The Fresh Loaf

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Good eGullet Sourdough article

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JMonkey's picture
JMonkey

Good eGullet Sourdough article

I was poking around eGullet this morning when I happened upon an excellent sourdough article that really helped things click into place for me, at least mentally. I'm going to be travelling for a bit and so won't get back to the kitchen for sometime.

What Jim has been saying about time, temperature and the percentage of starter in a dough made sense to me, and has helped me improve my bread (thanks!), but I still didn't understand a few things. For instance, I know that I've had a more sour bread when I retard it in the fridge, but I've also had a more sour bread when I increased the proofing temperature to about 82 degrees. Why is that?

This graph from the article, I think, might help explain it. I realize now that it's a version of the graph that Jim posted, but at the time, I didn't realize that Candida Milleri in Jim's graph was yeast.



The key factor, if I'm reading the article and Jim right, is not necessarily the level of activity, but rather the respective levels of activity between the yeast and the bacteria. At room temperature (about 70-75 degrees F), for instance, the yeast and bacteria are roughly equal in activity. However, on the edges -- lower than 70 degrees and higher than 75, bacterial activity outpaces yeast activity.

Here's what the authors say:

The right temperature is the single most critical variable. Michael Ganzle and his co-workers did some studies on this. They found the following growth rates of L. sanfranciscensis and C.milleri as function of temperature. Growth rate is ln2/generation time, i.e. a growth rate of 0.7 is a generation (doubling time) of about 1 h.

The generation times measured in laboratory media are different from that in rye / wheat / white wheat dough. If the generation time at 20 C is 1/2 of that at 30 C in my medium, the organism will also grow 1/2 as fast at 20 C compared to 30 C in dough (we checked). So, it's not the absolute numbers that matter, but the ratio of growth rate to growth rate at optimum temperature.


There are a ton of other variables, of course -- the proportion of bacteria to yeasts in the starter, the species of yeasts and bacteria in the starter, etc -- but might this explain why both retarding the dough at a low temperaure and fermenting at a somewhat elevated temperature (~82-85 F) would produce a stronger sourdough than fermenting at room temperature -- because the bacteria are more active than the yeast?

Anyway, interersting article. I'd be interested to hear what others think. Is that your take, Jim? I think I'm finally wrapping my head around this stuff ....
jm_chng's picture
jm_chng

Hi JMonkey,Sorry it was Ganzle not Dan Wing. Thanks for linking that. The problem is if you compare the two graphs, the one I did based on data at the rfs and the one above, you'll se in mine there's two types of lb's, and just one yeast, there could be five different yeasts and maybe two lb's in yours and mine. We don't know this for sure. You are right in the above case there is a difference in the growth rates below 21 C and above which is what I said in my article, but the difference can be blurred considerably if you have a complex starter. Here's a link to a file I made to show what could go on. This is not based on real data.
Oh, sorry, that didn't work I can't post pdf's and I can't convert pdf's to jpg at work I'll have to post it later when I get hom. but just imagine the yeast shifted to the left a tad.
Jim

JMonkey's picture
JMonkey

Jim wrote:

The problem is if you compare the two graphs, the one I did based on data at the rfs and the one above, you'll se in mine there's two types of lb's, and just one yeast, there could be five different yeasts and maybe two lb's in yours and mine. We don't know this for sure. You are right in the above case there is a difference in the growth rates below 21 C and above which is what I said in my article, but the difference can be blurred considerably if you have a complex starter

Yes -- that's the beauty and the frustration of sourdough, because, for the vast majority of us, it's still just this side of alchemy. My own starter could be very different from yours, and, since I feed it fresh ground whole wheat, it could be changing from week to week, month to month, with all the critters hanging around on my wheat berries.

But even this one graph of two of the many species I could have in my stuff seems to explain the phenomena I've observed in my own kitchen. I hope it helps me make better bread.
jm_chng's picture
jm_chng

How long have you been making sourdough? 

Jim

JMonkey's picture
JMonkey

I've been making sourdough about a year, but I've packed a lot of baking into those 12 months. I bake all my family's bread, and since August, for instance, we've gone through 100 pounds of wheat berries. Thank goodness they're cheaper than dirt (well, cheaper than high-quality potting soil would be more accurate, but I'm quibbling).

I feel very good about where my white sourdough is. I can consistently get a strongly flavored loaf with an open texture and a crunchy crust. Unfortunately, I rarely bake white breads.

On a weekly basis, I usually make a couple of loaves of whole wheat sourdough sandwich bread, which I'm also pleased with. I've got the flavor and texture I'm looking for.

Where I want to go is:

  • Figure out how to make a tasty, lean 100% whole wheat sourdough hearth bread: No-knead isn't working well at all for whole wheat. I get a great crust, but a relatively dense, flat loaf. It may be that I'm trying to go too high on hydration and the loaf is spreading? (that last failure was at 85%). And when I make it the traditonal way, the crust tastes ... burnt? Maybe it's the bran? I dunno.
  • Figure out how to make a well-flavored sourdough pizza crust that's got a significant amount of whole wheat. I'm just starting on this, so naturally, my first effort was a bust.
  • Figure out how to make a no-knead whole wheat sourdough loaf that I can set up in the morning and bake after I get home from work. Not a huge goal, but if I can figure it out, I'd be a happy dude. Nowadays, I bake on the weekends and freeze it for use later in the week, which is OK, but nothing beats fresh bread. I wonder if the oil and honey that I add to the sandwich bread dough prevents the dough from "kneading itself" well enough? Who knows?
  • sewwhatsports's picture
    sewwhatsports

    for those of us uninformed, what is is r.f.s?  I already feel like a neophyte here so this is not helping <g>.   

    Rena in Delaware

    sphealey's picture
    sphealey

    r.f.s (note small case, not caps) is the old Usenet newsgroup rec.food.sourdough

     

    You can find it via Google Groups if you are interested. It carried forward to Usenet from the old netnews, has been around a looong time, and is still active.


    But like most Usenet groups still operating, it is populated by True Fanatics(tm). Unlike here of course.

     

    sPh

    JMonkey's picture
    JMonkey

    That's a really good description. Many of the folks there just about secrete lactobacilli and wild yeast from their pores, they know so much about sourdough. But they do not suffer fools easily, and the bar for what passes as a fool there is very low. I'd not recommend that a new sourdough baker go there for help unless that person has skin of asbestos. I enjoy reading the posts, and occasionally posting myself, but it's definitely not for everyone.

    alconnell's picture
    alconnell

    I have subscribed to the www.bread-bakers.com digests for several years.  Informative and low key - not like the UseNet groups. 

    Kate's picture
    Kate

    I really, really like my sourdough pizza dough - I think it's the best pizza dough I've ever had - and I've just started putting whole wheat flour in it. The last time I made it 1/4 of the flour was whole wheat and seemed like it could have taken a lot more. Here's the recipe if you're interested: (This is a half recipe - I usually make a large-ish pizza and bread sticks out of this much)

    8oz bread flour (or combination of bread + whole wheat)

    3/4 cup water

    3/4 tsp salt

    2oz sourdough starter

     

    Mix flour + water together for a few minutes, let rest for 10. Add salt + starter and knead (I use a mixer w/dough hook for 10 minutes). Let rise until doubled (takes my yeast 8 hours over the winter). Before shaping into a disk I cut a few slices off to make some bread sticks, and recently I have added dried rosemary and oregano to the dough before kneading. Yum!