This is a part of an in depth 'beginner's guide to sourdough baking' from CooklyBookly founder Freddy May. Click here to see the full collection. Feedback is very welcome, so please send comments to firstname.lastname@example.org.
What is proofing?
Proofing is the final stage before baking. You are now giving the dough the chance to do its last bit of rising after it has had its final shape. Basically, it's allowing the dough to ferment still further to the optimal baking point.
As with the fermentation, I let my dough rise by about 70%. The optimal timing might vary so I suggest you experiment and see what amount of proofing delivers the best rise (oven spring) for you.
The poke test
A well known way of checking is to push your finger into the dough up to the first knuckle. Do this on a floured spot or your finger may get stuck. When you pull your finger out watch how the indentation pushes itself back out. It should come back out about half way if it's ready. If it stays all the way in, it's over proofed. If it comes all the way back out, it's underproofed.
If your dough hasn't fermented enough then the gas bubbles, the by product of fermentation, have not had enough time to develop. The fermentation process has not had enough time to break down the gluten, which will remain too strong.
As a result, when you bake, the gluten is resists the expansion of the underdeveloped bubbles and you'll end up with a dense crumb. The more under proofed, the denser it will be.
Over proofing means that the acidity in the sourdough will have broken down the gluten too much. As a result, when you bake, the bubbles will indeed expand but there will not be enough strength in the dough to prevent the bubbles from bursting, resulting in a collapse of the structure. Again, your bread will be dense, but a different kind of dense!
Is it better to under or over proof?
Given that it's almost impossible to say whether your dough is 100% perfectly proofed you are always going to end up a fraction under or over proofed. In my opinion, it is better to under proof a tad than over proof. Experience will tell you when it's time to bake. You have a good window of opportunity with sourdough because things move so slowly.
I have learned a lot more from my failures than successes. Try to remember what you did along the way. Did you perhaps give the ferment not enough or too much time? Same with the proof.
Using the fridge
I often put my banneton or bowl into the fridge for the proof. It's a great way of controlling timing and doesn't make you a slave to your bread.
You can let the dough proof at a warmer temperature for a while or you can put it directly into the fridge. You just have to be aware that you need to allow a lot longer for the proof if you refrigerate throughout. You will have to experiment a bit to figure out what works best for you and your dough.
You'll also notice a real difference in taste if it has had a cold proof. The taste will be deeper and somewhat sourer.
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