The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Sourdough Experiments

davidg618's picture

Sourdough Experiments


I've been trying a couple of things: increasing sourness (based on what I've learned from Debra Wink, and other online references, varying hydration; and feeding portions of my favorite starter different flours, and developing it at different temperatures (part of the sourness investigation.). I've been doing these things one step at a time, so the results don't get clouded.

For the sourness experiments, along with Ms. Wink's super TFL postings, my other main source of information is:

"Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri in Response to Process Parameters of Sourdough Fermantation"; Michael G. Ganzle, et al; Applied and Environmental Microbiology, July 1998


an answer provided by the above author to the question, "What is the relationship between temperature and activity?" in a Q and A blog relating to sourdough.

Sourness: flour and temperature

First, an apology, and a plea. Although I am educated as an engineer and scientist, microbiology is far distant from my underwater acoustics speciality. I've struggled, mostly with the  subject-specific techincal language, in my effort to understand what I've read. Nonetheless, I think I've acquired the background of  knowledge that a home baker, obsessed with sourdough, can use in his or her non-laboratory kitchen to effect the flavor profile of their sourdough breads. Please, if you find my efforts have been based on faulty premises, wrong information, or misdirected experimentation point out the errors, and, more importantly the correct assumptions; accurate, alternative references; or suggest appropriate action--including, "Stop your silly mucking around!"

Debra Wink, in one of her postings, commented that that a flour's ash content contributed to the degree of sourness one might achieve in a starter, but didn't explan how. The first of the above references shows that the activity (reproduction) of Lactobacillus is strongly linked to the the starter's pH ( a measure of acidity). As the acidity increases. or decreases, above or below a most  activity-advantageous value (approximately a pH of 4.2) L. Bacillus reproduction decreases. Assuming, for the moment, the temperature of the starter remains steady, and the activity-advantageous pH can be preserved, the amounts of acetic and lactic acid produced is proportional to the concentration of L. sanfranciscensis. However, in any solution the more acid the lower the pH. Some molecular components of the starter's mix may neutralize a portion of the acidity, while maintaning its sourness contribution. In flour and water mixtures that neutralizing (buffering) quality is supplied by the flour's ash content. Simplistically, I thought, the higher the ash content in the feed, the greater the buffering quality of the flour, and, therefore, the more acids produced before the bacteria activity slows down.

With that in mind, I fed a portion of my favorite starter, at room temperature, for three days a steady, every-twelve-hours diet of first clear flour, known to have high ash content. This became my seed starter for three formula-ready levains. In general, this starter, aledged by the vendor to be authentic San Francisco sourdough starter, doesn't produce much discernable sourness, if any at all. On a few occasions, we (my wife and I) have detected some sourness, which has allowed me to conclude there's some L. bacillus in there, maybe.

After 72 hours I built 500g of formula-ready levain,at 100% hydration, using first clear flour; it contributed 28% of the total flour weight. The balance of the dough's flour consisted of 10% rye flour, 31% all purpose flour, and 31% bread flour. The final dough contained 2% salt, at 70% hydration. This formula was used three times; each bake consisted of two loaves, formed into approximately 750 g batards. Every loaf was processed as indentically as possible in a home kitchen: two and one-quarter hour bulk proof with two S&F at 45 minute intervals, followed by an additional 45 minutes. Subsequently, the dough was divided, preshaped. rested for 10 minutes, shaped, final proofed for two hours, slashed and baked at 450*F, with steam for the first 15 minutes. The remaining seed starter was stored in the refrigerator at 37°F.

The only intentional variable was in the levain constructions.

First levain: 20g seed starter, three 1:1:1 feedings of first clear flour, initially and at eight hour intervals. Harvested 500g of levain after 24 hours. The developing levain remained at room temperature (68°F to 72°F) for the entire duration.

Second levain: 20g seed starter, three 1:1:1 feedings of all purpose flour, initially and at eight hour intervals. Harvested 500g of levain after 24 hours. The developing levain remained at room temperature (68°F to 72°F) for the entire duration.

Third levain: 20g seed starter, three 1:1:1 feedings of first clear flour, initially and at eight hour intervals. Harvested 500g of levain after 24 hours. This levain was held at room temperature for the first eight hours, approximately 82°F for three hours, and 89°F for the remaining 13 hours. These temperature choices reflect the findings reported in the first reference: optimum yeast activity occurs at approximately 82°F; optimum bacteria activity occurs at approximately 89°F. Additionally, yeast and bacteria activity are approximately the same at room temperatures, yeast activity falls dramatically at 89°F.

Subjective Results:

First of all, these were not meant to be controlled, scientific experiments. To the contrary, what i wanted to explore was, "Can a home baker influence the flavor profile of his or her doughs, guided by scientific results, with only those tools common to a baker's home kitchen?".  In my case, a small, lidded plastic box,for the developing levain; placed inside a larger, lidded plastic box (my dough proofing box) to minimize the effects of drafts; all placed inside an oven with a manually controlled oven light, to vary the oven's temperature); and a thermometer, aledged by the manufacturer to be accurate to +/- 1°F).

Furthermore, the only way I could test a finished bread's sourness was by tasting it. (in the laboratory they measured the amount of lactic and acetic acid produced.). My taste would be suspect: I was hoping for discernable sourness with the first and third levains; I would taste discernable sournesss with the first and third levains. So, I asked my wife to taste the finished breads. She had no knowledge of the differences in the levain, nor what my expectations were.

The results are a bit anticlimactic:

We both found breads made with the first and third levains had discernable "tang"; in part because we didn't taste them side-by-side, niether she nor I could state with any certainty one was "tangier" than the other.

The bread made with the second levain, fed with all purpose flour, didn't have any "tang". Good bread, but no sourness.

Next steps:

I'm building a proofing box, wherein I can control temperature better than with the oven light. When its finished, I'm going to push a levain to favor only bactieria growth, and add commercial yeast to the dough for gas production.

Here's a picture of the most recent (third levain) bread.



pmccool's picture

My own thoroughly non-scientific empirical observations suggest that whole wheat flour will produce a finished bread with a much more sour flavor than the same bread made with white flour.  Some have been too sour for my tastes.  I have no clue about the microbiology or biochemical processes at work, since I haven't the necessary skills or equipment to analyze whatever is going on.  All I can say with any confidence is that a whole-wheat sourdough bread (my kitchen, my ingredients, my processes) is more likely to have a stronger sour flavor than will a white sourdough bread, all other things being equal.

That's probably no help in what you are trying to achieve but it is something that I have observed.


davidg618's picture

Thank you. I'm not trying to do anything scientific, but I am trying to understand directions I can go, and directions not to go. All my life I've turned to books, or learned papers for accurate information, but that's just my training. As I said in my post, I want to know what I might be able to do in my kitchen, not a laboratory. However, I'll glean that info from any source I think I can trust. I've read a lot of your posting; you're on my trustworthy list.

I switched from adding whole-wheat to my sourdoughs about four months ago to adding rye flour, long before I reached this level of enquiry in my doughs--I've only been making sourdoughs for about eight months. The switch was flavor driven. My first goal in baking and cooking is flavor. Do you have any comment/experience with rye flour? Do you have any best-guess--despite your claim of ignorance in your post--why the whole wheat breads are more sour?

David G

pmccool's picture

but it probably has something to do with the higher ash content in the whole-grain flour, per the same literature that you have been reading.  There may also be something that is unique to the chemical content of whole wheat itself which provides the micro-organisms in sourdough with a different feedstock (thinking in petrochemical terms, now) and yields a different slate of products.  That is purely speculative, though, and I have no means for analysis that would prove or disprove that notion.

Rye flour and sourdough make a very happy marriage.  One could almost say that rye bread just isn't rye bread without sourdough.  Conversely, the addition of rye flour in relatively small amounts, usually less than 10%, brings new layers of flavor to an otherwise "white" bread, even though it doesn't taste like a rye bread.  Many country-style loaves, such as pain de compagne, include small percentages of both rye and whole wheat flours because of the additional flavors they bring to the party.

For a real education in rye breads and the use of rye flour, I would point you to ehanner, hansjoakim, dmsnyder and minioven.  There are other posters whose names elude me at the moment that also work extensively with rye, but reading those four posters' work will give you a very good foundation for utilizing rye flour effectively.  And you'll find commentary by others that will lead you to the posters whose names I'm not recalling at this instant.  If you can borrow a copy of Greenstein's Secrets of a Jewish Baker, you'll get a lot of great rye bread formulas from a master baker, though not so much of the science behind them.

Hope that helps.


davidg618's picture


Thanks for the well thought out response. I've dabbled with rye breads (Hamelman's 40% rye, vollkornbrot, and a weekly sourdough that contains 30%) but, except for the sourdough I haven't explored rye breads properly. It's been on my list to do so, but I can't seem to get away from sourdough. Each success or failure leads to more questions or ideas, but eventually, I will delve into rye breads with equal fervor.

I read all those posters you suggested, daily, and I visit Breadtopia, and search the web in general frequently. I've not neglected other around-the-house-projects, but bread baking has become an obsession. I don't think I've been this focused since I retired more than a decade ago.

David G

Faith in Virginia's picture
Faith in Virginia

Hello David,

I just made a 100% whole wheat using a culture from Sourdough International (New Zealand for rye)talk about sourdough...this bread almost makes you want to pucker. Cream cheese makes it worse. I like good sourdough but this was over the top for me. Now I'm working on cutting it back so I'll reduce the amount of whole wheat and cut in some bread flour.

That is some nice looking bread and keep us posted on your trials. I would like to make the Italian culture more predominant in my white breads. I'm still learning so I read all this with great interest.

Thanks Faith

rockfish42's picture

Sounds like the next step would be attempting a firmer levain and or retarding the loaves overnight. I live in SF and normally bake the Vermont Sourdough from Hammelman, this bread has 10% rye and with an overnight retard gets a good level of sour. I'm still looking for a recipe that will give me something more closely approximating a proper SF sourdough, something that would've been labeled a dark bake extra sour 20 years ago.