So what about those blisters you see on bread crust? No, it didn’t get sunburned! It turns out that blistering on bread crust is most commonly associated with sourdough breads. This is because acidic conditions created by sourdough breaks down the gluten near the surface. As the bread bakes, steam is created and it escapes through mini-chimneys all throughout the crust where the gluten has been weakened. Those mini-chimneys end up looking like blisters.
Interestingly, if you flour the surface of your bread, you will not really see any blisters. This is because the flour spread on the crust surface reinforces the gluten structure and prevents steam from escaping in that area. The loaf above had some parts of the crust floured and some was not. After brushing off the flour, I confirmed there were no blisters in those areas.
Blistering is really just a cosmetic feature which you either like or you don’t. It’s most commonly seen on sourdough breads, but you can also get blistering on any loaf that has built up more acidity. A long fermentation is one way to achieve this, even when using commercial yeast. Steam during the first part of the bake also encourages blister formation, while adding flour to the surface discourages it.
Happy blistering!
Why are blisters in a sourdough bread made with primarily bread flour most pronounced? Whole Wheat predominated doughs show little blistering? Why chemically?
Blistering is not really a chemical reaction, it is a mechanical action. It is gas escaping from weak points along the crust. Where the crust is weaker you see more blisters. Acid collecting on the crust in a sourdough or long-fermentation dough weakens it and causes blisters to form. If you coat the crust with flour, that extra dusting reinforces the crust and prevents blistering. Whole wheat is generally weaker to begin with, so you may simply not see the blisters because less gas is held in by all that weak crust. Or it could have to do with your… Read more »
sp is blistering a good sign? that means the gluten has been broken down, which we want, right?
I don’t think blistering is necessarily good or bad, it’s a matter of preference. Some like it, some don’t.