After kneading, the next step is the “bulk fermentation'', also known as the “first rise” or “rest” stage. This is where the dough matures, producing an enhanced structure to retain gas in the final rise.
Why prove bread twice?
The first stage matures the dough, whilst the second rises the bread to reach the right size for baking (full proof).
Bulk Fermentation = Creates flavour and conditioning properties.
Final Proof = The bread rises for the oven
What happens during bulk fermentation?
The dough fermentation process is created by the levain where carbon dioxide and ethanol are produced in alcoholic respiration.
Enzymes in the dough break down starches to simple sugars. These feed the yeast to continue to ferment whilst sweetening the flavour of the bread, making it more digestible and producing acids.
The acids created are largely lactic and acetic acids. But other “various organic acids” appear as well.
Is bulk fermentation essential?
We allow the dough to mature during the bulk fermentation stage in order for it to become a resilient structure. This is better for retaining gas. Bread that has been bulk fermented for longer will develop more flavour and aromas.
It is possible to make bread without a bulk fermentation. This can be with the use of preferments or by kneading intensely.
How long should bulk fermentation last?
Deciding how long to bulk ferment a dough is tough. There is no perfect answer, more a matter of “about right”. As factors of the dough improve, others deteriorate.
The diagram below displays how the properties of the dough change over time. and whether they are good or bad for the dough.
Some types of bread need the dough to be gassier than others before shaping so need a longer time. Others prefer a quick bulk fermentation. The underdeveloped dough will receive a bigger rise during oven spring.
Benefits of long bulk fermentation
A long bulk rise matures the dough making it better to retain gas and more full of flavour. This makes more interesting textures and tastes in the bread.
Enhancing the dough allows it to stretch and form big bubbles. This is characteristic of the best open crumb artisan loaves.
Bread benefits from a long fermentation time. But it is possible for the bread to deteriorate if it rests for too long.
Benefits of a short fermentation
Bread has more flavour and gas retaining properties when bulk fermentation is long. But quickly made bread doesn’t have to be bad. I actually quite like the lighter taste of shortly fermented bread when it’s well made.
Soft rolls enjoy a lighter taste and larger oven spring so need a short (or no) bulk fermentation. Croissants are relatively quick as you don't want the dough becoming gassy. It can be a nightmare to laminate with butter!
Fat is often added to fast breads as it masks the flavour of the underdeveloped flour. It’s common to add bread improvers such as malt flour and ascorbic acid to compensate for the lack of dough maturity.
How to adjust the time of bulk fermentation
Bread made slowly is often deep, interesting and extremely welcome. That said, other expectations must be met, otherwise fermentation activity will be too low - regardless of time. The factors that determine the length of the first rise include:
- The humidity
- Hydration levels of the dough
- Development of the dough during mixing/autolyse
- The levain used
- Amount of levain
- Amount of salt
- Oxygenation levels
Plus, the length of the final rise can also be a factor. If a long cool final proof is to be used, the bulk fermentation period should be relatively short.
How long does dough need to bulk ferment?
If we want a weaker crumb and less flavour then we reduce the rest time, but the final proof tends to be about the same.
For speciality artisan bread, an extended fermentation is achieved by using a fridge. Cool temperatures slow the rate of carbon dioxide production (alcoholic fermentation).
Using prefermented flour to make bread
Using a levain formed of prefermented flour accelerates the fermentation of the dough. It does this by introducing flour that is already mature.
Prefermented levains include Sourdough, Poolish, Biga and Pâte fermentée. Preferments raise the organic acids and carbohydrate development at the start of mixing. This lowers the length of time required to make the bread. You can find out more on the what is a levain page.
Bulk fermentation in the fridge
Cooling the dough slows down the production of gas and allows the dough to develop sweet and interesting flavours. Many bakers also use it to help manage their timings and ovoid early starts. The typical fridge fermentation is overnight - about 10 hours.
Some bakers use the fridge to store a large batch of dough to bake off fresh every day.
Stretch and folds
The dough should be turned every hour (or so) to allow the temperature and the sugars/yeast to be redistributed.
A technique called “stretch and fold” redistributes whilst also stretching the gluten.
It helps the gluten network strengthen and accelerates the rate of levain activity during the bulk rise.
When is the doughs bulk fermentation finished?
The bulk fermentation can end once the gluten is strong enough to be shaped and there is some gas activity.
Deciding when to end bulk fermentation
Before we reach the stage of over fermenting, there will be a noticeable deterioration in some areas whilst others improve.
There is never a “perfect” fermentation time as when we ferment for longer, extensibility and oxygenation increase. We also may have other constraints like preventing oven bottlenecking. We have to “take a view” on when it is best to end bulk fermentation.
Extensibility of the dough
Extensibility is the power of the dough to stretch without tearing. We can increase the extensibility of the dough by:
- Autolysing without salt
- Selecting flour with high amounts of gliadin
- Hydrating the flour correctly
As you can see from the diagram as the dough continues to ferment it creates more lactic acid which results in the extensibility decreasing.
This is where flour latches on to oxygen that it comes in contact with. A little bit of oxygenation is great for the bread as it helps to strengthen the bonds in the dough. But too much and it washes away minerals and flavour.
Over oxygenation is likely to happen when bread has been mixed intensively and a long bulk fermentation is used. You can find out more on the oxygenation page.
Over fermenting dough
Sometimes, whilst our dough is bulk fermenting we decided to go canoeing and get caught in a tidal drift. On our delayed return, we’re too late and the dough is over fermented.
Over fermented dough is gassy, full of uneven bubbles and collapses with the slightest touch.
How does dough over ferment?
A dough is over fermented once the yeast has eaten all the available sugars. It burns out and gas production is reduced severely.
Over fermented dough is too gassy to mould properly. A weak, uneven crumb structure is common and tends to have an extra strong whiff of alcohol. Extra ethanol is created which will remain in the bread after it is baked.
How to fix over fermented dough
If the dough is over fermented there is no way to reverse it so I recommend baking it straight away without any shaping. Hopefully, you will end up with a rustic style bread, similar to a Campaillou loaf.
Over oxygenation usually occurs alongside over proofing. It diminishes the flavour and colour of the bread.