Retarding the dough is the technical term for putting the dough in the fridge to extend the fermentation time. It can be a Bulk Retardation, where the dough undergoes some of the bulk fermentation in the fridge, or a Proofing Retardation, where the dough is chilled for some of its proofing time. Longer fermentation times allow the bread to brew in better flavours, just as with beers and wine.
We refer to yeast, but even with instant yeast there are many different yeast varieties in the packet. They all have slightly different characteristics.
Overall yeast’s activity is close to zero at 5oC and below. As the dough cools in the fridge fermentation continues until all of the dough reaches this temperature. Charlie’s (Chain Baker see the link at the end) method of getting his bulk fermentation dough out of the fridge and doing folds is theoretically best practice as he is equalising the temperature throughout the dough as it cools. However, I am aware that Artisan Bakeries do not do this and their 25kg batches take a lot longer to cool than our small domestic batches. It still works.
For the purpose of this article the fridge is assumed to be 4C - 6C. At 6C the yeast and enzymes are a little more active, but not noticeably so.
This is where the dough is undergoing its first fermentation prior to dividing, shaping and proofing.
My own non-retarding practice is to allow a bulk fermented dough a few hours of fermentation with coil folds and giving it a final hour after the last coil fold before dividing and shaping. If I am going to cold bulk ferment the dough, I put it in the fridge immediately after the last coil fold. I generally don’t degas the dough much when I coil fold.
An aside, it’s an old wives’ tale that we need to degas the dough in order to reduce the CO2, because it inhibits fermentation. CO2 is a fairly inert gas and the Yeast is fermenting in its anaerobic cycle. That is, the yeast does not need oxygen. Knocking back the dough does redistribute the gas in the dough a little and this leads to a more even spread of holes (alveoli) in the dough. However, a little gentle patting is enough to do this without loosing so much of that precious gas. The base ball bat degassing method is not recommended.
After the cold bulk fermentation, I give the dough 30min on the worktop to warm up before continuing with the dividing and shaping. So, the dough is well fermented before going into the fridge and it ferments a little more as it warms.
Retarding a dough for proofing
I give the shaped loaf some 15 - 30 minutes on the side either in a banneton, or in the tin (or pan) before placing it in the fridge. I bake straight from the fridge. If the dough has not proofed enough, I would give it some time before putting it in the oven. This has never happened for me. Also, I find the oven spring after a dough has been in the fridge is much greater than the dough volume would suggest. I put this down to the fact that the CO2 making up the bubbles in the dough has a smaller volume because it is cold. Again, this is the practice often used in small bakeries when they retard a dough for proofing.
Cold Retard, or Cold Proof?
The chemistry taking place is the same for both. I choose which to use on the basis of what the end product is going to be and what my time schedule is. If I am not going to be able to get to the proofing stage, because something has come up, then I just pop the dough, covered, in the fridge and come back to it when I can.
For flat breads including pizza I sometimes cold bulk ferment and just tear off some dough as needed over a few days. The rest remains in the fridge. Sometimes I make small boules and put them in those cheap take-away plastic containers stacked in the fridge. They are generally still good to use on day four.
Baguettes are a difficult shape for the fridge, they need a lot of space, I bulk retard baguette dough.
For freeform and tinned loaves proofing in the fridge is my preferred option.
Retardation gives us tremendous flexibility with our baking and it can be used at any stage if necessary, even after the initial mixing. Dough is most tolerant.
Will the dough continue to ferment in the fridge?
Theoretically after the dough has chilled down to 10C 50F, not really. At 5C the yeast has an activity level of some 1% of it's peak fermentation activity at 28C - 30C 82F - 86F
Someone made continuous measurements of the dough temperature, using a remote temperature probe, of their 1.5kg of dough cooling in their fridge. The dough was in two pieces in proofing baskets. And there was nothing else in the fridge. The fridge was a domestic one and it chilled the dough down to 4C, 39F
These were the results:
24C 75F Initial dough temperature
20C 68F The dough is fermenting at 50% of its maximum rate. It took 1 hour to fall this far.
15C 41F The dough is fermenting at 25% of it's maximum rate. It took 2h 45minutes to fall this far.
10C 50F The dough is fermenting at approximately 1% of its maximum rate. It took 4 hours to fall this far.
5C 41F The dough is fermenting at pretty much 0% of it's maximum rate. It took 7 hours to fall this far.
Of course if the dough is placed in the fridge at temperature higher than this tests 24C the chill times will be longer.
At 10C 50F and below for all intents and purposes we can regard fermentation as being halted. Though enzyme activity degrading the gluten will continue all be it at a slower rate.
For this reason cold fermenting is an art. We each need to learn from experience when to put a dough into the fridge allowing for this continued fermentation. I tend to give my dough 15 minutes on the work top before putting it in the fridge to proof for 12- 16 hours. Some people put the proofing basket, or tin, straight into the fridge afer shaping. Your fridge will likely be different.
What if the dough fermented too much?
Just give it a quick coil fold or knead and put it back in the banneton or tin and take it from there. It will proof quite nicely in a warm place. It is inadvisable to do a second cold proofing.
Enzymes appear to be more active than yeast at fridge temperatures. I say this because though the yeast is fairly inactive the dough flavours develop and the gluten deteriorates whilst the dough is in the fridge.
Fermenting dough is far more than producing CO2 to inflate it. Though, sadly, that is all most commercial bakeries do. Increasingly Artisan Bakeries are fermenting less as they try to compete with the big commercial enterprises and their bread type products.
The fact that a retarded dough has more flavour indicates that some chemistry continues in the fridge.
Enzymes can be our friend, or our downfall. One important group are the Protease enzymes. Proteases break protein bonds. When we retard the dough we are giving them plenty of time to ‘chop up’ our carefully developed gluten structure. They literally break some of the bonds joining the gluten molecules to each other. With strong doughs, that is doughs made with strong high glutenin flours, we can afford to lose some of that gluten strength. The dough becomes weakened due to the protease and it takes less effort for the gas to inflate the dough. Thus, we get a higher volume loaf. Their effect is evident when we see the crumb of some of those ‘Artisan’ style loaves with large holes. If we let the process go too far the gluten does not have the strength to hold the CO2 and we then get a denser loaf. For this reason there is a balance between the length of retardation, the increase of flavour and the amount of gluten degradation. Protease action also gives the finished loaf a softer mouthfeel because of the gluten degradation.
High Enzyme flours, aged flours and how long to retard a dough.
All flours contain enzymes. Most flours are aged and the enzyme levels will have decreased. When a flour ages a degree of Glutenin oxidation takes place and the resulting Gluten is stronger and more able to hold the CO2. Glutenin is the precursor of Gluten.
Most of the enzymes are in the Germ and Bran. So is the flavour. White flours are much lower in enzymes than Wholemeal, or Whole Grain flours. Doughs made with strong white flours will tolerate more retardation. Typically a strong white flour dough is retarded for 12-24 hours. Some people retard their doughs for up to three days. That’s fine if the gluten structure will withstand that.
Doughs made with substantial amount of wholemeal flour do not do so well with retardation. The bran disrupts the gluten network weakening it and further weakening may result in it being too weak to give anything other than a heavy loaf. I would certainly be cautious with doughs made with more than 30% wholemeal flours. Having said that I see some ‘supermarket’ flours which have very low levels of enzyme activity. When it comes down to it we are Retarding the dough to get more flavour and wholegrain flours have more flavour anyway. So, one has to ask if retarding a loaf with say 30% or more wholemeal flour is needed in the first place.
In terms of flavour adding 10% wholemeal flour to your otherwise white flour dough is a tremendous flavour enhancer and the loss of soft mouthfeel and loaf volume is minimal.
Freshly milled flours are much higher in enzymes. The best advice is not to retard for long periods, if at all, until you get to know your flours. Freshly milled wholemeal flours are unlikely to tolerate either long periods of autolysis (over thirty minutes) or retardation when used at 50% or more in a loaf.
Rye flour is exceptionally high in amylase in particular. I don’t retard dough with rye fours in them at all. However, for doughs with under 30% rye flour it might be possible. Again, the age of the flour is a factor and no strict rules can be applied.
Amylase is another enzyme family found in flour. They break starches down into sugars. A little is a good thing as this makes sugars available for the yeast. If too much amylase activity takes place the resulting dough is gummy and the bread heavy and not at all pleasant to eat. Again, we can have issues with this and dough retardation as they have more time to work on the starches. This issue seems less prevalent than I would have expected with some aged flours. Increasingly we are seeing millers adding amylase to flour and it really is not necessary for home baking. Bakeries like amylase added to the flour because the dough ferments faster and time is money for them. We generally want slow fermentation because slow fermentation bequeaths more flavour to the finished bread. Flours with added amylase may well be unsuitable for retardation. The bottom line is to read the flour packet to see if it has been added.
Diastatic malt is high in amylase. For this reason doughs containing it are not suitable for retardation. Dried malt and liquid malt do not contain amylase and can be used.
This is a slight aside, but it is worth mentioning here. In some countries bleached flours are still permitted. The flours are bleached at the mill using benzoyl peroxide, chlorine gas, chlorine dioxide, nitrosyl chloride, or nitrogen oxides. Amongst other things bleaching produces Alloxan (2,4,5,6–tetraoxypyrimidine or 2,4,5,6-pyrimidinetetrone). This is implicated in a number of health hazards including Type 1 Diabetes in animals. There are other health issues which have been reported as well. Bleaching was originally introduced in order to get whiter than white loaves. Ageing flour naturally, for six months, has the same effect without the health risks. However, all whitening is caused by the destruction of carotenoids and carotenoids are flavour molecules. We want to keep them. Simply put, bleached flours are best avoided.
Again, this is a slight aside. Making yeasted preferments is another way of extending the fermentation time, at least for some of the flour. There is no reason why a dough cannot have a pre-ferment and a dough retardation.
Preferments can be added to the dough at 15% - 40% of the flours total weight. The total flour weight is the weight of the flour in the preferment added to the remainder of the flour in the recipe. That percentage is the percentage of the flour in the preferment without the water in it. Simply subtract the water used in the preferment from the total water in the recipe. This way a dry Biga ore a high hydration poolish all work out the same for recipe purposes.
Pâte Fermenté is both the easiest and the most flavourful way to make a preferment. For any bake you want a piece of ‘old dough’ with about 15% to 35% of the weight of the dough you are baking. So, if baking with 500g of flour at 70% hydration we want 15% - 35% of that total weight to be old dough. Make up the dough as you ordinarily would, but add the old dough into the dough as an extra. When it comes to dividing the dough remove the same amount of dough that you added and put it into the fridge to be added to the next bake. This is old dough will gradually build up a Lactobacilli (LAB) population, the same as is found in a sourdough preferent. It will take a few weeks and a few bakes for the LABs to become established. Yeast and LABS make more loaf flavour than yeast can on it’s own. It should not make the bread sour. Sour sourdoughs are badly managed sourdough starters in my opinion. Excepting where the baker is deliberately seeking that lactic acid bite. A piece of old dough can also be frozen if you are going away, or want a backup. It will last a year in the freezer quite easily.
A word about Natural Leavens
Natural Leavens a.k.a. Sourdough leavens are the best way to develop flavour. The lactobacilli and the yeast work together to make a fuller flavoured loaf. These doughs can be retarded just as well as a yeast only loaf.
Tip: The fridge is a tremendous way to make a baking schedule fit into whatever other demands are going on. I have made a dough, done the initial kneed and then found I had to leave the house to do other things. I just pop the dough, covered, in the fridge, and continue when I am back. I don't wait until the dough reaches a particular stage. If needed I use the fridge at any point in the bake. An evening bake can be started and continued later, or the next day. It is a pretty handy technique for making bread baking fit into our busy schedules.
Here are some of Charlie Chain Baker's videos on the subject.