Sourdough – the Secret World of Acid and Gas

Some Beautiful Gluten Strands in a Sourdough Starter

Let’s discuss the character of sourdough a little – we often hear it described as a ‘wild yeast’, and we know that yeasts are fungi – a relation to forest mushrooms. But we also know that sourdough must also host bacteria, both good ones and bad, constantly doing battle with each other for dominance. And in a simplistic way, we also know that the yeasts and the bacteria must seek a peaceful co-existence -a symbiotic one- if our final baked bread is to be a good one.

But all of that is science stuff, and I’m betting that most of you are NOT scientists – and even if you were a scientist, chances are good that the science of sourdough doesn’t even fall into your arena of expertise – and you’re probably right there with the rest of us in our simplistic perspective on what’s going on chemically inside our loaf of sourdough bread. Most of us learn how to bake a good loaf of sourdough bread not through an understanding of the science involved, but rather through our own personal experience – in other words, by the seat of our pants.

And it’s the seat of my pants perspective that I’ll be describing here, since that’s what I know – or at least think I know – you may disagree with some of what I say here, and if you do, I hope you’ll join in our followup discussion via the comments section below.

The wild yeasts of a sourdough starter -to a bread baker- have one primary function: they provide the energy to turn your dense lump of sticky dough into a light, airy loaf of chewy, crunchy bread. Yes, a secondary function, but far less significant one, is to contribute to the bread’s development of flavor – but that task falls much more to the bacteria that have battled to dominance in the mix, as they acidify the dough during the fermentation phase – and that wonderful combination of characteristics is both a blessing and a curse to the sourdough baker.

OK, let’s get to it – what kind of practical baking secrets did I learn during my recent respite? Well, let me ask you a question: ‘What do you do with the sourdough starter that goes over-the-top?’ You know, the stuff that you meant to use, but forgot about. When I thought about that for a bit, and I realized that I was habitually throwing away a lot of old used up starter that I’d failed to use in a timely manner – and that got me thinking about the whole process of baking bread with a sourdough starter – and it suddenly struck me – throwing away used up starter is a very wasteful practice – isn’t there a way to avoid that?

Seemed like a good question to me – and I set out to find out if all bakers out there simply followed the crowd in this wasteful practice. Here’s what I found out.

When we bake with a sourdough starter, we’re taught to wait until the starter is in prime condition – and by prime condition, what is meant is prime yeast activity (as in the pic above) – the reason for this is so we’ll then have a strong proofing, or rising of the loaf. And that’s good advice – but we also keep hearing from our fellow sourdough bakers, ‘My sourdough bread isn’t sour!’ Why is that?

The answer is that the rising of our loaf is primarily the work of the sourdough yeasts in the starter, but the development of the tangy ‘sour’ taste in the bread is attributable to the growth of the various acids in the starter, primarily through the fermentation process of the starter’s principle bacteria (hopefully, Lactobacillus) . If both the yeast and the bacteria did their jobs at the same time and same speed, we’d then have a perfectly sour sourdough loaf. But the yeasts are faster, and so when they have accomplished their tasks, the bacteria is just getting started. If a baker pops the fully proofed loaf into the oven at the optimum time, chances are good that it has only just begun to take on the characteristic sour tang of a proper sourdough loaf.

What’s a baker to do?

Yes, there is a way you can have a sour sourdough bread, and still have it rise well – I discovered how by experimentation – you know, the seat of my pants. Instead of throwing out a used-up batch of old starter one morning, I simply used it just as I always did, but knowing that it wouldn’t contribute much to the proofing job, I added a a small amount of baker’s yeast too. Can you guess what happened? Yup – a beautiful light, fully risen loaf, with a tangy sour taste in every bite.

Yes, Bake in a Hot Oven, But Don't Forget to Lower the Temp on Entry! Still, I Love the Caramelization

Do you think this is cheating? Well lots of bread bakers who want a really sour taste in their sourdough don’t think so. In Eastern Europe, where there is a strong rye tradition, baker’s yeast has always been a part of the bread’s construction. If you want to Google it, you’ll find many other bakers using old starter for a flavor boost, just as even more bakers use a hunk of ‘old bread’ as an add-in to their next loaf. And -as a point of fact only- almost all sourdough breads done in mega-bakeries are made by using baker’s yeast for the rise, and dried acidified starter for the flavor component. (I think I’ll do some more experimentation by drying some of my own old starter, and then using it creatively, in biscuits, muffins, etc.)

I just thought you’d like a new perspective on using our starters occasionally just for adding flavor, and not having to worry about its ability to raise the bread as well. Frankly, I love the idea that sourdough starter is not quite as single dimensional as is commonly thought – and I love even more that maybe I don’t have to just pour it down the drain so often.

And if you simply must have a dose of scientific discussion on this subject, give these two sites a try.

http://www.thefreshloaf.com/node/10375/lactic-acid-fermentation-sourdough#comment-185862

http://www.nyx.net/~dgreenw/howdolacticbacteriaaffects.html

Or, for a gentler, reader friendly version – thank you, Azelia.

http://www.azeliaskitchen.net/blog/life-cycle-of-the-sourdough-starter-part-i/

Another Recent drfugawe Hybrid - a Rye, Whole Wheat Sourdough, From Fresh Ground Whole Grain

P.S. – I’m still learning about WordPress – Sorry!  I’m not sure I like this attempt to make the text of my posts a little bigger – bear with me, but expect more changes.
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About drfugawe

I'm a guy with enough time to do as I please, and that my resources allow. The problem(s) are: I have 100s of interests; I have a short attention span; I have instant expectations; I'm lazy; and I'm broke. But I'm OK with all that, 'cause otherwise I'd be so busy, I'd be dead in a year.
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8 Responses to Sourdough – the Secret World of Acid and Gas

  1. That looks sooooooooo good! I love the benefits of yeast and I enjoyed reading your knowledge of it. I always learn so much when I read your posts.

  2. Glenda says:

    Doc, I was thinking … When making a sourdough loaf, I usually build up my starter and throw out what I don’t need. Do you think I could keep the left over starter (unfed) and, when making the loaf, add it to the dough? It is 100% hydration so it wouldn’t affect the consistency of the loaf but may, as you suggest, add some flavour.

    • drfugawe says:

      Yes, I think that’d be perfectly OK – probably best kept in a closed container in the fridge – although if you’re going to be baking within a few days, stored out on the counter is fine too. Remember, that over time, it’ll build quite a bit of ‘sour’ and become quite acidic. Yeah, if your starter is 100% and you use 8 oz (or whatever # of grams that is), it’s simple enough to adjust the flour and water, 4 oz each. Yup, but don’t forget that if you do that, you’ll need some baker’s yeast for the rise.

  3. azélia says:

    hi Doc – nice to see you around again!

    I will post the definitions of Sourdough Types, I have so many things to post about and not enough hours in the day. It will show Sourdough Type I, which is what homebakers use, a pure sourdough culture to flavour and rise but the most common commercial one is Sourdough Type II which you describe above, with added baker’s yeast.

    A tip I give sourdough bakers if they want to make their bread particularly sourer is to add the old starter and mix in a lively starter but just under ripeness, a young starter, for the rise.

    In France I discovered last year a Pain Au Levain was officially allowed to have added baker’s yeast to the culture.

  4. drfugawe says:

    That’s a really good idea to use both old and new starters in a sourdough loaf – another variation to try – Thanks!

    Very interesting about the French willingness to ‘ease up’ on the legal restrictions re Pain Au Levain – maybe just catching up with the rest of the world – but I bet there’s quite a story behind that.

  5. Pingback: Sourdough Cinnamon Scrolls « Rhianna's Guide to Ethical Eating

  6. Pingback: Sourdough Bread « Rhianna's Guide to Ethical Eating

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