The Fresh Loaf

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understanding feeding ratios and timings - what are the principles of a starter's growth?

Spikes's picture

understanding feeding ratios and timings - what are the principles of a starter's growth?

Dear all,

I've been reading up to try and understand the behavior of my starter, but I'm still largely confused, especially given the large number of different feeding routines and ratios.

So if you can, please indulge me in this story for a second and point out what I'm missing/got wrong.

When flour and water are mixed they will collect bacteria along the way from the environment (or things added to the mix like pineapple juice of fruit skins) and start to build yeasts and lactobacillus. In the process CO2 will be produced, a tangy taste will be developed and another bunch of chemical processes will happen, but the CO2 and the taste are what I am, maybe ignorantly, most concerned about.

Most schedules to create a starter I've seen involve the same 3 steps:

- add flour + water, stir

- some time later, often 24hrs, take some out and add more flour/water

I really disliked all the throwing away and I couldn't bear to also work out baking discards, so I didn't do anything until I found someone who simply added 20g/20g FW every day for 7 days or so and, surprise surprise, in a week I got a starter going that would double in ~6hrs.

Already there I was pretty confused: why is the entire world throwing away all that flour when just adding a little bit a a time works just fine?

One thought is that maybe that starter wasn't so great and that was partly the reason of a my not so great raising, but that's for another post.

And what's up with this magical 24hrs?

Then it comes to maintenance/feeding schedule: in principle the idea is very simple I know, those bacterias become hungry once they're done eating all the flour and need more or they'll starve. But why are we sometimes feeding it 1:1:1 ratio rather than 1:5:5? or 1:2:2? what's the point of different proportions?

Is more flour going to last longer slowing the raise period? This makes no sense if doubling is the point, because if the yeast ate even half of it, or its equal in weight, it would cause probably enough raise to look doubled. Or is it that since there's more flour more bacteria are attracted into the mix because of the surplus, making the starter stronger?

To make matter more complicated there's also the idea of mixing an already raised starter for a second raise. Yeast being stationary it may not be able to reach all the flour that was added, especially if the ratio was some crazy 1:10:10, and indeed I got an incredible 2nd raise when I did this myself. Is this indeed making my culture stronger since I don't dilute the mix with more flour/water and if so why isn't it a basic step in all those feeding schedules or even levain build-up processes? 

And when it comes to strength, why isn't a crazy ration such as 1:10:10 just gonna dilute the starter and make it weak?

thank you so much if you got all the way here I look forward to your insights and be a little less ignorant about sourdough starter.


phaz's picture

When you don't know how to do something these days, you get on YouTube and look for instruction. Most of those instructions are based on 1 theory that everyone jumps on and repeats, over and over again. A basic marketing tactic is you repeat something often enough and folks will start to believe it. Not that it won't work, but it may not be the most efficient way to go about something. 

Nothing magical in the first 24 hrs, just the start of a process. Bugs are populating, not the bugs we want, but things are happening - an environment is beginning to form that will benefit the good bugs (labs) and good fungus (yeast). Just go with it, it'll figure itself out in time.

More food lasts longer - ie you don't have to feed as often. Bugs can come from both environment and flour. Once a starter is active it has to eat, just like us, so we add more flour. This can add more bugs, but is more about having and keeping healthy bugs, which will be strong and will reproduce.

Why isn't stirring considered a necessary step - no-one thought of it - and no-one took the time to experiment - except me of course. And you don't really need to, it doesn't hurt, and can give some interesting data.

High feed ratios will dilute the starter - and here's the rub - for a period of time. How long depends on how healthy and active a starter is. Yes, you can feed a 111 ratio - if you want to feed 2-3 times a day. Now I'm all about efficiency, I'm also a lazy sot who spends 8+ hrs a day at the golf course and like most busy people don't have or want to spend that much time adding flour to a jar, so we add a lot every few days. The bugs will eat, grow, and populate however much food is added - just a matter of when it'll use up all that food - which brings us to the fridge where cool temps slow everything down allowing a feed to last much much longer (hint hint).

Don't take this the wrong way, but I read this and just see a lack of understanding about a starter - what it is and does. Here's the skinny - a starter is a medium which contain bugs (lab) and fungus (yeast). Our friends are live and need food to live and reproduce. We add food (flour - and other things in some cases) to keep them happy ie alive and uh ready to reproduce. 

Last - this process tends to only be as complicated as you make it and as I like to say - there's never a need to make things any more complicated than they already are. The KISS principle goes a long way in bread making. And I gotta go hit a few hundred golf balls! Enjoy!

Ps - I'm sure you'll have a lot more questions so keep them here. The replies may become good references.

Spikes's picture

thanks Phaz, good insights from experienced people are never to be taken the wrong way in my book. And for sure I have a lack of understanding of starters, that's the whole point of the initial post, along with a desire to understand the principles to not be another bot following instructions without understanding what's going on.

So thank you for all the insights.

Two follow up questions:

1) you mentioned a "healthy and active starter" - what does make a starter healthy and active? its concentration of lab and yeast? How is that increased? feeing alone obviously dilutes the population. By logic it'd seem you'd have to wait for the bugs to have eaten all they can reach, then stir, then feed again. Larger amounts of food would also seem to require more stirring for redistribution, not just let it go for longer, yes?

2) I'd love to feed once a day, how do I know what's the correct ratio to last me 24hrs? I assume there's something I can check to see if a starter is hungry (maybe the alcohol smell?) and feed more the next day maybe until I feel enough that it won't smell within 24hrs. Or, like you mentioned, I could use the fridge. But for how long? when people use the fridge, say in a weekly baking schedule, they seem to get the starter out on a thursday and bake on saturday, meaning 2 days. Also of course that will also change with kitchen's temp (it's 30C/86F here now). Would I just have to try, say put it in the fridge for 5hrs, and see what happens?

I, just in case it comes up, I want to avoid wasting stuff (or baking with discards), so feeding huge amounts to then discard most of it is a no go for me.

thanks again for all the insights.

Mr Immortal's picture
Mr Immortal

There are a lot of variables involved in answering your questions.  How often do you plan to bake bread?  How much starter does the recipe you will be using call for?


If your plan is to bake every day, then maintaining just enough starter to do that will be no problem, you just simply make enough (using your chosen ratio) to give you the amount required for your recipe plus the appropriate amount to re-make your next day’s starter.  But if you are planning to bake once per week, without a discard your starter will grow exponentially with each day’s feeding.  The answer here would be to start out with an extraordinarily small amount of starter, and add to it each day (maintaining the chosen ratio, of course).  This can be made difficult by the fact that most standard digital kitchen scales are not very accurate below 5 or 10 grams.  In this case, the fridge is a better option.  Keeping it smallish, feed it once, allow it to start to rise, and put it in the fridge.  The yeasts and LABs stay healthy, the colder temps just slow them down, but they will perk back up when returned to room temperature after a feeding or two.  It would be during this feeding or two that you would bulk up the amount to make enough for your recipe (with enough left over to have some left to feed and put back in the fridge).


Unfortunately, a lot of the answers you seek, such as ratios and refrigerator times, are going to require some good old fashioned trial and error.  For feedings, I don’t think it’s absolutely critical to feed your starter the very minute it becomes hungry.  Once the starter is healthy and active, it gives you a lot of leeway on your timings.  Personally, I use a 1:2:2 ratio (10g starter: 20g water: 20g flour).  I feed it in the morning, I stir it in the evening, and it seems to be doing just fine with that.


So...  just out of curiosity, why are you not interested in using discard for other recipes?

Spikes's picture

fair enough, just like the point about magic, I appreciate there might be too many variables to give any accurate answer on paper, no problem.

I've been baking daily for the extra exercise, when I start something new I try to do as much as I can of it and then scale down. Ultimately I think weekly bake would be more sustainable, but for now baking daily is what I'm doing.

As to the recipe, I'm using 20% starter, 100g to 450g flour (500-50 from the starter). I normally feed it in the evening to be ready mid morning, altho this has been really confusing as I was working off of this idea of "doubling in 8hrs", but I'm realizing that's really nonsense and it depends on the ratio and the temperature, and how active the starter is. I still don't quite understand how to gauge a starter's population size, but I'm more aware of how changing the ratios alone has brought me closer to have a peaking starter after 12hrs, which is what I need.

I now have two questions, one of which your partially already responded to:

1) how much room for error I have in terms of using a starter when peaked? this morning I put some tape on the jar at 6am, it was about tripled and still had a dome, then went out for a walk. When I came back 2hrs later the starter was deflated. Is it still good to use? it could have deflated right after I left and been "2 hrs past the peak".

2) normally I feed the starter in the evening for the morning, but that means that I'm gonna have 10g leftover starter for 12 hrs, that sounds a bad thing, but I can't figure out how bad it is and I don't know how to fix other than feeding it twice, which would mean more discard in the evening, or stick it in the fridge, which I'm unclear how it can be used for a daily baking cycle (seems most ppl use the fridge for weekly baking cycles).

as to your question about using discards for other recipes, just a matter of time and mental space, nothing against it, I just feel I can't handle that as well right now (learning new recipes, the extra time to bake/cook them, etc).

thanks and take care,

Mr Immortal's picture
Mr Immortal

Good morning, Spikes!


Just a few things to remember in regards to sourdough baking:  people have been doing it successfully for thousands of years.  They were doing it long before the advent of kitchen scales, or modern clocks, or temperature controlled ovens, or calibrated measuring spoons.  They were doing it long before baking calculators and internet recipe videos.  They were doing it long before the knowledge of protein contents or microorganisms even existed.  There is a wealth of knowledge and technology that we have access to that they didn’t, almost none of which is absolutely necessary to turn out sourdough bread.  Granted, the knowledge and technology are quite delightful to have at our disposal and I, for one, have absolutely no intention of giving any of it up.  But I do sometimes think that the knowledge and technology help us overcomplicate things a bit.  We tend to conflate “success” with “optimal”, when the reality is that many perfectly good loaves of bread didn’t bulk ferment in exactly the right amount of time.

On the subject of doubling:  I’ve seen this written elsewhere, but I think a lot of people have a mistaken impression of what is meant when the instructions say that a starter is ready when it doubles.  I think of doubling as an overall benchmark of a starter’s strength, rather than as a measure of its day-to-day readiness.  Rather than reading it as “after feeding it, your starter isn’t ready to use until it has doubled”, the instructions should say “a starter has reached the point where it can reliably raise bread when it becomes capable of at least doubling in bulk on a routine basis after It has been fed.“

A starter’s ability to double is an indicator that the starter is able to make bread.  How quickly a starter is able to double is an indicator of it’s strength and overall health.

Now, keep in mind that doubling for a starter and doubling during bulk ferment or proofing are two different things.  In this case, you are actually looking for the dough to actually double, and the bread won’t turn out at its absolute best if it doesn’t.  If your recipe does call for doubling within a certain time-frame during BF or proofing, it’s basically saying “at optimal temperature, under optimal conditions, with an optimal level of starter strength, this doubling step should take (x) time.”  There is a certain amount of elasticity in these type of directions, in that if one variable is slightly off (for example, temperature slightly low), we can counteract this by altering another variable (increasing time), in order to get the doubling we need.  Ultimately, this is where practice comes into play.  The more often you do it, the more adept you become at reading the relationships between all of these variables.  

Benito has written an excellent tip for being able to gauge when your bulk ferment has reached whatever percentage of rise your recipe calls for.  Use an aliquot jar (any smallish narrow straight sided vessel will work).  Place a small amount of dough in the jar (or juice cup, or prescription bottle, etc.), press it down flat, mark its height, and keep it near where your dough is bulk fermenting.  When the dough in the jar has doubled, the dough in your mixing bowl has also doubled.


So now for your questions.  I’m going to attempt to answer both of them by proposing an experiment:

  1. Take the 10g of leftover starter, and place it in a different jar.  This will be your test sample
  2. Feed your original starter (your control sample) as usual, but skip feeding the test sample.  This will place your test sample firmly past its peak prior to the next step.
  3. During your next scheduled feeding, feed both samples.  
  4. Check them at regular intervals, and note any difference in how long it takes each to double, or to peak, whichever comes first.  Also note any difference in how much rise is accomplished by each.

This test should give you a reasonable idea of how a “past it’s peak” starter will behave.  

For the record, just a few days ago I actually skipped Randolph’s normal morning feeding.  I was busy with other projects, so I just gave him a stir.  That evening, I wasn’t feeling it, being dog-tired, so I just stirred him again.  I did notice that after the third stir, I didn’t get much of a rise.  To clarify, I fed him, did 3 stirs roughly 12 hours apart, and fed him 48 hours after the previous feeding.  After this feeding, I saw no appreciable difference in how much he raised or how long it took him to do it (in relation to how he acts when fed as normal).  I wouldn’t recommend this on any sort of normal basis, as I think doing this long term would be detrimental to a starter’s overall health.  But it kind of indicates to me that a “past it’s prime” starter, if otherwise strong and healthy, can bounce back pretty quickly.  I have to think that a starter that’s only just a little bit past it’s prime would have a negligible effect on the timing of a bulk ferment.


Mr Immortal's picture
Mr Immortal

Hi, Spikes!


Im not a scientist, and I’m relatively new to sourdough baking myself.  I imagine that there are better and more complete or correct answers to be had from some of the others, but I’ll give it a shot:


Many forms of yeast and bacteria are present in flour. More specifically, many forms of yeast and bacteria are present everywhere, on every surface and every living thing.  These microorganisms are mostly dormant, just waiting for conditions to be right to spring forth and start multiplying.  Very few, if any, come out of the air in a starter’s surroundings.  One of the reasons that this process tends to work with unbleached whole grain flours is that they have not had these microorganisms stripped away with their outer layers (the bran) or with chemical treatment. 

When you initially mix flour and water, the first microorganisms to become active are the ones who can tolerate that particular environment.  Now, in the beginning the environment you’ve created (depending on your water source) has a fairly neutral pH.  The bacteria that become active at this point are not the ones we are looking for.  They can include some pretty nasty actors.  But while it sounds like a bad thing that these potentially harmful bacteria are reviving and forming a population in our starter, they provide a valuable function: their byproducts are acidic, lowering the pH of the mix.  (Debra Wink’s article, “The Pineapple Juice Solution”, explains this in great detail.  The Pineapple Juice Solution itself is a method she and her testers created that bypasses the first few days of the process by starting off with a reduced pH environment.)

Every microorganism has a range of pH at which they will become active.  The lowering of the pH level by the not-so pleasant bacteria actually paves the way for other, less unpleasant bacteria to become active.  And again, these new bacteria’s biological functions serve to further acidify the mix.  Eventually, the acidity drops low enough that the initial batch of “bad” bacteria can no longer survive, and it’s right about this point that the pH has dropped sufficiently enough to allow our wee yeastie friends (which have been present but dormant all along) to become active.


At this point, you now have beneficial bacteria and wild yeast active in your starter.  Rather than fighting each other for resources, they co-exist in a symbiotic relationship.  Each helps to maintain the proper environment for the other.  They create a balance.


This balance is what we are maintaining with a regular feeding schedule, and what we are tweaking by making adjustments to that schedule.  When we allow the starter to go beyond it’s peak, we are allowing the yeasts to become less active (they are not dying off... it takes a hell of a lot more than just a late feeding to do that!) and the acid-producing bacteria (lactic and acetic) to flourish.  For some, it’s this extra acidity that they’re looking for (it is the “sour” in sourdough, after all).  This increased acidity also protects their environment from being encroached upon by less favorable microorganisms while the yeasts are “napping”.  (I think it’s also a possibility that this change in acidity helps toggle the yeast’s activity between consumption and reproduction.)


As for discarding: I don’t like it, either.  But in the beginning it’s necessary not only to help reduce populations of potentially harmful bacteria, but also to prevent accumulating a mountain of unusable starter (the process can take weeks to produce a reliably usable starter, so the starter’s size can really add up).  Simply adding the same small amount of flour and water every day can have detrimental effects, due to the fact that you are changing the ratio (which force more yeasts to have to share smaller and smaller food sources, actually slowing down the process).  The discard can’t be used before the starter is mature, so throwing away 20 grams each day winds up being less waste than having to throw away 2 pounds at the end of the week.  Once the starter matures, then any discard goes into a jar in the fridge to be used in other recipes (I made Whole Wheat Sourdough Buttermilk waffles yesterday morning, and they were delightful!). Of course, if you’re baking bread every day your “discard” will actually be what you use in your bread baking.

I think for most bakers, the idea of a 24 hour feeding schedule is simply one of convenience.  Differing feed ratios are a way for people to tweak a starter’s biological clock to fit into their human mechanical clock-based schedule.  Ratios like 1:5:5 and 1:10:10 are useful for increasing the time it takes before the starter must be refreshed, and it does this specifically because it distributes a smaller amount of yeasts into a larger amount of foodstuffs (while the yeasts do not swim around looking for food to process, they do spread throughout the mix by reproducing, which takes time). The greater the ratio of food to starter, the longer it takes the yeasts to spread through the mix.  But I think that a part of this topic that isn’t mentioned often enough (not that I’ve read, at least), is that the yeasts in a starter need to be strong, vibrant, and active before changing the ratio does any good.  If properly mixed, you have seeded a small but strong inoculation of starter throughout the 1:10:10 mix, and given enough time this small amount of yeast will populate the entire mix.  You only actually dilute/diminish the strength of the starter if you re-feed it again before it’s had a chance to repopulate the previous mix.


The idea of giving a starter a mid-schedule stir is something I had seen mentioned a time or two, but had never seen much detail regarding it.  Figuring out the benefits of it required a bit of a leap in logical deduction.  In regular bread baking, your dough rises, you knock it back, and it rises again.  It does this because the act of punching it down redistributes the yeasts and the food sources.  It just stands to reason that stirring a sourdough starter reacts on the same principle.  I don’t really have any actual scientific knowledge of what is happening during this process, or how it really effects the long-term balance of yeasts and lactic (or acetic) acid producing bacteria, I only have my observations of how my starter has reacted to stirring so far, along with bits and pieces of information I’ve gathered through reading many posts from bakers much more experienced than I am.


And this is the part where I’m sure it seems confusing as hell:  How can it be possible for both of those two topics to be true?  Either the yeasts spread through the mix by reproduction, or you have to stir the starter to redistribute the yeast?!?   Again this boils down to the yeast/acid balance.  My understanding (and more experienced members are welcome to correct me if I have this wrong) is that the amount (and type) of acid present controls not only how quickly the yeast reproduce, but also whether the yeasts are optimized for consumption (creating CO2) or reproduction.  And in turn, the rate at which yeasts either reproduce or produce CO2 has a direct effect on the amount (and type) of acid producing bacteria are present.  This is why a starter can both rise to a certain point and then fall (even though it hasn’t completely consumed all of the food source), and populate itself throughout the entirety of a larger food source.


I’m sure that a lot of this still seems like voodoo magic.  It seems like the answer to every question is “As long as you’re doing it right, there’s no wrong way to do it”.  There are a bazillion different methods, and three bazillion different opinions about those methods, but somehow there only seem to be about 132 wrong answers.  Ultimately, what is most important is that you get to know your starter.  Observe how it reacts to the schedule you set, in the environment in which it lives.  Only make changes one at a time, so that you can tell what works and what doesn’t.  Pick a method and stick with it, as long as you are getting the results you want, and tweak things if you are not.  Bake with it, and pay attention to any issues that you can improve upon the next time around.  You will have both successes and failures along the way.  All of the successes and most of the failures will be edible, but the ones that aren’t will make you realize (as you’re chucking it into the bin) that the small amount of discard waste in the beginning was chump-change.  

In the end, how it tastes and how it feels is more important than how it was created and how it was maintained.




Mr Immortal's picture
Mr Immortal

(Just to be clear, I’ve been working on this post off and on all morning, and didn’t see your next post before I hit “Save”)

Spikes's picture

I very much thank you sir for all the time and knowledge you poured into this, it's humbling.

I've read through it and I'm gonna let it sit, this was definitely a 1:100:100 feed ratio for my poor brain :P

And to your very last point about magic, the more disciplines I mess with, the more that holds true, but that's also the beauty of it and why it's an art. Ultimately I find that understanding the principles is as key as developing an instinctive and gut connection to the elements one is working with. It was true of wood and clay, I'm sure it's dough too, it'll just take some time as it did for the others. Glad to have the support of people like you in the process.