One of the biggest challenge a baker has to overcome in sourdough bread baking is to predict when the sourdough has completed proofing, to avoid underproofing and overproofing. The ability to judge when the dough is done proofing will result in a far superior and consistent bake.
These are some of the key questions about sourdough proofing and overnight retardation that we will be discussing :
- What happens to the sourdough during proofing?
- How do you tell if your sourdough is done proofing?
- What temperature and time should you proof your sourdough?
- What happens when you overproof your sourdough bread?
- What happens when you underproof your sourdough bread?
- What does overnight proofing in the refrigerator does to your sourdough bread?
- How long can I leave the dough to proof overnight?
What happens to the sourdough during proofing?
Proofing is simply another word for fermentation, it is the time given for the yeast and bacteria in your dough to undergo fermentation and produce gasses that allows the dough to rise. Proofing plays the biggest role in determining the volume, crust and crumb structure of your sourdough bread.
Proofing happens in two stages throughout the baking process. The first stage is commonly called bulk fermentation which takes place after the dough has been mixed. The second stage is called final fermentation which takes place after the dough has been shaped. The combination of the two stages of proofing typically makes up about 80% of the total baking time.
How do you tell if your sourdough is done proofing?
The main objective of proofing your dough is to wait for carbon dioxide gasses to accumulate and rise the dough; the dough has done proofing when it achieves a 30% rise during bulk fermentation, and an additional 30% rise of the dough during final fermentation.
We can easily observe the percentage rise of the dough during bulk fermentation by placing the dough in a transparent square container that has the same width throughout its height, and measuring the rise with a ruler.
Place a tape or a rubber band around the container to mark the top of the dough during the start of bulk fermentation. Then we can simply use a ruler to measure a 30% increase in height of the dough, which corresponds to a 30% increase in volume of the dough.
It is harder to measure the rise of your dough during final fermentation as the dough has been shaped and now rests in the banneton. There are two ways we can determine if the dough has done proofing at the final fermentation stage, the first is to eyeball the rise, and the second is to do the poke test.
Soak your finger in water so that the dough does not stick to it, and poke the dough about 2cm deep. If the dough springs back immediately, it still needs more proofing time. If the dough springs back slowly and your prod leaves a small indentation, it has done proofing. If the dough does not spring back, it has overproofed.
What temperature and time should you proof your sourdough?
With a 10% innoculation of a strong sourdough starter (a 100% hydration starter that doubles in size every 4 hours at 25 Celcius), the white wheat sourdough that is proofed at 25 Celcius will be done proofing after 4 hours for bulk fermentation and an additional 4 hours for final fermentation.
Proofing time is dependent on 5 factors, the proofing temperature, the quantity of your starter (innoculation), the strength of your starter, the type of flour, and the degree of handling during bulk fermentation. Proofing time only approximates when the dough has done proofing, the dough will have completed proofing once it rises 30% during bulk fermentation and another 30% during final fermentation.
Proofing time is dependent on the temperature of the proof. For every 2 Celcius increase in proofing temperature, proofing time will decrease by 1 hour. As the temperature increases, fermentation in the dough ramps up, gas production increases and you will achieve the 30% rise in your dough in a shorter time.
Proofing time is also dependent on the quantity of your starter (innoculation). As an example, a 10% innoculation would mean the flour in the starter consists of 10% of the total flour of the final dough. As you increase the percentage quantity of the sourdough starter in the final dough, there are more microbes that carries out fermentation, leading to a 30% rise in a shorter time.
Proofing time is also dependent on the strength of your starter. The timings given is only valid if your sourdough starter doubles every 4 hours at 25 Celcius. If your starter takes a longer time to double in size, it means that it is weak, and hence it will take your sourdough a longer time to achieve the 30% rise.
Proofing time is also dependent on the type of flour that you use. Sourdough bread made with rye flour is the most active, and hence has the shortest proofing time to achieve the 30% rise. Sourdough bread made with wheat has moderate fermentation rate, while spelt has the slowest fermentation rate, requiring a longer proofing time to achieve the same rise.
Proofing time is also dependent on the degree of handling of the dough during bulk fermentation. Different recipes call for different methods of developing your dough during bulk fermentation, some common techniques includes the stretch and fold, coiling and lamination. The more you handle the dough during bulk fermentation, the more the dough is degassed, and hence it decreases the percentage rise of the dough. The dough that has been handled more frequently, would need a lower percentage rise to indicate when proofing is done.
What happens when you overproof your sourdough bread?
An overproofed dough has weakened gluten matrix due to the acidity and protease degrading the gluten over time. The pressure build up from the carbon dioxide gasses starts rupturing the weakened gluten network, releasing the gas and deflating the dough.
In extreme cases, when the dough bakes in the oven, the gluten will be so weak that the crumb splits into two halfs, resulting in a giant hole in the crumb structure underneath the crust.
An overproofed dough can be saved by saved by removing it from the proofing basket, pressing it down firmly, reshaping it and returning it to the proofing basket. The stretching and folding when reshaping the dough rebuilds the gluten matrix to enable the dough to trap gasses again.
The dough can then be baked as usual once it has risen by 30%, and if it has passed the poke test. The resulting baked loaf will have a good rise and volume.
If your dough no longer rises anymore, which only happens if you have left the dough to overproof for many many hours, do not throw the dough away! Yes, it will not make bread with good volume, but it will still serve as an excellent flat bread, for example a pizza crust.
What happens when you underproof your sourdough bread?
An underproofed dough does not have insufficient time to inflate all of its gluten cavities with carbon dioxide gasses. There will be too little pressure build up inside the dough, causing the dough to be flat. When it is baked, it will have poor oven spring, and large tunnels near the surface of the crust.
An underproofed dough can easily be saved by giving it more time to ferment and produce the carbon dioxide gasses required to give it a good rise. Do not be afraid to add an hour or two to your bulk fermentation and proofing time if the dough has not sufficiently risen by 30%, or if it fails the poke test.
What does overnight proofing in the refrigerator does to your sourdough bread?
Overnight cold retardation in the refrigerator takes place after you have shaped the dough and place it in the banneton; it replaces the final fermentation step in the baking process.
The cold temperature in the refrigerator slows down yeast fermentation dramatically, while lactic acid bacteria continues to release acid into the dough. The build up of acidity increases the structural strength and sourness of the dough and imparts a complex flavor profile to the baked loaf.
One advantage of overnight proofing in the refrigerator is that it allows the baker to delay the baking process, hence the baker can bake the bread at a more convenient time.
Baking a sourdough bread takes up about 10 hours in the day, and requires the baker to start the process early in the day if they would like to finish baking by day’s end. Cold retardation allows the baker to complete a part of the baking in the first day, load the dough into the fridge, and resume baking the next day when time permits.
How long can I leave the dough to proof overnight?
Your sourdough is typically left to proof in the refrigerator for 10-12 hours, and up to 24 hours with no adverse effect on the dough. After 24 hours, the dough will get too acidic, and the resulting bake too sour for taste.