January 21, 2007 @ 1:41 pm | Filed under:
Science I seldom cross-post, but I posted this on the bread blog today and thought it might be of interest to my Lilting House readers too:
Jane and I are exploring the science behind the sourdough loaves we’re baking. Found this fun site: The Science of Cooking. An excerpt from the sourdough page:
In addition to flour, water, and yeast, your starter also contains
bacteria. When these bacteria feed on the sugars in flour, they produce
acidic by-products. This is what gives sourdoughits sour taste.
Actually, all doughs contain at least some bacteria. So why aren’t
all breads sour? In doughs made with bakers’ yeast (the kind you buy in
the store), the yeast outnumber the bacteria. Since both compete for
the same sugars, the yeast win out, and the bacteria don’t have a
chance to produce their acidic by-products. In sourdough, yeast and
bacteria are more closely balanced, so the bacteria have a chance to
add their flavors to the bread.
Sourdoughs and other raised breads also differ from one another
because of the eating habits of the yeasts that make them rise. The
predominant yeast in sourdough, Saccharomyces exiguus, cannot
metabolize maltose, one of the sugars present in flour. Baker’s yeast,
on the other hand, has no trouble feeding on this sugar. Since the
bacteria that give sourdough its taste need maltose to live, they do
much better in the company of sourdough’s yeast because they don’t have
to compete for this sugar.
Other links:
Wikipedia on sourdough
How Stuff Works on sourdough
The history & microbiology of sourdough
That Science of Cooking site has a lot of other neat stuff. The candy page is especially interesting. We might just have to do a unit study on candy one of these days…chemistry AND physics! (And with sourdough we’ve got biology too.)
Hmm, the high educational value of this topic might make it a good post for Lilting House.
Jane and I are exploring the science behind the loaves we’re baking. Found this fun site: The Science of Cooking. An excerpt from the sourdough page:
In addition to flour, water, and yeast, your starter also contains bacteria. When these bacteria feed on the sugars in flour, they produce acidic by-products. This is what gives sourdoughits sour taste.
Actually, all doughs contain at least some bacteria. So why aren’t all breads sour? In doughs made with bakers’ yeast (the kind you buy in the store), the yeast outnumber the bacteria. Since both compete for the same sugars, the yeast win out, and the bacteria don’t have a chance to produce their acidic by-products. In sourdough, yeast and bacteria are more closely balanced, so the bacteria have a chance to add their flavors to the bread.
Sourdoughs and other raised breads also differ from one another because of the eating habits of the yeasts that make them rise. The predominant yeast in sourdough, Saccharomyces exiguus, cannot metabolize maltose, one of the sugars present in flour. Baker’s yeast, on the other hand, has no trouble feeding on this sugar. Since the bacteria that give sourdough its taste need maltose to live, they do much better in the company of sourdough’s yeast because they don’t have to compete for this sugar.
Other links:
Wikipedia on sourdough
How Stuff Works on sourdough
The history & microbiology of sourdough:
Sourdough culture is a yeast living symbiotically with a friendly
lacto-bacteria. We need to start with enough of the right organisms so
that they can become the dominant culture, food and water and the right
temperature.
Given the right organisms, the optimum temperature is just
over 80F/27C. Much hotter and the activity of the yeast declines. Above
95F/35C the yeast is effectively dormant or dead. The bacterial
activity peaks at 93F/34C, so some bakers choose to ferment at 90F/32C
to get a sourer bread. At 70F/21C the activity of the yeast has roughly
halved, so the fermentation will take twice as long.
I’ve been meaning to put together a post containing the various links helpful people have sent me since Jane and I began this blog. I really appreciate all the great advice you folks have sent my way—thanks so much!
Someone (sadly, I cannot remember who) recommended this site: The Fresh Loaf, a vast collection of articles and links about all aspects of bread-baking. The site also includes a discussion forum where newbies can post questions for more seasoned bakers to answer.
Some articles on this site that particularly caught my eye:
Wild Yeast Sourdough Starter (how to make your own starter using flour and pineapple juice).
Getting a Sourer Sourdough
Deluxe Sourdough Bread recipe
Why Yeasts Attack (background info on sourdough baking; good walkthrough with pictures)
More About Sourdough (part two of the above)
Lesson Two (step by step instructions for yeast bread, not sourdough)
Domenico Bettinelli left a link to a much-discussed NYT article about a slow-rise, no-knead method of breadbaking. You need an NYT account to access the article, but there is a video demonstration here.
I continue to spend a lot of time on Teresa’s Northwest Sourdough site and blog. I really appreciate her detailed walk-throughs with pictures. (And I can now testify as to the scrumptiousness of bread made with her NW Sourdough starter!)
January 21, 2007 @ 10:06 am | Filed under:
Sourdough …in baking a really fine loaf of sourdough bread.
It isn’t a perfect loaf, but it’s a vast improvement upon our first two attempts with sourdough, and it tastes really, really good. The crust has a nutty flavor so delicious we can’t stop breaking off little bits for "just one more" taste.
The recipe we used calls for a starter at 166% hydration, which is to say: maintained with one part flour, two parts water. We had to figure out how to adjust it for a 100% hydration starter (maintained with equal parts flour and water) because—and I know this is a little silly but we don’t care—it is such fun to have a nice thick starter bubbling in the crock a little too vigorously so there’s always that danger it will overflow. For the same reason, I don’t want to keep the crock in the fridge even though we aren’t yet baking enough to justify feeding a starter daily. We don’t care. Flour is cheap. We’re having fun.
Jane says she still likes baking yeast breads best, because there is so much more kneading. We’re going to shoot for one sourdough baking and one yeast bread baking each week. I’m so grateful to JoVE, whose post inspired us to start!
Things we need to figure out:
• The recipe said to proof the dough in a bowl lined with a proofing cloth sprinkled with flour. No problem there, but how do you then transfer the dough to your baking stone without deflating it? Ours was a pretty oozy dough (don’t know the right terminology)—not firm like our honey wheat yeast bread dough has been—and by the time I got it onto the stone, it was a big flat blob and I was sure it was going to be a complete flop. It did rise more in the oven, though, so we wound up with a nice big round loaf, a little dense but not a bad texture at all. But still, there has got to be a better way to make the switch. I wish I could watch a real baker do it. I have no technique.
• The slashing! Why can’t I get this right? I even got the special bread slashing tool. I’m too timid with my cuts. I don’t go deep enough. Again, I think it would help to see someone do it. But I guess I just need to cut deeper, with less hesitation.
