNZ

Hi Debra


Thanks for the latest installment.  I continue to regret that they are hidden on a thread, which longer term will make it harder to retrieve from archives. Would you consider collating them in a post on your TFL blog sometime.....


I'm afraid I haven't been able to infer what you mean in practical terms when you state:



I find it much more useful to think about starter feeding in terms of dilution factors and generations, than in baker's percents or weights.



When you feed your starter, with these thoughts in mind, what are you seeking to achieve? What do you actually do to achieve this?


Hammelman teaches us to focus on starter peaking.  I established my starter in spring (using the PJ method you have brought to our attention), over the summer and autumn we had reasonably consistent temperatures so I had  the 'stable culture maintained stably' to which you refer. Now winter has begun, with  the change of temperature, the time til peak has increased. While I have now moved it from the counter to the hot water cupboard, the timing to peak isn't as practical as I had been experiencing. I'd been able to feed (1:3:5) a 60% starter twice a day (12 hourly). I have been considering experimenting with decreasing the feeding ratio in the hope of getting back to the more easily managed 12 hour interval (I did also have a 100% starter but gave it up over summer as it was peaking in less than 12 hours and as I did get the firm starter stable, I didn't spend the time working out a maintenace programme for the liquid one - the reverse of my current predicament). The temperatures will continue to get colder, my home is not centrally heated, and even the environs of the hot water cupboard will get colder, esp overnight.(I have also thought that perhaps  I should consider trying a larger feeding ratio and changing to once a day feeding)... 


My question is, if I were instead  to think 'in terms of dilution factors and generations' as I seek a practical maintenance schedule over winter (which may need to be altered more than once),  what would I then proceed to do in practical terms? (And presumably reverse at year-end as temperature head back up again)


With kind regards, Robyn


PS I am concious I am asking a question about firm starter on a 'very liquid sourdough' thread!

Debra Wink's picture
Debra Wink


I continue to regret that they are hidden on a thread, which longer term will make it harder to retrieve from archives. Would you consider collating them in a post on your TFL blog sometime.....



Since the questions were asked in this thread, and it's where the discussion unfolded, I would prefer to keep it here, all together, rather than to break the continuity. That is... as long as that's okay with Nico.


But it's easy enough to keep track of threads here at TFL just by adding them to your favorites, or subscribing to the ones that interest you so that you'll get an email notification whenever there's new activity. Either way, you can have easy access to them at any time through your account. If it's the thread title that bothers you, maybe you can talk Nico into changing it at some point to better reflect the overall subject matter.


I probably will pull this all together and polish it up at some point, but I need to finish it first. You guys are my guinea pigs ;-)  Let's just hope I'm successful.



"I find it much more useful to think about starter feeding in terms of dilution factors and generations, than in baker's percents or weights."



I just meant that it's not so obvious when looking at a refreshment formula in baker's percentages or weights, how much your culture is actually increasing, and what impact the feeding rate has on the populations. The number of generations is a useful piece of information in understanding population dynamics.



When you feed your starter, with these thoughts in mind, what are you seeking to achieve?



Ahhh, good question. But that's a topic for a future installment :-)



Hammelman teaches us to focus on starter peaking.



As do I. Looking at the dilution rate or number of generations doesn't change that.


Go ahead and play with your feeding ratio, and if you don't like the results, then we can probably find something to adjust :-)


-dw


 

RobynNZ's picture
RobynNZ

Hi Debra


I do however rush to say, it's not for me that I expressed concerned about the location of your very useful material, on the contrary, I'm fortunate enough to know where it is; it's for others in the future who may not find their way to this thread. With so much material on TFL it takes skill to use the search box effectively. I am glad to hear that you will consider bringing it all together. Perhaps it may be as simple as leaving a link to this thread on your blog. I have really appreciated your contributions in this thread and I'm sure others in the future will too, if they can locate it.


I did know what your response regarding my starter would be :-). But did hope a different angle to think from, might help me overcome my hesitancy to make changes to my feeding programme. I've decided I'll keep some going as it is, until I come up with a stable system using a different feeding ratio which suits me in terms of both timing and final product. Whilst I would like a routine that is more manageable time-wise, the various breads made with the current regime's starter have been great. Guess there's only one way to find out what  will happen to my bread when I start making changes!


Again, thank you for your generosity,


Robyn


 

venkitac's picture
venkitac

Thanks, Debra and Dan! This thread is amazing, I've never had more satisfactory explanations of sourdough (other than from Debra and Dan in the past, when I managed to destroy a whole wheat bread by retarding it).

a1usteuton's picture
a1usteuton

Dr. Debra,


Your blog has been most informative on the subject of yeast cycles and characteristics, but I am hearing a background of yeast personification as if the yeast anticipates and goes dormant, etc.  Is yeast indeed sentient?  I have always taken the view that lower life forms are opportunistic in action/reaction and that anything remotely governing the apparent thinking process was just an opportunistic response.  This probably doesn't answer the lag or stationary portion of the cycle, but couldn't that be due to an intrinsic time delay response in the yeast or the geometric growth pattern regenerating/subsiding?


Also, in the graph above that showed the feeding cycles of the starter, wouldn't the graph be additive in the vertical minus the net effect of deaths in the colony?  If so, would the second cycle be higher and the third higher yet assuming greater than necessary food resources at each feeding until limits are reached?


With greatest respect,


Jon

silkenpaw's picture
silkenpaw

Jon


I was thinking the same thing until I realised that you are dropping the population by dilution when you feed the starter.

Debra Wink's picture
Debra Wink

Hello Jon,


Microorganisms are indeed responsive, however not through any sort of awareness or planning on their part. They don't think or anticipate, nor do they look for opportunities. But it is the presence or absence of various substances or conditons in a cell's environment that initiates biochemical reactions, turning on (or off) the appropriate metabolic pathways and life processes for whatever the present conditions. That is what is meant by a cell's sensing. A stimulus-response. It's based in biochemistry rather than awareness. The mechanisms are complex and programmed genetically, but the responses are automatic.



wouldn't the graph be additive in the vertical minus the net effect of deaths



As Silkenpaw pointed out, you are reducing the population through dilution. For example, if you are feeding at a rate of 1:2:2, you effectively thin out 4/5 of the population. The remaining 1/5 will regenerate back up to roughly the same density it was before diluting. Each time you thin, it regenerates.


Best regards,
dw


P.S.  A sourdough starter isn't a colony (which is something else entirely). These are very much mixed cultures. I'm making note of it not to pick on you, but because I'm seeing a lot of people misusing the term.

Father Raphael's picture
Father Raphael

1) I bake almost every day but occasionally skip a day.  If I feed my sourdough starter at the end of a baking day, will it be ready in morning or will it have gone past the optimal time to use it? 

2) If I bake on Monday and feed the starter at the end of the day but don't bake until Wednesday, should I have fed it again on Tuesday?

 

rjstucker's picture
rjstucker

Debra, I'm coming to this several years removed from the last comment, but your posts have been extremely helpful in allowing me to be much more comfortable with the whole process.

Thank you!