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Cold Fermentation – Why do it?


Dough being proofed in a professional Retardation, or Proofer Cabinet. Unlike domestic fridges these are both temperature and  humidity controlled. In a domestic fridge we need to cover the dough to stop it drying out. A disposable shower cap works very well.


This article looks at cold proofing and cold bulk fermentation and why cold fermentation became popular in Artisan baking, its application in the home baking environment and when not to use it.


Bulk Fermentation and Proofing

Bulk Fermentation: Most home bakers use a period of bulk fermentation which primarily enables the gluten network to be developed. The dough expands, stretching out the coiled gluten molecules into a three dimensional web which traps the CO2 made by the yeasts to give our bread a light and airy structure. We assist the gluten development with kneading, or stretching and folding it over itself. 


Another process which takes place during fermentation is the yeast producing organic acids. Yeast does not produce much in the way of organic acids compared to the lactobacilli in a natural leaven (Sourdough). These acids react with the alcohol, which the yeast also produces, to make bread flavour. These flavour producing reactions are slow and long bulk fermentation times give them the time to develop a better flavoured bread.


The third core process taking place in bread fermentation is enzyme activity. Protease enzymes attack the gluten and cut up the gluten network we are developing. Amylase enzymes break starch down into maltose, the sugar on which the yeast feeds. If too much amylase activity takes place too much starch is degraded and the loaf will not be able to develop the good starch structure it needs to make a light loaf. Freshly milled and wholemeal flours are higher in these enzymes and so people using these need to be a little more vigilant regarding their activity if a light loaf is to be produced. More on this later.


When is bulk fermentation complete? 

As the gluten network develops the gluten becomes more elastic. Those who use stretch and folds at intervals are aware that the gluten becomes more developed and the dough holds its shape better each time they return to give the dough another fold. There comes a point when the gluten is fully developed and it no longer becomes more elastic. If we were to continue to ferment the dough, we would become aware that the dough starts becoming less elastic and more extensible. That is, it does not hold its shape so well. This is because we have taken the gluten past full development and now we are seeing the effects of the protease cutting up the gluten. As the acidity increases, protease becomes more active too. The protease has been cutting up the gluten all of the time, but before this point the gluten network was developing faster than the protease could cut it up. We should really stop the bulk fermentation before this stage as it still has to go through proofing and we really want to have the dough’s gluten at its peak when it goes into the oven. For most of us we don’t have to worry too much about going past peak gluten development, but it comes to the fore with more acidic naturally leavened doughs (Sourdough), because of their higher acidity and when doing long cold fermentation, where the protease has more time for its slow process.


Using mixers and bulk fermentation: The key point here is that mixers develop the gluten network quickly. Artisan bakeries use  a mixer system called Intermediate Mixing. If fully implemented, this fully develops the gluten and reduces the time needed for bulk fermentation to as little as a fifteen minute rest before dividing and shaping. Intermediate mixing typically involves 3-4 minutes on the slowest speed followed by 15 – 20 minutes on speed three (on a typical domestic mixer), though mixing times depend on the flours being used. The advantage of machine mixing for the artisan baker is that a lot of time is saved and time is money.  The price paid with this method is that the time needed to develop good bread flavour is also lost. Because dough development peaks and then begins to deteriorate it is not possible to use full intermediate mixing followed by long fermentation. Too much dough degradation will occur. Some artisan and home bakers do Slow Mixing, where the mixing times are much shorter and slower. Slow mixing for four to six minutes on the slowest speed gets the gluten development off to a good start, but it still allows for long bulk fermentation times.


Proofing the Dough: The dough is still fermenting as we proof it. So the flavour development processes are still taking place. Most of the gluten development takes place in the bulk fermentation stage.

Proofing the dough is mainly about the dough developing its final structure as an inflated, well shaped dough. The flavour continues to develop throughout the proofing stage. Over-proofing takes place when the gluten structure has been weakened both by the over extension of the gluten and too much protease activity. Too much CO2 will have been produced and the weaker gluten no longer has the strength to keep it properly trapped in bubbles. When this occurs tin, or pan loaves, will collapse in the oven as the heated gas expands out of control and freeform loaves will spread too much and they too can collapse.

 

Cold Fermentation – Why do it?

Cold fermentation involves either the bulk fermentation, or the proofing stage, being undertaken in the fridge. The first is called cold bulk fermentation and the second is cold proofing. The general term for both of these processes is Retarding the Dough, as we are slowing down the fermentation with colder temperatures and allowing for more flavour development. Flavour development is a much slower process than fermentation. Yeast more or less stops its fermentation below about 20C 68F, but the flavour development and enzyme activity continues, albeit at a slower pace. 

There are two reasons why a baker might want to do this.

  1. Artisan bakers often want to bake their bread first thing in the morning. This means shorter night shifts and the fridge proofed breads can go straight into the oven in the early morning and be freshly baked in time for the shop opening.


  2. If an artisan baker has used the intermediate mixer method with little bulk fermentation they can use cold proofing to give the dough time to develop good flavours as although the fermentation is slowed down in the fridge, the flavour producing reactions between the organic acids and the alcohol continues.


Cold bulk fermentation is less frequently used in Artisan baking. With machine mixing their doughs are already fully developed. Home bakers on the other hand can use cold bulk fermentation in order to have dough ready to bake over a few days. For example, after 12 – 16 hours  in the fridge, they might remove some dough to make a loaf. The next day they might make some bread rolls from it and on day three they might make some pizzas. Chilled dough can be stretched out much more easily than warm dough. So cold fermentation is a favourite in the home pizza making world.  My experience is that by day four the protease has weakened the dough too much and it will no longer support a loaf. Pitta breads are still a possibility as they do not need a stronger dough to support the very little crumb structure they require. Because the dough is gradually weakening it is often not possible to get a loaf out of the dough beyond 12 – 16 hours cold proofing. On day two I would make rolls which do not have to support the weight of a taller loaf.


Another reason to cold proof a dough is to weaken the gluten so that larger bubbles develop. This is popular with those who like the French, or Tartine style of loaf and who are seeking that classic open French crumb. Firstly the high hydration is used and this weakens the gluten and then the dough is cold proofed to further weaken it and large uneven bubbles are the result.


Ciabatta and Pan de Cristal use high hydration to weaken the gluten and to achieve their large bubbles and open structure.

 

How long to Cold ferment dough

As explained above the dough weakens in the fridge.

Some people do two days cold bulk fermentation, or cold proofing before baking their loaf. These extended times will work with white flours, or doughs, with only a little wholemeal flour in them, as long as the flour is very high in gluten. It’s a case of is there enough gluten in the dough to withstand the gluten degradation and still produce a loaf with a good structure. With weaker flours, such as many of the all purpose flours, extended cold fermentation times can result in dense crumb structure, or the dough collapsing in the oven.

Typically 12 – 18 hours is the recommended period for cold fermentation. However, as above, baking less demanding, flatter, breads with longer periods also works. It is a case of trying it and seeing how your flour and fridge work for you.

 

Yeasted Breads and Natural Leavens (Sourdough)

Yeast produces far less organic acid than a natural leaven. For this reason the long cold fermentation  periods for yeast only doughs will give a big improvement to the bread’s flavour.


Natural leavens on the other hand produce good levels of organic acids so extended cold fermentation is not so necessary. In fact cold fermentation can result in too much organic acid being produced giving a sour sourdough. Also protease is more active when the dough acidity is higher and so there is faster gluten degradation with these acidic doughs. Some people prefer their sourdough breads to be sour. This is more popular in some countries rather than others. Certainly in France and Italy a sour sourdough bread is not welcomed. It is the baker's choice. Personally I want the bread flavours that a natural leaven gives, but I do not want any sourness, so I do not cold ferment my naturally leavened doughs. A long bulk fermentation for four to five hours develops flavour enough. 


When not to cold ferment

There are few things in bread baking which we should never do apart from forgetting to put the salt into the dough. Yes, most of us have done that at least once.

Doughs with higher enzyme levels carry risks with extended cold fermentation. The amylase enzymes break up starches to make sugars. If this process goes too far the bread cannot develop a good starch structure and the loaf will have a dense and gummy crumb.

Protease cuts up the gluten structure and if this goes too far the bread will not be able to trap the CO2 and so it cannot develop a good loaf volume and it will be over dense, or even collapse in the oven.


Wholemeal, or whole grain flours are much higher in enzymes than white flours. My experience is that using up to 10% - 20%  of these with a good white flour will not have too much impact with moderate cold proofing, e.g. 12 - 16 hours.

Freshly milled wholemeal flours are much higher in enzymes as well as being higher in trace elements and other nutrients.


Rye flour is very high in amylase and starch degradation is an ever present danger. Cold proofing should not be undertaken with anything more than 20% of whole rye flour. You will know if the starch has been degraded too much as the bread will be dense and gummy. In Rye baking the term for starch degradation is ‘Starch Attack’. The amylase attacks the starch. 

As with all things bread, bakers sometimes decide to push the envelope to achieve the outcomes they want. It Is always a case of try and see how your flour and fridge perform. This article merely gives some background and guidelines. They are not rules.


Cold Bulk Fermentation versus Cold proofing.

Both allow time for flavour development. Cold bulk fermentation has the advantage that larger amounts of dough can fit into a fridge at one time and the same batch of dough can be used over a few days. The problem with cold bulk fermentation is that the dough has weakened before shaping and proofing has taken place and so the baker is now trying to get a good dough structure from a weakened dough.  With cold proofing the dough attains its size and structure in the earlier stages of cooling in the fridge, when the yeast is still active. Once the dough temperature falls to below 20C 68F the yeast is fairly dormant. So for most of the fridge time it is merely sitting there developing flavour. 

There is a reason why professional bakeries go to the added expense of buying extra refrigeration to enable them to cold proof their dough, rather than buy the lesser amount of refrigeration needed to cold bulk ferment. 


A little more about flavour development

Even with cold fermentation yeast does not produce a large amount of organic acid. The dough will have a much better flavour than it would have had if no cold fermentation had been used. On the other hand Natural Leavens, with their higher levels of organic acids develop more flavour even when cold fermentation is not used. To a degree cold fermentation was introduced in an attempt to improve the flavour of yeast only doughs.


Using the Fridge when baking is interrupted

We live in a busy world and though bread baking is important to home bakers there is always the possibility that something comes up and we have to leave off the bake until we return. Dough can be refrigerated at any stage. 

If we were to be half way through bulk fermentation, give the dough a brief fold and put it in the fridge. Then do a shorter cold bulk fermentation.

If we are halfway through proofing, refrigerate the dough and remove it to complete the proofing when possible. Don’t try to do a full overnight cold proof if the proofing is already well underway. It will over-proof in the fridge. If you have a quick chill setting on your fridge, now is the time to use it. 


If the dough is already in the oven and has had more than 10 minutes to complete the oven spring, just gently take the loaf out and leave it on the side. The dough has baked enough, just, to keep its structure. Try to give it at least twenty minutes in the oven before removing it. Then let it cool on the counter before refrigeration. 


Continue the baking when you return. Using a probe thermometer to measure the internal temperature will tell you when it is baked. 99C 210F for a French style loaf and 94C-96C 201F - 205F for a sandwich loaf. Do not put a partially baked bread into the fridge unless you are following a par baking regime in which case the bread is nearly fully baked before refrigeration. 


How to Cold Bulk Ferment Dough

1  Fully develop your dough using a mixer

OR

2 Knead, or coil fold it until it is no longer shaggy, but smooth and consistent. 

The dough should be between 24C 73F and 28C 82F. If it is too cold it will not be warm enough to ferment in the fridge as it cools. If it is too warm it will ferment too much before it cools.


Place the dough in a container with a lid, or a bowl covered with a shower cap or something similar to stop the dough drying out.


After 30 minutes take it out and give it a quick stretch and fold to even up the dough temperature because the outside will be more chilled.


Leave it for 12 - 16 hours before first using any of it for for baking. 


If you used the hand method, not the mixer, your dough will not have been folded over itself very much. Folding the dough over itself folds the gluten network and that helps it trap the CO2 better. When the cold dough is removed from the fridge make sure to pre-shape it and then rest it for fifteen minutes before shaoping. The extra folds in the pre- shaping will help the gas trapping ability of the gluten. 


Charlie ‘ChainBaker’ has a good video on this.


How to Cold Proof dough

After the dough has been shaped and placed in a brotform, banneton, tin, or pan. Cover it and place it in the fridge. Again disposable shower caps are good for this. 


The dough should be at about 24C 73F and 28C 82F before going into the fridge. 


If you find the dough has not risen enough when you take it out of the fridge, 12 - 18 hours later, it can be left on the side for a short while, say 15 minutes, but this is risky as it is easy to over-proof the dough. Next time try leaving it on the side for up to 15 minutes before putting it in the fridge. Some fridges chill the dough faster than others, so it is a case of learning how your dough and fridge work together.


Cold proofed dough is placed straight into the pre-heated oven from the fridge.


Can you use both together?

There is little point in using both with the same dough. The purpose of the cold fermentation is to ferment in more flavour and for some bakers, to open the dough crumb up giving larger bubbles. In order to use both then both processes would need to be done for a shorter time, or too much gluten degradation would occur.


A caution about yeast dosage

Many recipes use far too much yeast. Using excessive yeast works against slower fermentation. It also makes the dough over-ferment in the fridge.

Standard yeast dosages are

Instant yeast 3g - 5g per 500 kilos of the flour in the recipe. 1 level teaspoon is just over 3g

Active Yeast 4.7g per 500g of the flour weight in the recipe. This is about 2.2 level teaspoons.

Fresh yeast 10g per 500g of the flour in the recipe.


Additional Information 

Increased bread acidity slows bread staling. Cold fermented yeast only doughs and natural leaven doughs stay fresh longer than those which do not use these processes. A naturally leavened bread can stay fresh for up to five days.


Increased acidity reduces the bread's susceptibility to fungus growth. So much so that commercial bakers making their fast “Two hours from flour to into the packet” breads, often add acetic acid (vinegar) to their doughs for this very reason. 


Even with the very best flavour development methods white flour will only ever develop mild flavours. This is because most of the compounds needed for flavour development are in the wheat bran and germ which are removed to make white flour. Substituting a tenth of the white flour, in a recipe, with wholemeal / whole grain flour, or whole rye flour will add a lot of flavour, with no other alterations to the recipe. The bread will no longer be bleach white, but it will still be as soft and voluminous.

 

 

 

 


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Guest
Sep 18

Wow ….fantastic article!

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