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WHY? Change in flour fed to starter yeilds dead starter after 10 weeks

subfuscpersona's picture

WHY? Change in flour fed to starter yeilds dead starter after 10 weeks

I've maintaned a 100% hydration sourdough starter fed with Gold Medal bread flour for 3 yrs. I bake several sourdough loaves once a week and keep about 50 grams in reserve (in a glass jar in the frig) between bakings. The starter has always been reliable and doubles in 7-8 hours after feeding. The starter is used in sourdough breads that typically contain about 30% whole grain flour (where 30% is the percent of the total flour weight). I home-mill all my whole grain flour and mostly use organic hard wheat (either hard red winter wheat or hard white spring wheat) and organic rye grain for the flour.

This summer I decided to transition my starter from white flour only to a white flour and whole grain mix - specifically 50% white bread flour (same brand), 40% home milled organic whole wheat flour (milled from organic hard red winter wheat) and 10% home milled organic rye flour (milled from organic rye). I gradually changed the flour mix over a period of 6 weeks, reducing the amount of white flour slightly each feeding until I reached the new proportions. The "new" starter, once established, seemed stable. It doubled after feeding slightly faster (maybe an hour less - which I attribute to the rye) but worked as usual in the standard sourdough formula I routinely use.

However, after working fine for about 6 weeks, the starter began to fail. It gradually became less active (taking longer to double after feeding), then seemed to thin out, Finally, it refused to rise at all.

I always weigh the water and flour that I feed the starter (100% hydration) and I also weigh the flours that are mixed & used to feed the starter, so the proportions are accurate. The water I use has not changed. The bread formula have not changed (they are tried-n-true recipes I've used many times).

What has happened? I am careful to wash my starter jar well so it is clean when I use it to store my reserve (taken from the mature sourdough after it has been fed and doubled). Except for the change in flour compositon for feeding, nothing has changed (as far as I can tell). Anyone care to speculate?

Thanks in advance to all who reply... SF

Mini Oven's picture
Mini Oven

did you also increase the portion of starter to flour or reduce the amount of flour to starter to make up for slower yeast growth?  Or before refrigeration, leave the starter on the counter longer before cooling it down in the fridge?  

Temperature could have slowed it down and if you waited to "double" the size of the starter before feeding, it is possible you might not have waited long enough.  Always let it reach "peak" or maximum height before feeding guarantees that you don't get caught off guard in the fall or when seasons start to change to cool nights.  Just letting the starter run thru a cycle of feeding and peaking once in a while helps to check on starter health.  

Now, to save it, take the oldest starter you have and let it warm up and mature (may take up to 24 hrs if very weak) then reduce and use a low feeding portion, like equal weights of starter to flour to see how long it peaks. (not double)  

There is only one thing that bothers me, and that is when you wrote that the starter "seemed to thin out..." which might describe something else or it could mean that the flour and water was separating from lack of bugs & activity to keep everything all mixed up.  How does the starter smell and taste in this weak condition?


proth5's picture

My starter "thins out" when it has not been fed enough or too long has elapsed between feedings or it has been left in too warm an environment.  I am usually able to catch that quickly and fix it.  Since I don't refrigerate my starter it is quite apparent, quite quickly.

We all know that whole grains promote faster activity in yeast.  If you kept to your same feeding routine while adding the whole grains (and rye brings a lot of wild yeasts to the party) I wonder if it just gradually weakened from lack of food while refrigerated. Did you notice anything unusual between feedings?

Speculation only...

flournwater's picture

My theory is that the rye flour, which in my experience is consumed by the yeast more quickly than wheat flour, lost its food valule and the yeast slowly lost its source of nourishment.  If I remember correctly, rye flour starter requires feeding about every 36 hours.  So I suspect you may have starved your starter.

Doc.Dough's picture

I suspect Mini is right (as she usually is).  It can take a long time for dilution to become obvious if feeding is always done a little too early. And the consistency of the process in this case might never have had the occasional "forgot to feed" phenomenon which might have compensated. 

Mini Oven's picture
Mini Oven

actually.  Looks like dormancy from lack of food.  

Pioneer Foodie's picture
Pioneer Foodie

MC Farine wrote about something similar to your experience: that a change in flours seemed to have killed her levain when she was working with Gerard Rubaud. In that case they traced the culprit back to flour which hadn't been properly aged  before using. Apparently it has to season for a month after milling before it is ready to use.

Debra Wink's picture
Debra Wink

Hi SF,

These are the important points that jump out at me: 100% hydration sourdough starter, transitioned from 100% white flour to 50% whole grain. Except for the change in flour composition, nothing else was changed [temperature, refreshment rate, ripening time?]. After initially working okay, the starter became less active (taking longer to double), then seemed to thin out, Finally, it refused to rise at all.

It's not much of a mystery, really, because whole grain is a whole different animal:

  • Firstly, it has a much higher ash content, meaning higher buffering capacity. Higher buffering translates into more bacterial growth and acid production, because the flour can absorb more acid before the pH falls to an intolerable level.
  • Secondly, whole grain provides more co-substrates the bacteria can use to make acetic acid---which yeast are sensitive to. So, more buffering and co-substrates mean more LAB and their acetic acid. When LAB grow with abandon like that, it has a depressing effect on the yeast population.
  • Thirdly, your observation that it thinned out, indicates that things have gotten so acidic from the bacterial activity that the gluten has been degraded by proteolytic enzymes (also greater in whole grain) which are activated by low pH.

It is not surprising that the yeast have checked out if you switched to whole grain, but have changed nothing else. If you want to continue maintaining your starter with whole grain, you'll need to compensate by adjusting one of the other four factors---temperature, hydration, feeding rate and/or frequency. Try firming it up, and feeding more frequently while at room temperature. With whole grain you need to be extra vigilant, so as not to let it remain in a chronically over-ripe condition. Once you get the LAB reined in, the yeast population should come back.

Good luck and best wishes,

subfuscpersona's picture

that - over time - the yeasts got starved for food (primarily due to the whole grain flour, especially the rye). It took awhile for this to become evident.

FYI, the starter wasn't used to raise bread over the summer transition period. It's too hot to bake much in the summer (no air conditioning) so I used the excess for stove top chapati and english muffins. As I said, in the fall I began to use the "new" starter for bread baking in the oven. Towards the end, I did notice a more alcoholic smell to the starter when it was fed. Should have paid more attention instead of persisting in feeding it only once a week with 50% white/50% whole grain flour.

Eventually I want to return to a weekly feeding schedule but I'm going to scale back the % of whole grain drastically. I'll try to revive the starter with 90% white (unbleached) bread flour and 10% organic rye flour. Will probably initially start with a hydration of 125% and, if it shows signs of reviving, gradually scale back to 100% hydration once the starter is established. I'll also feed it initially twice a day (discarding excess). If it doesn't revive by a week with this routine, I'll just begin a new starter from scratch.

Special thanks to Pioneer Foodie for reminding me of Farine's blog posting

MC Farine wrote about something similar to your experience: that a change in flours seemed to have killed her levain when she was working with Gerard Rubaud. In that case they traced the culprit back to flour which hadn't been properly aged  before using.
. (BTW, the direct link to that article is )

I blush to admit that there was one thing that changed in September (when I began using the starter for bread baking). It was the whole wheat flour. Specifically, it was the whole wheat flour used to feed the starter. I milled a new supply of whole wheat flour in the beginning of September. I mill enough flour for several bakings and what isn't used immediately is aged for 3 weeks (in a paper bag in the refrigerator) before I use it in bread baking. However, I was using this (not completely aged) whole wheat flour as food for the starter. My bad! I had forgotten about this when I said "nothing changed".

So... THANKS TO ALL OF YOU! I've learned a number of things - albeit the hard way. I am very grateful to all who took the time reply.

MangoChutney's picture

I never age my milled flour and it doesn't kill my 100% whole grain starter.  I don't believe ageing has anything to do with the suitability of flour as food for yeast.

proth5's picture

I was a bit surprized that non aged whole grain flour was called out the culprit - since earlier installments made a big deal out of how he fresh grinds grains (by hand) to feed the levain. But I couldn't find the source.

Turns out the culprit was green All Purpose flour.

Big difference.  There are just a lot of things going on in whole grain flour that we would consider unaceptable in white flour.  There's some disagreement about the need to age or how to age whole grain flours.  There is none with white flour - that stuff needs aging...

subfuscpersona's picture

I agree. I see no reason why semi-aged home milled whole grain flour would be unsuitable as a food for a sourdough culture, so I would be interested in people's thoughts on this.

I had forgotten that I was using "semi-aged" home milled flour to feed my problematic starter so I just wanted to be accurate and complete in my follow-up post.

My problem was correctly identified as starving my sourdough culture by not adjusting my feeding schedule (or other factors) after transitioning it to a white bread flour & whole grain flour mix. Given all the excellent advice, I was able to revive my starter.

On the other hand, since sourdough starters are so variable among home bakers, I tend to look for clues where I can find them - especially when it comes from a reputable and established bread blogger and is based on her experience with a master baker. Rubaud's starter is quite different from mine, but they diagnosed that the failure of the starter was due to the combination of commercial unbleached white flour that had been milled 9 days prior to use (insufficiently aged) plus a fermentation time for the starter greater than 4 hours.

This is yet another wrinkle for home millers to be aware of. My impression is that most home millers on TFL bake with the flour they mill within 24 hours of milling (and experience no problems). However, a few of us do mill extra flour for future bakings  (and I am one of them). So the debate on whether home milled flour needs to be aged if not used within 24 hours of milling (even if just used to feed a levain) continues.

Farine's post reminded me of the importance of the milling date for my home milled wheat flours. Yikes! yet another thing to remember. Baking with home milled flour is certainly an adventure.

OldWoodenSpoon's picture

to the question of aging home milled flour on starter performance:  I mill my own whole wheat flour.  I feed my sourdough starter on a mix of 95% home-milled whole wheat and 5% BRM Dark Rye flour.  I buy 10 lbs of white whole wheat berries at a time from my local health food store about three times a year, and mill about 2.5 lbs at a time.  I pre-mix my starter feedstock in 500 gm lots from this flour as needed at whatever age it may be, from newly milled to as much as three months old, and all stages in between.  I have not detected any impact on the robust nature of my starter, regardless of the age of the feedstock.  Room temperature, and timing relative to maturity of the starter, tend to be the factors that have most to do with the performance of the starter, both in the jar and in the dough.

For what it's worth

proth5's picture

in advance and with whole grain or nearly whole grain flours, I've use the flour with success with it "aged" as little as a week (or freshly ground).

I don't feed my starter fresh milled flours - it is kept on white flour only. But I speculate that no aging of whole grain flour is required to feed a starter based on the reports that Rubaud feeds his starter freshly ground grain.

When I ask about these things with bakers and millers who should know, I get vague answers like - "aging is OK" or "there is no specific threshold".

If I could, I would use only freshly ground flour because of the taste. 

All of this stuff convinces me that whole grain flours are in many ways different than their white counterparts.

Hope this helps.


subfuscpersona's picture

As pointed out by all, a flour mix of 50% commercial white (unbleached) bread flour, 40% organic whole wheat flour and 10% organic rye flour for a 100% hydration starter is too much food for a 100% hydration starter that is fed only once a week and refrigerated between feedings.

I decided to try to rescue my "failed" starter and am happy to report that it seems to have made a healthy recovery. I have now fed it 4 times, each time with 50 gm starter, 125 gram water and 125 gram flour mix (90% commercial unbleached bread flour + 10% organic rye flour). Feeding schedule was every 12 hours and rising temperature was in the mid to high 70s F. All but 50 gm of the refreshed starter was discarded before being fed again. My starter now looks and smells fine and is peaking after about 7-8 hours. I plan to use it for a baking in a day or two, refreshing it with the same ratio of starter:water:flour mix.

I have one remaining QUESTION for my fellow TFL members. I would like to use a small amount of whole grain flour in my levain. I'm thinking of using a mix of 90% bread flour and 10% whole wheat flour (rather than rye) to feed the levain. (I'm afraid that even 10% rye would be too rich for my yeastie beasties.) Would this work given my once-a-week feeding schedule??

Yet again - thanks! - SF


PS - Was re-reading Farine's blog posts on master baker Gerard Rubaud and found this quote in her blog post at

A baker who normally feeds his or her levain a percentage of whole grains must put it on an all-white diet before storing it in the fridge or it might ferment too much and develop unwanted acids

Just thought I'd include the above quote. BTW, Farine devoted quite a few blog posts about Gerard Rubaud's methods. If anyone is interested in them (they're definitely worth a careful read) this blog post of hers - - gives links to all her other posts about him. They're very detailed and include beautiful photos as well as a number of short videos.


pmccool's picture

my starter has been doing well lately with weekly feedings of Eagle Mills AP which contains 30% white whole wheat.  I do keep mine stored as a very stiff dough in the refrigerator between feedings/uses, so that also works to keep it from burning through its food supply too quickly.  At the refrigerator's temperature of 35F, it takes the starter about a week to peak.


MangoChutney's picture

I am at this very moment eating a lovely slice of my 100% whole grain sourdough sandwich bread, which is nicely risen and not at all brick-like.  The starter is kept at 35F in the refrigerator between episodes of baking, which occur approximately every 5 days.  It is allowed to warm up for about 12 hours before use, then fed and left for another 12 hours before a portion is stored back in the refrigerator for next time.  The starter is fed on 1/6 whole rye, 5/6 whole wheat, and zero refined flour.  It is kept at about 70% hydration.  It is a docile culture, yet productive when needed, with a slight tang in flavor but an aroma principally of yeast.

Mini Oven's picture
Mini Oven

I wait for signs of life.  Wait for signs that the starter is eating on the food and showing it in some rise or slight change in smell before popping into the fridge and cooling it down.  I want it to be able to keep growing and defend itself.  Granted, I give mine a higher ratio of flour to starter than you have stated above (this is the main concern, more so than the type of flour or mixture) for ratio varies with temperature of room, water and flour.  But it might also be interesting that I have also fed my starter non-gluten flours,  bread slices and sometimes fruit or vegetables, anything to keep it going in a pinch.   I think in heat, I might just add a few salty potato chips too!   Just don't expect every type of food or flour to behave in the same manner with the culture.  Some hold gasses (an obvious sign of activity) other may release it but there should be some kind of activity and change going on when the beasties metabolize the food you give them and give off waste products.  

The wee little beasties are pretty good at breaking starches down and taking the needed energy.  If not; when the environment indicates to them that the food supply is low, dry or too cold; they slow down their activity and go dormant.  Dormant yeast lie in wait for environmental conditions to change.   That's what they do in nature and that is what they do in the refrigerator or on the counter top.  All at different speeds and variations of activity.  Slowed beasties wake up much faster after a feed than dormant ones which can take days.  (That is why when waking dormant or dead looking ripe starters, they are fed small amounts to just double their size and the first discard/reduction is after two or three days at 23+°C.)   

If you change feed flours, take a good whiff (or taste) of the wet flour mixture so you are familiar with it and know that it will change (not by much) when adding the starter culture.   If after hours of standing, the starter still smells or tastes bland like when you first fed it,  fermentation is slow and it needs more time or warmth to ferment more before chilling.  If the fermentation is taking too long, then it is time to reduce the food amount or increase the starter  amount when feeding the starter.    A reminder: Fermentation is slow to start and speeds up rapidly as yeast numbers double with each generation.    

I find the problem with diluting the starter with too much food is that when the starter has a difficult time maintaining its defensive balance, it can easily be overtaken by other types of yeast and bacteria, not to mention fungi and other starch loving microorganisms.  This can change the outcome of your bread good or bad and it may never be the "same as before."  The profile can change.  That is when a back up starter is very handy.   When you get this new starter working for you and your schedule, make a back up starter.   Even if it goes ignored and dormant in the back of the fridge, it is better than no backup at all.  :)  

Pioneer Foodie's picture
Pioneer Foodie

I am reminded of Ray Bradbury's Fahrenheit 451, particularly the part when Montag's wife Millie has overdosed, and a team of blood technicians come to filter her back to life. Montag is astounded and appalled that the tech's know nothing about the structure of blood cells or the function of the liver and kidneys; they just know how to plug a person into their machine.

I like Pat's comment that millers and bakers seem to remark vaguely, "there's a range of acceptable procedures." It calls out the art and finesse of baking, rather than boiling everything down to the narrow margins of a technical manual that one should follow explicitly.