The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

How does sourdough work?

Lazy Loafer's picture
Lazy Loafer

How does sourdough work?

I was browsing through article on the web about the science of bread and sourdough, in preparation for my upcoming Sourdough Bread Basics course (which I'll be teaching in my home). I wanted something based in science that was understandable and easy to communicate to a variety of people. Some articles are thorough but very technical, while others are too simplistic and skip over some important stuff (leading to more questions).

I just found this article, which is so good I thought I'd share it here for others. :) I deals mostly with the affect of sourdough bacteria on wheat gluten, but gives a very good description of wheat proteins and how they act.

Danni3ll3's picture

I learned a lot. It explains why one of my friends can eat einkorn breads and another cannot. Thank you for sharing.

Lechem's picture
Lechem (not verified)

That the first results are in from the sourdough starter project going on and while there are other strains if yeast within starters by far the most common is bakers yeast. And this goes for starters around the world.  

I think what makes starters unique is not the yeast but rather the lactic and acetic acid producing bacteria.  

Lazy Loafer's picture
Lazy Loafer

And I was fascinated to find the overwhelming commonality around the world - S. Cerevisiae wins by a huge margin! It's funny how some people insist that their bread be leavened with sourdough because they have a 'yeast infection' and somehow active dry yeast is evil. So far I have refrained from pointing out that the world (including people) is covered in yeasts. Now I will have to also refrain from saying that common baker's yeast is pretty much what is in the sourdough as well (not to mention that it is certainly dead by the time the bread gets to the consumer).

This also supports the use of a little bit of dry yeast to boost a sourdough bread. You get all the benefits and flavour from the bacteria in the sourdough and a little more yeast to help it rise!

MonkeyDaddy's picture

after 26 years working in the ER, the crazy misconceptions that people walk in the door with.  It can be quite hilarious (and often pathetic and sad).

S. Cerevisiae works wonders when given plant-based polysaccharides to digest, but given the fact that the stuff is literally everywhere, by the logic your customers give, everybody on the planet would probably be consumed by it if it liked living on human flesh.

And, going the other direction, although I have never tested it and never will (yuck) I'm pretty sure that Candida albicans, the organism responsible for "yeast infections" (since it does prefer humans to plants) would likely not be a suitable candidate for breadmaking.

Have your customers ever asked what strain of yeast lives in your sourdough culture?


Portus's picture

that still has me confused, but now at a much higher level :-)  Thanks for sharing!

Doc.Dough's picture

A couple of years ago I set out to affirm the oft stated claim that you can't start a sourdough starter from baker's yeast.

So I mixed up a little yeast, water, and flour and kept feeding it every 24 hrs assuming that it would at some point stop growing and go dormant while competing organisms began to take over.  To my surprise, after a couple of weeks I smelled something that was more like sourdough than baker's yeast and when I checked the pH it was 3.8-ish and growing just fine. In another couple of weeks it was indistinguishable from my King Arthur starter of many years in terms of growth profile and acidity.

I repeated the experiment with more careful isolation and got the same result.  So now I suggest to folks who want to start a starter to use this technique instead of the pineapple juice solution that I had been recommending for a number of years.  I have had no reports of failures in a dozen or so tries.

It is worth noting that not all of the samples tested were dominated by baker's yeast so there are other stable starters (stability is another somewhat contentious topic that deserves a separate thread) based on different dominant yeast strains.