How important is fermentation in baking bread?
It’s easy to learn to bake bread and not understand what is actually going on during fermentation. Then again, it’s easy to be a professional baker and not know much about it either!
If you're reading this post it’s likely you’re capable of following a bread recipe, it'll probably confuse the life out of you if you have no baking experience -if not, leave a note in the comments- but let’s explore this topic in more detail.
Fermentation is the kingpin of bread baking, so what is going on?
"Fermentation is the stage where the ingredients in the dough develop before being placed into the oven. Two types of fermentation occur.
The first is the action of yeast or other levain breaking down the sugars in the flour.
The second involves the development of flour which reacts with the water.
The combination of both types of fermentation create a great textured dough which rises."
Why is bread fermentation necessary?
A mass of flour, salt, levain and water is the beginning of a dough. To make bread the flour needs to develop some characteristics.
It needs to be able to retain gas, create flavour, be capable of becoming shaped and have some keeping quality.
Failure to ferment a dough or to not allow a long enough period to fully ferment lowers the dough's ability to inhibit these characteristics.
That’s not to say you can’t make a bread without a full fermentation period, it just means it will most likely be…. crap.
….Or in need of some artificial enhancement.
In general a longer fermentation period is preferred as it’ allows the dough to reach its full potential. We can speed up the fermentation time by mixing, including stretch and folds, changing the levain amount and increasing temperature.
But it’s not just the length of time, it’s the quality of conditions and technique from the baker that make a difference to the finished product.
All of which I’ll explain in more detail in this post.
The two types of bread fermentation
Let’s take a look again at the two things that happen during the fermentation of a yeasted bread, this time, in more detail:
- The yeast breaks down the starch found in the flour creating ethanol and carbon dioxide.
- Whilst the flour reacts with water to soften the protein into strands of gluten. The end result is to a matrix suitable to retain the gas produced.
So gas is created and then retained in the dough. This makes the dough expand, or as it’s commonly called, rise.
Flour is hydrated by the water and naturally turns into glutamine and glyadin. Collectively they’re called gluten. But there are two different types of gluten created.
Glutamine makes the dough hold its shape and glyadin allows the dough to stretch without ripping.
Both are essential for bread making, some recipes call for a dough with more glutamine like ciabatta.
Some desire more glyadin, for instance a baguette baker.
Whilst the flour ferments, the yeast gets to work and produces carbon dioxide. The gas gets trapped between the strands of gluten and forms pockets of air.
The pockets expand and the dough rises. So the combination of the two types of fermentation work together, one creates a structure, the other utilises this structure and raises the dough.
The ethanol produced is not really necessary for bread production. Most of it evaporates once baked but leaves an odour. This is prominent in heavily yeasted bread which is often overpowering with ethanol and masks the flavour of the flour.
In longer fermented bread the smell can be deep, interesting and extremely welcome.
The whilst ethanol is not essential, it does have a neat advantage that improves breads keeping quality. Its inclusion alters the ph factor of the dough which helps prolong its freshness and become resistant to mould.
Quickly fermented bread can often include a dash of vinegar to replicate this but it’s not the method an artisan would follow.
The bakers best friend, Gluten
Gluten is visible as the stringy state that the dough forms. As a dough is kneaded the more noticeable it becomes.
It’s what makes it stick to your hands and table!
Gluten is generated from the protein in the flour and is what gives bread it’s crumb network to retain gas.
A dough with high gluten content uses a flour that has a high ratio of protein.
Poor quality flours contain broken or low quality proteins do exist. Despite often having a high protein content, these flours create a weak gluten structure.
A strong dough has a good gluten structure, created from a good quality flour that's been properly fermented.
A strong dough is bakers slang for high elasticity. This a dough that holds its shape well.
Long bread fermentation contributes to fully hydrating the gluten particles, this allows them to be softer.
The softer the gluten, the more able it is to retain bigger air bubbles. Which contributes to a even crumb, that’s soft when touched.
A poorly fermented dough can have a dull, irregular crumb structure that is much less appealing in flavour, looks and keeping quality.
What’s the difference between rest time and fermentation time?
When the dough is left alone to rest and develop, the period is often called fermentation. Correctly, this is a stage of fermentation. But in reality, fermentation occurs as soon as the ingredients come into contact with each other. That means once flour makes contact with yeast, water and salt, the process of fermentation begins, not just when it’s left to do it’s thing naturally.
Bread fermentation includes any time the flour is autolaysed, mixed, rested or proofing. All the stages starting from the first time the ingredients meet, till the heat ends the process in the oven are classed as fermentation.
Any period were the dough is left to ferment naturally is called resting, also the phrase “benching” is used -this refers to place where the dough is typically left to rest.
Bread Fermentation in the bowl
Mixing by hand or mixer typically occurs at the start of a doughs fermentation. Using a pre- ferment, soaker or autolayse are exceptions as they’ve already undergone a previous fermentation before being presented to the other ingredients. There’s more on these later.
Let’s focus on kneading first.
Kneading accelerates bread fermentation. Bashing dough against the edge of a bowl or table forces it to develop faster. A good mixer or skilled baker will have a good kneading action that encourages oxygen to enter the dough whilst stretching the gluten sufficiently. This forms a strong crumb structure ready for yeast fermentation to raise it evenly.
Kinetic energy is given when kneading, raising the temperature of the dough. Warming up the dough creates an environment which yeast thrives. The warmth is encouraged even more if hand kneading by the heat emitted from the baker's hands. If you want to delay fermentation, I often cover the dough and chuck it in the fridge for a bit to slow yeast fermentation down a bit. This article shares more on the best hand kneading technique.
No-knead bread fermentation style
These recipes call for a light mix to evenly distribute the ingredients. Then the dough gets left to ferment naturally often with a few stretch and folds -I’ll explain what a stretch and fold schedule is further down in case it’s unfamiliar to you.
These recipes often use cold temperatures and low amounts of levain for slow fermentation. By not kneading the dough, it must ferment naturally over a longer period to reach its full potential.
The resulting bread has a “bouncy” crumb texture, arguably superior to kneaded dough -depending on who you speak to!
The no-knead method is perfect for some bread styles. But knead, knead a lot, knead a little or no knead, the process of fermentation occurs, it’s just works slightly differently.
Why prove bread twice?
So we ferment the dough, it looks good and then we de-gas it before letting it rise again. What's that all about?
Yeah I got confused too, it took a bit of research and “doing it” before I understood why we prove bread twice. The fermentation period is all about developing flavour and structure into the dough. It can last for a few minutes, hours or even days.
Let’s say we follow a typical routine of mixing the dough, allowing to rest for a couple of hours, then divide, before knocking the air out of it, pre-mould, pre-shape, de-gas or whatever you want to call it…
...Then we’ll mould it and allow the dough to final proof, then finally baking.
When we de-gas (we’ll call it that from now), three things happen:
- Gas gets pushed out.
- The dough becomes firmer.
- The dough’s outer surface (will be the crust) gains extra tension.
- Knocking the air out realigns the gluten to make an even crumb.
- The dough is strong so it retains its shape when final proofing.
- The outside membrane forms which gives a quality crust.
P.s. the dough continues to ferment after degassing and uses the same gluten matrix that had been created -this means its better.
Whilst degassing is not a necessary requirement of baking bread, it makes sense to push the air out of the dough before final proving to achieve the benefits it offers unless an irregular crumb found in ciabatta is required.
Stretch and fold
Stretch and fold is a technique that works similarly to degassing. What sets it apart is that it focuses on developing the dough fermentation as opposed to degassing which is solely for the final stage of fermentation.
A Stretch and fold schedule is a routine given to a whole dough batch. The dough is pulled out and folded on four sides, before being left to rest in a container for a period before the action is repeated.
The stretch and folds are given to the dough at regular intervals before dividing into loaf size pieces, degassing, moulding and final proofing.
To complete a stretch and fold
First place the dough on the table. If it’s been kept in a 4 sided container great, if not just picture 4 sides on the dough. Don’t play with the dough, you want it nice and relaxed.
Then take one side with your right hand and stretch it out as far as the dough feels comfortable, using your left hand to hold the rest of the dough on the table.
Then fold it over itself, at roughly the two third point.
Then take the left side of the dough, stretch it out and then fold it over the other edge.
Then repeat with the top side.
And then the bottom.
Then place the dough back to rest- whilst basking in your own glory “How much goodness have I just put into that dough!!”
Why we stretch and fold
Yeast fermentation needs time, warmth and food to develop. By using the stretch and fold technique, the dough receives the following benefits:
- The gluten network is realigned which supports a stronger structure.
- The yeast gains fresh food to feast on.
- The outside edges of the dough gain more strength to support it when rising.
The stretch and fold method increases the intensity of fermentation in a similar way that kneading does. It highlights a point that I made at the start of the article, the quality of fermentation cannot be overlooked, it’s not all about time.
Placing one stretch and fold into a fermentation period will improve the quality of the dough.
Changing bread fermentation technique such as kneading, resting, stretch and folds and adapting the time or repetition rate allowed will give different characteristics to the dough.
This allows us to create different bread styles from the same ingredients.
How long is long enough?
Ahh the question! It’s a hard one,
“Till it’s ready”
is a response I’ve heard before. But I'll try and be a bit more helpful to you! If you’ve been artisan training, you’ll know it’s not great to rush your baking.
How long does dough need to ferment?
For a standard loaf, we would look for a rest fermentation period of around 2 hours, and a final proof of 1 ½ to 2 hours.
If we want a weaker crumb and less flavour which is necessary in a few British loaves then we would reduce the rest time, but the final proof would be about the same.
For a more intense structure with more aroma I would rest the bread for a minimum of 4-6 hours, with a final proof of 2-6 hours, depending on the recipe.
For speciality breads, use a fridge to retard the dough overnight.
Using a fridge to retard bread dough
Dough can be kept in the fridge, often overnight to ferment. It helps all the previous advantages mentioned of long fermentation, and also gives a more intense flavour, aroma and sweeter taste.
The cold temperature slows down the yeast activity, increasing the fermentation time. But it does more than just slow it down.
Different types of starch, broken starch, more complex starch and finally maltose are broken down during cold fermentation. This unlocks different flavours, only available in cold, long fermentation.
As starch is a form of sugar, breaking down more of it in fermentation generates a sweeter, but mature taste. Further depth of flavour comes from more ethanol being created. More on retarded fermentation below.
It’s argued that it’s not just the production of ethanol that enhances the life of bread. The broken down starch that naturally occurs in all flour types (but in increased amounts in low quality brands) gets repaired which helps to extend the life of the bread.
This reinforces the rule I’ve said for years:
“The longer it takes to make a loaf, the longer it will be fresh”
Oh dear, I’ve realised by having sayings, I’m turning into an old man!!….
...Anyway, next up pre-ferments…
Bigas and poolishes
Bakers often ferment a quantity of the flour, water and yeast (a tiny amount) around 12-18 hours before they make the actual mix.
The starters ingredients are lightly mixed, covered and left to ferment. For breads with an irregular crumb, like ciabatta or traditional baguettes a preferment is essential.
Including a biga or poolish in a dough mix gives the final dough many qualities of a longer fermented dough, whilst using a tiny amount of yeast. This is great for extracting the maximum flavour out of the flour.
The dough structure becomes stronger and the fresh flour that’s added combines with the fermented ingredients for a fresh tasting bread.
It’s a popular way of combining the characteristics of a slowly developed dough with a fast made dough and takes less space in a kitchen or bakery.
It’s also possible create a 3 day fermentation process with the use of a preferment. In the first day the biga is made, the second it’s added to the mix and left overnight to ferment whilst the third day is used for its final proof and baking.
This way extracts the fullest amount from the ingredients and is one of my favourite methods to follow.
Here’s an article that explains Poolishes and Bigas in more detail.
How important is temperature in yeast fermentation?
Yeast is more active at warmer temperatures. Depending on the brand it tends to work best at around 26 Celsius, some prefer it cooler.
Above the optimum temperature the yeast cells start to die off, which halts the process of yeast fermentation. If the temperature drops below it’s activity slows down, which is necessary for long fermentation.
We can ferment dough in a cool environment such as a fridge. When we do this the gas and ethanol production slows right down. But flour still breaks down into longer and stronger gluten strands.
The dough is usually removed from the fridge for final proofing. This is important in large breads otherwise the core of the loaf remains cool when the edges of the loaf spring up with oven spring and gelatinise.
The crust hardens before the centre can think about oven spring creating a dense whilst irregular crumb.
Over fermented bread dough
When this happens it’s quite depressing, but does happen now and again. Sometimes, we forget, can’t keep up with production or get caught in a tidal drift at sea whilst our dough is fermenting to find on return, we’re simply too late.
If and when this does happen the dough becomes over fermented and oxidised.
Over fermented dough is too gassy to mould properly. An additional lack of stretch and folds will mean a weak, uneven crumb structure is common. It tends to have a strong whiff of alcohol as extra ethanol gets created.
So much so, the aroma remains in the bread after baking, masking its natural flavour. No, it’s not like beer bread.
Over fermented flour becomes too exposed to oxygen which turns the flavour bitter.
The dough can also refuse to final prove the dough as the yeast ate all the starch it could find and refuses to ferment any further.
Ok. this is not strictly true, but it will take ages… and yes, I mean ages!
What is bulk fermentation and do I need to do it?
When dough is left to ferment we can choose to divide it straight away into our desired weights for each individual bread, or keep the batch together, scaling the dough pieces when pre- shaping.
The first option is a pretty bad idea, I’ll explain why in a sec, the second is called a bulk ferment.
The bigger the size of the dough that’s fermenting the faster the yeast can multiply, the harder they can work and the time it takes to ferment the dough is reduced.
It’s not just the yeast, the different minerals in the ingredients, especially the flour and the salt impart their qualities and minerals into the dough.
A bulk ferment creates a high quality dough but also a larger area for the yeast to feed and multiply. This leads to a faster fermentation, or at least a more intense one.
This is The Mass Effect.
The bigger the mass of dough that’s fermenting, the quicker the fermentation of the mass. It’s necessary to remember this when baking varied batch sizes as if baking to a strict deadline the amount of levain used will need to be adjusted to compensate.
Can I ferment dough without yeast
Yes, you can use another levain such as sourdough, bicarbonate of soda or pate ferment. A sourdough works with natural yeasts in the air and the wheat.
These are incorporated into a mixture of flour and water and change the ph balance of the mixture over time.
Once added to fresh flour it reacts, raising the dough. It often has a long fermentation period and a crispy crust and is extremely popular in bakeries across the modern world right now.
A sourdough starter creates lactic acid. The longer the starter has developed, the stronger the “lactic twang” is imparted into the bread.
A pete ferment is a piece of yesterday's dough incorporated in the mix, passing down it’s depth of flavour and raising properties into the next days mix.
Doing this everyday for a long period, creates a levain that drives flavour and strength into every dough.
A soaker is a mix of flour and water. This is solely flour fermentation. It’s not going to involve any yeast fermentation, but will develop flavour and a stronger gluten structure.
Soakers are used in wholemeal doughs to lighten the breads texture and support a strong gluten matrix.
Can you make good bread without fermentation?
Modern bakers follow the Chorleywood practice of adding ascorbic acid to the mix. It’s usually included in the flour as it’s dormant until combined with water.
When baking with ascorbic acid the dough forms a strong gluten network much earlier, during mixing actually.
This is opposed to traditional fermentation methods we’ve been focusing on up till now. These need a longer mixing time and a period to rest to ferment into bread dough.
Dough made by following the Chorleywood method does not use a dough rest period. It’s already fermented enough after mixing.
So straight after the bowl, it’s divided, then shaped, before rising in a warm prover.
Of course, this rapid baking strategy stops the dough developing flavour or keeping qualities.
These must be added artificial as extra ingredients, sometimes with E numbers, vinegar, dried malt or sourdough powder. That’s why we don’t use it, ever, in an artisan bakery.
How to slow down fermentation in bread baking
Slow fermentation is king for artisan bread quality. I’ve mentioned how using a cooler temperature is useful, but there are many things you can change to slow down the rate of fermentation other than temperature.
Here’s a few ideas I’ve used in the past:
- Use less yeast or levain.
- Add or increase the amount of sugar in the recipe, at levels of over 5%, fermentation rate is radically reduced.
- More salt will slow down yeast activity.
Drier, more stiff doughs develop slower as it’s harder for the natural enzymes to move about in the dough, so add less water.
What happens after fermentation
After fermentation, the dough will be cut and baked. Actually, it continues to ferment in the oven in the shape of oven spring, check this article out if you wish to learn more.
So fermentation is important in bread baking?
It’s a fantastic process and yes, it is necessary in bread baking!
The more fermentation the better for flavoursome artisan bread.