The Fresh Loaf

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SFSD - Lactic or Acetic?

BobbyFourFingers's picture

SFSD - Lactic or Acetic?

This got buried in a thread so surfacing if here: 

Is true San Francisco sourdough more acetic or more lactic?

Additionally, how extreme is the sourness of true San Francisco Sourdough? Pucker inducing sourness or mild enough that you can taste the grain?

idaveindy's picture

1.  From page 23 (Kindle edition) of "The Sourdough School" by Vanessa Kimbell:  (underlining mine)

"In one of the earliest studies of the leavening action of sourdough by two researchers, Sugihara and Kline, conducted in the early 1970s, the principal yeast they found was Candida milleri (now known as Candida humilis) and the dominant lactic acid bacteria was Lactobacillus sanfranciscensis (a heterofermentative Lactobacillus species meaning that it produces more acetic acid).

Unusually for yeast, Candida milleri likes to eat glucose and fructose, and is more tolerant of the predominantly acetic organic acids that Lactobacillus sanfranciscensis produces. C. milleri also doesn’t digest maltose, which the L. sanfranciscensis loves. This is a great example of how the microbe’s choice of ‘food’ affects the kind of bacteria that it hangs out with and it explains why San Francisco sourdough is more sour.

In simple terms, the L. sanfranciscensis has more ‘food’ and so it produces more acetic acid, therefore the resulting bread is more sour. This is just one example of one starter –we are just beginning to understand these relationships and we are learning that each sourdough starter culture has its own combination of individual microbes, and each colony is unique to its environment. There are many different combinations of bacteria and yeasts, all producing slightly different flavours, which become even more diverse when bakers start getting creative with their flour. Although there are sometimes several different kinds of yeast and bacteria in a starter, usually there is one dominant yeast and several more species of LAB."


2.   No, not pucker inducing sour; you still very much taste the bread. But true SF sourdough is more sour than many other types of sourdough cultures that do not have the Lactobacillus sanfranciscensis.

I am currently using "Carl's" Oregon Trail sourdough starter, and it is noticeably milder, less sour, than the previous culture I used from Cultures For Health.  I think I was using CFH's "Desem" or "Whole Wheat" starter culture.  I miss the "tang" and I plan on switching back.   Unfortunately, I killed off my previous starter by freezing it too long instead of just dehyrdrating it.


BobbyFourFingers's picture

Great information. It never occurred to me that acetic acid could be a metabolite of Lactobacillus sp. I assumed some other bacteria was responsible for the acetic acid.

Thank you for describing the sourness of SFSD. The bread that prompted this question was so sour that I couldn’t taste the famously flavorful landrace grain they used and it was over all unpleasant to eat. It prompted me to ask this question because it was a genuinely unpleasant tasting bread, such that I couldn’t imagine it becoming world renowned.

Other issues with the bread suggested to me that their dough was having problems from proteolysis: flat batard, strangely dry crumb, etc.

Confirming that SFSD is not supposed to be as sour as a vinegar potato chip helps confirm that the problem is with proteolysis and that this sourness is not true to type.


idaveindy's picture

It is possible to let sourdough starter get too acidic if you don't refresh it enough, or if you don't discard/use it up as you go, or feed it at too low of a ratio. Also, it's possible to ferment mixed dough  too long and sort of turn  the whole dough mass into starter.  So it sounds like the sample you tried had some kind of problem.

BobbyFourFingers's picture

They are a professional but relatively small bakery. I got a sample of their starter and found it was weak compared to my rye starters. It double once in 24 hours, my rye starter #1 tripled twice in the same period. Both were temperature controlled and fed 1:5:5 by weight. 

I think you are spot on about them letting the dough ferment too long. My guess is that they are trying to make an exceptionally sour sourdough but it gets enzymatic problems after such a long fermentation. The peculiar dry texture is less like stale crumb and more like the gels that make bread soft have been stripped out. It’s really odd.

Of course I wish them well. I was merely curious if their SFSD, which is their shtick, should taste (and have problems) like it does.

After the comments here and the other thread, I think I have an almost complete answer.


Flavor Chemist's picture
Flavor Chemist

In fact, some of the breads labeled San Francisco *sourdough* are not authentic sourdough at all, but commercially yeasted bread made sour by the addition of vinegar. 

Some San Francisco bakeries have long added vinegar to make their bread more sour.
That's not such a bad thing -- after all, vinegar is what the heterofermentative lactobacillus pumps out anyway. Adding vinegar is merely a shortcut. What's produced is a specific style of non-artisan, very sour bread that's called San Francisco "sourdough" but it's really not. 

Sour bread bakers can legally add vinegar to make their bread more sour, if they do not wish to coax the lactobacilli into pumping out more acetic acid (artisan baking). 

They can do that, and not disclose the vinegar addition on the label, because the FDA allows large exceptions for what is called a sub-ingredient, a “substance...that is present in a food by reason of having been incorporated into the food as an ingredient of another food, in which the substance did have a functional or technical effect.”

The rule that allows that is from the FDA Code of Federal Regulations — and the specific passage on sub-ingredients is from CFR 101.100(3) i.

All this goes back to the fact that many breads marketed as “sourdough” actually are sour breads — and there’s a big difference between the two. 

 “Most commercial sourdoughs aren't actually sourdough breads. They are yeasted breads that have had acetic acid, malic acid, and/or fumaric acid added to them.”


There a few tips that indicate a "sourdough" isn't authentic and is really a sour bread.
Sour breads made with vinegar lack the complexity of true sourdough. They lack lactic acid, the other definitive acid in sourdough, and the mellow flavors and aromatics of creamed corn, a dairy-ness or cheese quality, and a discernible sweetness.

Authentic sourdoughs, even those with lots of LAB-produced acetic acid, are never as pungently sour as "SF sour breads." They're more mellow because of the lactic acid. 

The second tipoff is texture: Sour breads are dense, with a fine consistent crumb.
Authentic sourdoughs have a loose, open crumb.

So there’s a distinct possibility that what is perceived as extra-sour "sourdough" is actually a sour bread and not sourdough. What is remembered as being old-school authentic may not be.

The reason for the deception in labeling is because there are such huge profits and tourism dollars in marketing bread as “San Francisco Sourdough.” 

I’m sorry to dispel this myth, because the story of discovering the mysterious microbiology of SF sourdough is truly wonderful. It's upsetting that some bread marketed as “San Francisco Sourdough” isn’t made from a sourdough starter at all and is instead a commercially yeasted, sour bread made with vinegar to fake a sourdough flavor.

BaniJP's picture

I believe the original SFSD was just a regular yeasted bread with acetic acid added to it. No sourdough, just artificially soured/flavored. But from that emerged this whole sourdough baking culture.
It's just mildly sour, as it's often used as a side with other dishes.

That's what I heard in a documentary, anyone from SF can confirm?

mwilson's picture

What is that exactly? Did the Californian gold rush miners not make their own bread before the production of commercial yeast?

I presume you believe the moon landings were faked because you saw it in a documentary...

Since you suggest only those that live in SF can confirm this, as a UK resident you can disregard my comments...

BaniJP's picture

As I said, it's just something I heard in a documentary, but I can't confirm or deny it. I don't know whether it's true, I'm no expert in baking history. I just found it somewhat plausible, given the amount of additives we often have in breads. That's why I asked for help, I'm happy to be proven wrong.

mwilson's picture

Really there is no "True" San Francisco sourdough only echos of the tradition and reputation.

The common belief is that SFSD is reputable for its sourness. I remember seeing a paper that described the ratios of various breads from big producers and while they varied, the typical ratio was closer to the 2:1 range. (lactic:acetic).

This range is atypical. Most sourdoughs fall in the 3:1 - 4:1 range i.e. more lactic.

But what really makes sourness is the total acid (Often measured as TTA (Total Titratable Acid) in the world of bread) and SFSD is noted for elevated levels.

BobbyFourFingers's picture

The ratios are informative, but as you say the TTA is going to be more telling. I like acetic acid (enough that I practically drink some traditionally brewed Japanese vinegars) but the SFSD bread I had was unpleasantly sour for a bread.

Do you think that the sourness of a so called real San Francisco sourdough would put it at about the same sourness as a salt and vinegar potato chip? That’s about how this bread was.

mwilson's picture

It was here TFL member Chris, a passionate advocate of old-school SFSD posted to a paper examining the specs of various SFSD bakes.

dmsnyder's picture

Well, from what I remember ... back in 1849 ...

Truthfully, my memory of San Francisco Sourdough only goes back to the 1950's. And I would argue that the 1950's to the mid-1970's was the golden age of SF Sourdough, or at least the era during which its reputation grew. And note that that is not to say "golden age" implies that the SF SD breads of that time were better than before or after.

Anyway, during that period, all of the SD breads in SF were not exactly the same, but, in general, they were acetic-acid forward. My personal favorite was the bread from Parisian Bakery which, while assertively sour, was well-balanced. In contrast, I find today's Boudin breads offensively sour. The closest to the old-style SF SD is the special bread Boudin bakes exclusively for the Tadish Grill restaurant on California Street.

The very excellent SF SD's being baked today by Acme, Tartine, SemiFreddi, et al. are generally less sour and more similar to French-style pain au levain. And the breads baked by Ken's Artisan Bakery in Portland, OR are as good or better than any of these, IMHO.

Among those in my generation who grew up on SF SD, one will find strong preferences for one or another of the old bakeries breads. That's okay and not be disputed.

I still miss Parisian Bakery sourdough, AKA "Wharf Bread."


BobbyFourFingers's picture

I think “offensively sour” is a great description for the local SFSD bread I had. Do you think that the offensively sour bread from Boudin is inaccurate to the SFSD you tasted during the “golden age”?

It’s fascinating that things have changed so much that they are nearly (or entirely?) lost to time. It’s marvelous that you have tasted them during this period and have taste memory.

DanAyo's picture

David, I really value your opinions! Especially when it comes to SFSD. Being a life long resident of Louisiana, and having never tasted the real SFSD puts me at a huge disadvantage when attempting to duplicate the famous bread.  After years of searching, I settled on a sour that I like best. I love the smooth lactic acid flavor.

I was surprised when you wrote that the SFSD of the 1950-70 favored acetic acid. Although refrigeration was available then, the process I read about never mentioned retardation. One process, that I know you are familiar with, mentions proofing at 105F.

Am I correct to assume that acetic acid favors cold temps and lactic, warm temps?

We can no longer purchase the real deal. I believe a starter will change flavor profiles over time, unless strict maintenance (environment, temps, feed) is keep identical. MAYBE Puratos can maintain a starter as the original, but I’m not even sure about that. What are your opinions about this paragraph? I am interested to know.

We are very fortunate to have bakers that actually tasted the bread when it was in it’s glory. Thanks for speaking up!


dmsnyder's picture

Well, the "science" says acetic acid favors low hydration and cold temperatures. Yet the published procedures for SF SD have high fermentation temperature. The dough hydration is low.

There are at least two more variables: The proportion of starter in the final dough and the fermentation time. The sourest bread I have made was from a formula by the SFBI for a very traditional French sourdough. I think it was the method used in French villages for hundreds of years when each household mixed their own dough but took it once a week or so to the village baker, who had the only oven in town. The method built up the dough with daily feedings for most of a week. The pre-fermented flour was the majority in the dough. It was an interesting experiment, but not worthy of repeating. Much too sour to my taste.

I am an online friend of the son and grandson of former owners of Boudin and Parisian (and other) Bay Area sourdough bakeries. He bakes at home now. His method is to use a 60% hydration starter which he keeps in the fridge and feeds infrequently. His dough uses 25% starter and 60% total dough hydration. It is 100% white flour. He cold retards for over 24 hours. I suspect his bread pretty well replicates the "classic" SF SD. 

I have used Ed Wood's SF starter years ago. It made bread with the real SFSD flavor for a few weeks. Gradually, as you suggest, the flavor changed. But then I didn't maintain it exactly as Dr. Wood prescribed.


idaveindy's picture

Ed Wood, researcher, author, and manufacturer/seller of 15 different SD cultures, writing at:

"In 1997 we acquired the authentic San Francisco culture with the wild yeast now classified as Candida humilis and with the bacteria classified as Lactobacillus sanfrancisco. We guarantee this culture contains these organisms as the dominate organisms of the culture. The two organisms have a symbiotic relationship that has helped them survive for over a century."


Just checked "The Bread builders", page 48 and 49, and the authors mention the same yeast/LAB combo as above.  More details about biology of fermentation on pages 52-56.  TBB also cites Sugihara and Kline. 



Flavor Chemist's picture
Flavor Chemist

For a long time, they were thought to be the same, but it appears the two have now been differentiated in The Yeasts (fifth edition) in September 2016. 

There is still some debate about this. Here are the references:

Candida humilis (= Candida milleri)Kurtzman and Fell commented on the synonymy of Candida humilis and C. milleri in The Yeasts: a taxonomic study (1998). These comments were based on the fact that these two species have identical sequences in a 600-nucleotide region of the LSU rDNA (Kurtzman & Robnett, unpublished data).
 Candida humilis (=/= Candida milleri)Based on The Yeasts (Fifth Edition), Candida humilis and Candida milleri were resegrated on September 19 2016.


Jacques et al. (2016)Jacques N. et al. 2016. Three novel ascomycetous yeast species of the Kazachstania clade, Kazachstania saulgeensis sp. nov., Kazachstania serrabonitensis sp. nov. and Kazachstania australis sp. nov. Reassignment of Candida humilis to Kazachstania humilis f.a. comb. nov. and Candida pseudohumilis to Kazachstania pseudohumilis f.a. comb. nov. Int. J. Syst. Evol. Microbiol., 66:5192-5200.
doughooker's picture

<<  The closest to the old-style SF SD is the special bread Boudin bakes exclusively for the Tadich Grill restaurant on California Street.  >>

I strongly disagree. I made a special trip to the Tadich Grill for the express purpose of sampling their sour bread. It was a far, far cry from the old-school bread I grew up with in the '60s. Almost totally absent was the distinctive lactic-acid tanginess that's very familiar to me and was characteristic of such breads as Larraburu. The bread was sour, but artificially so. I have a feeling the sourness resulted from the addition of additives, possibly a combination of vinegar and fumaric acids.

Acetic acid is basically vinegar. Proper SFSD does not have a strong vinegar component in its flavor.

I have successfully made the following recipe twice. It was plenty sour the first two times but has not worked for me since and I don't know why. It just tastes a little salty. Maybe it's the flour? I need to try this recipe again with different flour. It uses whey as its source of lactic acid and vinegar as its source of acetic acid. The whey can be obtained by draining plain (unsweetened) yogurt.

As to whether the bread is too sour for your taste, that judgement is best left to the individual. My problem is that my loaves never seem to be sour enough. I grew up with it so I love it.

I now live in southern California and have found a very, very good sourdough at Sprouts market and at Gelson's. It is Old Town Baking Company Miner's Sourdough. Unlike SFSD it is sliced and has a soft crust. The flavor is plenty satisfying.

mwilson: Thank you for the kind remarks.