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question for you experts about wild yeast vs. commercial yeast

flourgirl51's picture

question for you experts about wild yeast vs. commercial yeast

There seems to be some debate regarding the health benefits of wild captured yeast captured using apple or potato peelings vs commercial yeast. Does all wild yeast yield a sourdough type bread? I have heard people make claims stating that commercial yeast is bad for you but they can't back up those claims with any concrete evidence, only their personal opinions.  I would like input on this from anyone that knows the real difference between the two. Thank you.

Yerffej's picture

It is a matter that goes far beyond just the yeast.   Commercial yeast, Saccharomyces Cerevisiae, or "sugar-eating fungus", is used as a matter of convenience and profitability.    That is, a yeast that can be used to crank out lots of bread fast...very fast.   So fast in fact that little complete fermentation takes place and the natural balance of yeast and acid never comes to be.

In the sourdough world an entirely different yeast, the principal yeast being Candida milleri is doing the work.   In addition to yeast, sourdough starter also contains bacteria, predominantly lactic acid bacteria belong to the genus Lactobacillus.

Sourdough benefits include a longer shelf life, better flavor, and healthier bread.  The longer fermentation time of sourdough breaks down proteins into amino acids for a more readily digestible bread.  Sourdough bread is essentially a fermented food and like other fermented foods it is good for your health. Sourdough bread can aid in ensuring that your blood glucose level remains in line, helping to guard against various diseases such as diabetes. This is all in contrast to the use of commercial yeast employed for quick production.

The glycemic impact of sourdough bread is low as compared to commercial yeast.  The inclusion of lactic acids (and acetic acids) makes for a much healthier and more readily digestible product.  Found in grains, naturally occurring phytic acid, which is not good for digestion by a single stomach such as we humans have, is reduced or eliminated in sourdough but remains in commercially yeasted breads.

Your question is large and this answer is brief touching on but a few points regarding the benefits of sourdough. Hopefully I have given you enough for you to further pursue the topic.


p.s. 99% of the breads I bake are sourdough breads.   First for health and secondly for flavor.


Mini Oven's picture
Mini Oven

narrows the discussion too much. (we can also discuss the dangers of potato peels) I would leave these words out of the question.  My sourdough starter was not started in this method.

As I understand it commercial yeast is one type per package (and they can be different strains from one another depending on the company) whereas "wild" are a group of different yeasts with their accompaning bacteria. 

So is the Question:  What are the differences between using natural fermentation and single strain yeast fermentation?  --and--   Where can I find the scientific evidence that there are health benefits in using one over the other?

I feel we have it posted somewhere...  I do remember reading such reports.  I will go diving in the archives...  somewhere...  I do think I will come out covered in sd goo.

Do remember that these types of studies are not normally funded in the USA because no one is making big finantial gain on traditional sourdough.  (Research goes where the money goes.)  That's not an excuse, it just means one has to look all over the planet.  These studies tend get burried in the USA.  Fermentation is very well studied in relationship to food outside the USA.

Mike Avery's picture
Mike Avery

There are few areas with as many unfounded misconceptioons as sourdough.  I call 'em old husbands tales.


Let's start by dismissing apple peelings, potato peelings, grapes, cabbage leaves, yogurt and other odds and ends from the discussion.  The yeasts and microorganisms on them are best suited for fermenting apples, potatoes, grapes, cabbage leaves, or yogurt.  The organisms that are found in the wild and are best suited to fermenting wheat, rye and the other grains we usually eat are already on those grains.  Using other things to "help" the process will get things moving quickly, but you won't have sourdough until the critters from the grapes, cabbage, etc. die off.


Next, if you talk about "sourdough yeast" you are missing half the picture.  Sourdough is a symbiosis between a strain of lactobacillus bacteria and a strain of yeast.  The bacteria makes the culture acidic, so only a few strains of yeast can survive in a sourdough culture.  The strain of yeast used as bakers yeast is not one of them, so if someone talks about starting a sourdough culture with a bit of yeast, smile, nod and keep looking for another sourdough guru.  One cookbook says that a speck of bakers yeast will "attract sourdough yeast".  Yeast don't have much control over their motion or direction.  It's not like a bird flying overhead and seeing worms.  Airborne yeast go where the wond takes them.


The bacteria have a number of defenses against other critters taking over the culture.  The first one is the acidity.  Sourdough cultures are too acid for much to live in, and luckily for us no human pathogens I've heard about can survive very long in a sourdough culture.  The bacteria also produce about 50 antibacterial compounds that have been identified so far.  The lactobacillus really wants to be left alone!  The yeast, as a result, enjoy a pretty cushy life.  Not many organisms to compete against, turning carbs into alcohol and carbon dioxide and multipying.  What do the bacteria get out of the deal that makes it a symbiosis?  Some biologists say that the bacteria eat the dead yeast.  They can also eat some sugars in the grains, and they can at times eat the protein in the grains.  This omniviorous quality means that sourdoughs tend to be a bit slacker than a yeast risen dough with the same hydration.  It also means that if your culture goes rogue, you can have some real issues in your bakery.

One of the interesting things is that there are a number off strains of bacteria and yeast that can form viable sourdough cultures.  And, as often as not, many of them are already on the flour used to start a culture.  Which strains become dominant depends upon, among other things, the thickness of the culture, how often it is fed, what it is fed, and the temperature at which it is kept.  While, in general, one strain of yeast and bacteria become dominant, there are other strains of lactobacilluis bacteria and yeast in natural starters waiting for an opportunity to take over the culture.

Now then, if you just mix flour and water, will you get yeast or a sourdough culture?  Almost always, you get sourdough.  However, there have been a few recorded instances where people had yeast cultures with no bacteria.  In general, if you keep feeding your culture and handling your culture, it will become a sourdough culture.

This post is long enough already.... I'll answer a few more of your questions in the next one.




There has been a recent explosion in sourdough reasearch, which is really neat.  I have about 40 "must read" papers on my computer.  My comments are based on reading the abstracts.

Mylissa20's picture

Ok Mr. Mike Avery, you've got my attention with all your science and wisdom.  Hit me with your resources so I can learn more!  I'm an avid reader, so no list could be too long....  Thanks!

Mini Oven's picture
Mini Oven

Look in

Journal of Cereal Science,  Sourdough Bread: Startch digestability and postpradial glycemic response

Mike Avery's picture
Mike Avery

and on and on and on....

Starting somewhere between 6,500 and 10,000 years ago, depending on which food anthropologist you believe, man started eating leavened bread.  Some feel that a hunger for bread, and beer, were largely responsible for man giving up a nomadic lifestyle and settling down.  It's hard to tend crops when you're a nomad.

And until the mid to late 1800's, most bread was risen with either sourdough or barm (yeast scavenged from fermenting ale).  And no one had ever, as far as I know, heard of gluten intolerance, celiac disease or sprue.  More recent studies show that sourdough breaks down gluten.  And some studies suggest that it may be fine for people with celiac, sprue and gluten intolerance to eat sourdough bread.  (Note - I am not a doctor, and if I were, I still wouldn't be YOUR doctor.  If you have these issues, check with your health care professional before making any changes to your diet.  Unless reincarnation happens, you only get one body, so take care of it, OK?)

In the mid to late 1800's, commercial yeast became available.  And bakers switched in droves from sourdough to yeast.  It was easier to use.  It was more predictable in the hands of inexperienced appreentices.  There was no feeding the starter.  It was the dawning of the age of... miracles?  Atlantis?  the promised land?

There were two little clouds on the horizon.  One was the customers.  The new breads, made with a straight yeast process, just didn't taste good to people who were used to the greater compexity of levain or sourdough.  And the bakers realized they had to pay the yeast company every time they made bread.  NO ONE is as cheap as a baker.  (In the defense of bakers, it has to be said that the margins are really, really tight.)  Luckily, the answer to both questions was the same.  Long slow fermentations using bakers yeast.  Poolish, biga and sponge all take very small amounts of yeast and culture them for hours.  Typically 12 for poolish and 18 for biga.  And then the bread is given a long rise.  How much yeast is in a poolish based bread?  I make about 25 to 30 loaves of bread with as much yeast as is used in a single loaf of typical straight process yeasted bread.  And the rises are also longer.

And celiac, sprue and gluten intolerance were still largely unheard of.  The long ferments bring complex acids to the dough, an increase in flavors, and some denaturing of the glutens.   Not as much as sourdough, but some.  Maybe even a significant amount.

As a side note, when I was running my bakery we did aging tests of sourdough and poolish based breads. Poolish based breads typically lasted about 2 weeks before they molded. Sourdough breads made it about 3 weeks. Straight process yeasted doughs, without preservatives, will make it a few days.

So, what's changed?  Andrew Whitley has some ideas.  Google him and "what's wrong with bread".  My view?  What happened, in a nut shell, is World War II.  And everything changed!

We moved into a new industrial age, and everything changed.  Before WWII, most people engaged in physical labor.  And since then, even though we work less, we eat more.  And that's not just in fast food joints and restaurants - look at suggested serving sizes pre WWII and post WWII in cookbooks - a serving is more than 30% larger today than then, even through people are less physically active.

We have changed how our food is grown.  Wheat yields are as much as twice as high as before WWII.  However, the nutritional content has declined at about the same rate.  What other changes are there in the foods we grow?

How ingredients are processed has also changed.  Pre WWII, white flour was made largely by grinding the grain and bolting the resulting ground flour, or separating the bran from the flour, which is called "straight process flour".  Now, the flour is separated into many components, called streams, which come from different parts of the wheat kernel and have different characterisitics.  The mill recombines a number of the streams to make the bread and all-purpose flours we purchase.  It is hard to know what the signifigance of this is, however, we are eating a very refined flour.  Old style bolted, or straight, flour is far more complete, which is probably a good thing.

Culturing sourdough, poolish or biga seemed too time and labor intensive, manufacturers wanted to make bread faster.  So, flour was treated with chemicals to make better dough that would handle better and rise better.  Yeast was injected at mixing at very high levels.  Fungal amalyses have been introduced that help the bread making process.  Andrew Whitley points out that in England they don't have to be disclosed as ingredients because they are processing aids that bake out of the bread.  However, he points to some studies that suggest the amalyases change the structure of the gluten so it is more of a problem for people that have gluten issues.  From dough mix to bagged and on the delivery truck takes about an hour in some modern bread factories.

Before WWII, people eating a pound or more of bread a day was not uncommon.  Obesity and gluten sensitivity issues, however, were very uncomon.  As a side note, Andrew Whitley points out that cultures which have a tradition of eating wheat that was not fermented a long time have a higher incidence of gluten issues than cultures that eat fermetned wheat products.  The example that comes to mind would be the Irish and Irish Soda Bread.  It is chemically risen, not fermented.  Many people today don't care for the taste of mass-market bread, and complain they have trouble digesting it.  And the bread factories seem to blame the consumer.  "Why aren't they buying and eating our product?"  Interestingly enough, artisanal bakeries aren't having these issues.

My feeling is that when you decry yeast and equate yeast with fast risen bread, you are looking at a very small part of a much larger picture.

It might be informative to unravel some of the changes that have been made.  Try longer rises with yeast using poolish and biga.  Look for straight process flours.  Look for bolted flours.  Look for heritage flours, such as Turkey flour (Heartland Mills sells that on a limited basis).  I've played with Turkey flour and am looking for other heirloom flours.  The results are interesting.

I hope flourgirl15 found some of the answers she was looking for here, and that she'll look at Andrew Whitley's web pages for more information.  In the end, it isn't just the yeast.




Yerffej's picture

Nice informative post.  Thanks Mike for taking the time to write it,


gary.turner's picture

I will echo Mike and habahabanero's comments and add a smidgen. [ot]As much as I love spicy foods, the only use I've found for the habañero is that it can remove the chrome from a bumper hitch. :)[/ot]

Commercial yeasts are derived from brewers' strains, where the requirements are more strict than any wild yeast source can match. The sour produced by bacilli are particularly anathema to the brewer. Brewers will carefully nurture their cultures to produce as pure a strain as possible for each particular beer type. And, it is, after all, brewer's yeast we use as a vitamin supplement.

The natural is good, commercial is bad argument is a straw man. You want natural? Make yourself some oleander tea, or mistake foxglove for comfrey; and die. Try some cold pressed wheat germ oil as a vitamin E supplement. You'll get as much estrogen as E. That may not be a Good Thing. If you are poor, cannot afford meat in your diet, and corn is your staple grain, you may develop the dietary deficiency disease, pellagra. Until recently, it was common in northern Italy and the American south. Why? Because corn needs a chemical treatment to make its Niacin (Nicotinic acid vitamin) biologically available. Treat the corn with potassium hydroxide, lye, and the Niacin can be used. Maybe chemical treatment isn't so bad.

We must look at each case in its own context, and apply our own sanity check to the all too many scare stories that keep popping up.

It's hard right now to accept so-called peer reviewed papers.  So  many seem to have been "reviewed" pretty uncritically. Mann's infamous hockey stick graph that got Gore all orgasmic somehow missed the Minoan, Roman, and Medieval warm periods, and he had to ignore his own proxies for the last 50 years because they diverged from known, measured temperatures. But the proxies were right until then. Right. Peer reviewed. Bifra tried to reproduce Mann et al. and ended up discarding all data except from one tree's rings. Then, the statistical methods he used were found to create the hockey stick curve even when random values were use for the data. Peer reviewed. Just recently, a paper was published that said more whales were getting worse and worse sunburns due to the 'ozone hole' letting in more and more UV. The reviewers somehow missed that the 'ozone hole' has been stable for years, and that UV rates have not changed in the last 15 years. There's other peer reviewed silliness, but that'll do  for now.



Jaydot's picture

Very interesting thread, thank you all for posting.

I'd like to add my very personal and completely unscientific experience: me and my guts simply feel much better after eating sourdough as compared to eating yeasted bread.

After eating yeasted bread, I get hunger pangs after two or three hours, and I can feel my blood sugar levels going wonky. After eating sourdough, I feel great.

Flourgirl51, why don't you just try both, and see if you can find out what your body tells you? Mind you, it might take your system a few days to get used to sourdough - it really is a very different product, due to the fermentation.

Oh, and I wholeheartedly second the suggestion to see what Andew Whitley says about it. He's written a good book on this subject.

flourgirl51's picture

Thank you for all of the great information. I still would like to know about how a person captures yeast from apple peelings and potato peelings and the methods and dangers of doing this if any.

flourgirl51's picture

So, does every method of capturing wild yeast result in a sour dough type of bread?

Mini Oven's picture
Mini Oven

I don't believe every method of capturing wild yeast results in a sour dough type of bread.   I think some of them fail and I think some cultures may grow the wrong wee beasties or none at all.   But I think certain methods and ingredients make it easier than others. 

Chuck's picture

From all the posts I've read here along the lines of "my sourdough doesn't taste sour enough ..." the only conclusion I can draw is that "natural" yeast isn't necessarily "sour".

I've seen various answers offered: leave the dough out longer, add "sour salt", revise the starter, get three witches around a cauldron...  It looks like if you desire "not sour" all you have to do is the opposite (or maybe nothing at all if you're lucky:-).

(I've also seen various posts about how to get a "sour" flavor without using natural yeast: using a bit of the previous dough that you saved, aging the dough a long time, not washing the container... There are even some comments in the book "Artisan Bread in Five Minutes a Day" about it being inevitable that the last loaves from a batch of dough will taste more sour than the first loaves.)

All that said, be warned that creating your own natural yeast starter may be somewhat tricky (IMHO, this is a second reason folks use commercial yeast). There are a lot of postings here along the lines of "I followed the directions, it's been two days, and there still aren't any bubbles at all". My personal theory is that industrial/urban air pollution makes creating a starter quite a bit more difficult than it was a century ago.

Jaydot's picture

"Capturing wild yeast" always has me envisioning people with aprons running around in a sunny orchard with a butterflynet...

Potatopeels bring along their own micro-organisms, which thrive around potatoes.
Cereals bring along the micro-organisms that thrive around cereals.

When making a starter, you want to cultivate certain micro-organisms that thrive around the cereal you prefer baking with. If you start off with other ingredients, you will still have to feed your starter and wait until the natural yeasts and lactobacilli that go with the cereal get the upper hand. If you start without other ingredients than flour and water, you'll also have to wait until the right natural yeasts and lactobacilli prevail.

I think "sourdough" is a rather unfortunate word, actually. Bread made with natural yeasts and long fermentation does not have to taste sour at all, if that's what you meant. It all depends on many variables that affect breadmaking: which cereal(s), the quality, temperature, hydration, etc.

clazar123's picture

Is this perhaps useful to you? At least as far as info on alternate sources of yeast for making bread.It is fascinating!

As far as the health benefits, there have been numerous discussions on this in the past 2 years. I've never seen much definitive that was well backed up by peer-reviewed studies. Well-being (good for you/everyone)is hard to actually define.What is good for you may be terribly unhealthy for me.

Yeast is ubiquitous to the planet and can be "captured" anywhere.Wherever you "capture" it from is generally where it likes to live-it gets food it likes and favorable growing conditions. The genus "san franciscus" of the famous San Franciso sourdough is actually very common in the San Fran Bay area and one other place that brings many imaginative scenarios to mind-human teeth/mouth.

So "sourdough" is merely a culture of  various yeasts and bacteria (can't catch just one thing in the microbial world-the neighbors tend to come along)that happens to taste sour. Different yeasts have different charactieristics and flavors. All eat and produce CO2, as far as I know, along  with other by-products.SOme like to eat fruit and some like to eat grain but they can cross-feed-just like we do, with varying success. Environmental factors we control such as feeding differently,starving,cold and warm all cause the yeast that favors those particular conditions to become dominant.

So all yeast produce "sourdough" but all sourdough tastes different-and much of it makes bread that tastes sweet.

Commercial yeast and sourdough both produce a risen grain paste that cooks into a loaf of bread but the by-products and processing of the components of the paste (at the cellular level) are probably much different. They really are apples and oranges. Whichever one accomplishes what you want it to is... good for YOU.

flourgirl51's picture

Thanks so much for this information. There is much to learn!

bpezzell's picture

I keep my liquid sour at 100% hydration. During heavy production I refresh by tripling. My leaven is typically a little less than 1/3 of the total weight of a finished dough. With that I get breads that have good grain flavor upfront and mild sour interest on the back of the tongue, almost as an aftertaste. My breads have been described as 'subtle' by a few of my favorite customers, with a shelf life of at least two weeks in our mild climate. A straight yeasted dough could never make it that long. The level of sour taste in a final dough seems to be more a function of feeding schedules, levain percentage in the dough, current climate conditions in your kitchen/shop, etc., than what specific strains of yeast or bacteria are active in that bucket of starter.

yogajan's picture

This has been an interesting discussion and well appreciated.  I would like to add to the comments about gluten intolerance and sourdough starter.  While there is certainly such a thing a celiac disease, it appears that gluten intolerance is the latest designer diesease.  Most gastroenterologists and indeeed the medical literature confirms that while some people are sensitive to gluten, it is in no way the epidemic that the media and many people would have you believe.  It is amazing to me that I can make my own sourdough starter, bake my own bread, eat it and am able to keep my weight stable and have less GI symptoms that I ever did when I ate commercial bread.  Frankly, we should be more concerned about the additives and preservatives in food than gluten.  (unless one has been thouroughly diagnosed with celiac disease).  Just my opinion, but it is an educated one.

CanuckJim's picture

I certainly do not have the background to add anything scientific to this very interesting thread; I just work with wild yeast starter on a daily basis.  The culture I'm using right now is ten years old and doing just fine, thanks.  I began it using unbleached bread flour milled from hard, red, spring wheat grown in Saskatchewan (13 per cent) and artesian well water with a fairly high trace mineral content.  I didn't add anything else: no organic grapes, lettuce leaves and so on, because I think that's all bunk, unnecessary and seems to spring from magic crystal land.  The starter wasn't fully mature until after about a month of regular feedings, with all the lactobacilli and other healthy bugs on board.  I live in dairy farming country, with lots of orchards around.  It must be fairly good, because I've shipped it (sub rosa) as far afield as France and California.

It isn't terribly sour, and I like to keep it that way; subtle is more like it, complex even.  However, I have experimented with other mixes to test the results.  Feeding a portion of the original with a proportion of whole grain wheat flour certainly yields a more sour mix.  Using a proportion of whole grain rye flour is more sour still.  I believe that this has to do with the higher percentage of grain sugars in these flours, and what I've read from Reinhart, Hammelman, et al, seems to back up this conclusion.  Once, I made a 100 per cent rye flour starter that was so very sour that I ended up tossing it; didn't like the flavour.

Mostly, this is all experience based and the product of observation and taste buds.  My two cents, anyhow.



Mini Oven's picture
Mini Oven

I just stumbled (re-read) a study; one observation, salt has the ability to change the microflora of the sourdough culture.  Lactobacteria growth was more sensitive to lower NaCl concentations than yeast.  (Page 5 last paragraph.)

Would it be possible to lower sour in dough simply by adding small amounts of salt to the starter?  Would adding salt early in the dough mixing lead to a less sour sourdough? Is delayed addition of salt, key in more sourdough flavor?

The study is Vol 64 no.7  in Applied Environmental Microbiology July 1998;  "Modeling and Growth of Lactobacillus sanfranciscensis and Candida milleri in Response to Process Parameters of Sourdough Fermentation"  in English.  Original in German

gary.turner's picture

The online pdf of this paper is here.



David R's picture
David R

... any recipe that has been turning out too sour,


... and you have some salt in your cupboard,


... then I guess the only thing preventing you from finding out the final answer is "Exactly how much salt equals a small amount?"


... and that question can't be that hard, can it? ☺️


- a couple of too-sour loaves, a couple of too-salty loaves, and you'll know for sure.

Randy Pollak's picture
Randy Pollak

The problem with commercial yeast products is they are ALWAYS being compared to sourdough products that contain LAB (lactic acid bacilli). It's apples against oranges! To be fair, if you wish to compare the health benefits of yeast versus yeast, there are NONE! Sourdough gains it's health benefits from the LAB not the yeast!

So what is you could add LAB to commercial doughs, could you get the same health benefits of sourdough? Of course you could! DON'T LET ANYONE TELL YOU IT CANNOT BE DONE! I've been doing it for years! For the LAB to do it's healthy job, you need only time. Minimum of 24 hours of fermentation! I use a method I call "low inoculation, long fermentation". Most of my "faux" sourdoughs are fermented for 72 hours or more. No sourdough starter is needed. Just a simple prefermentation of commercial yeast and Greek yogurt or water kefir. No feeding for weeks before use. In as little as three days I can produce breads and pizza dough with all the characteristics of sourdough! That includes the health benefits!