Why is my bread now deflating when I slash vents before baking?
I make bread once a week from the same sourdough starter, which lives in the fridge between feedings. On the day before baking day I take it out, feed it, wait until it's fully active, take some of that for the levain, and put the rest back in the fridge.
For the last two weeks, my dough has risen overnight as expected, and then again after shaping, but when I've gone to slash the vents right before baking, both times it deflated somewhat (about 15-20% I'd guess). It then rose back up in the oven ("oven spring"), but unevenly -- the top was a little lumpy from the unevenness caused by the deflating. I've never seen this behavior before. The resulting bread tasted fine and had about the amount of crumb I'm used to (maybe a little finer, but within normal bounds).
I usually bake white breads, though I've made rye and whole wheat loaves before. Both of these were rye -- two different recipes, one new and one that I've made before. I don't know if the type of bread is relevant.
I'm not aware of any significant environmental changes. The weather has gotten warmer here during this time, but I baked bread last summer too and we're not yet into the very hot part of the year.
What might be causing this new behavior, and what should I do to correct it? I'm open to experiments, though I'd like to keep the rate of total baking about the same as it is now.
1 answer
If cooking is chemistry, baking sits on the border with biology.
Factors that could be an issue:
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humidity in your refrigerator
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humidity in your kitchen
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the current balance of yeast to bacteria in your starter
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the activity of your starter, which is both temperature related and just based on how happy those microorganisms are
The rise of your bread is determined by the amount of carbon dioxide released during fermentation of available starches, the distribution of those bubbles in a gluten network, and the timing of the two. I hypothesize that a slightly warmer kitchen has led to an earlier peak in CO2 levels, which formed larger bubbles. When you slashed the tops, more CO2 was released than usual and the bubble-caverns collapsed more than usual. Note that rye has less gluten in it to begin with than wheat, more free sugars (so fermentation produces more CO2) and more amylase to break down starch into sugar (so it will get sticky faster than wheat).
You might want to try:
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rise your rye dough in a cooler place
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add a small amount of white vinegar or lemon juice to your recipe. Acidulation reduces amylase activity, and as a result, lots of rye bread recipes incorporate some vinegar
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reduce any sugars you add to the rye dough
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use slightly less of the sourdough starter, as this will cause the bread to rise more slowly and have smaller bubbles
Good luck!
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