Bulk Ferment vs Cold Ferment – Why They Are NOT Interchangeable

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Bulk ferment vs cold ferment: In general, you cannot bulk ferment sourdough in the refrigerator – unless you have a very long time to wait. This blog explains what bulk fermentation is and why it’s ideally not performed in the fridge, as opposed to the cold ferment, which is always done in the fridge.

What Is The Bulk Ferment and How Does It Work?

The bulk ferment or “first rise” as it’s often referred to is where all the magic happens. The yeast in your sourdough starter feed on the food that you’ve given them (the flour and water) and produce C02 gas, which is what rises your bread.

Bulk fermentation should be done at room temperature – so you would leave your dough on the counter for this part of the process. Ideally, sourdough ferments best between 24C – 28C (75F-82F). It will however ferment at a range of temperatures outside of this ideal – the difference is the time it takes.

If the ambient temperature in your home is outside of these parameters – bulk fermentation will still occur, however it may occur at a different rate. For example, if your home is under 20C (68F) then you could leave your dough overnight on the counter for your bulk ferment (as long as you use the correct amount of starter). If your home is above 28C (82F), then bulk fermentation will occur quite quickly.

For tips on making sourdough in hotter or colder temperatures, go here.

At the end of your bulk ferment, your dough will be light and pillowy, full of bubbles and have doubled in size. The surface of your dough will be slightly tacky, but not sticky. There should be bubbles formed underneath which make your dough slightly wobbly to the touch.

How to know when bulk fermentation has finished.
This dough has a domed surface, indicating that it has finished its bulk ferment.

The best advice I can give you in relation to bulk ferment is to watch your dough – not the clock!

Why You Can’t Bulk Ferment in the Refrigerator

One of the most common misconceptions about the bulk ferment is that it can be done in the refrigerator. In general, this is incorrect. We can see from above that bulk fermentation requires a temperature above freezing – but ideally it needs to be above 4 degrees. Anything under this will put your yeast to sleep.

Generally your fridge will be 4 degrees or below – making it way too cold for the yeast to happily work.

The only way you could do the bulk ferment in the refrigerator is if you left it there for a considerable amount of time – like between 3 and 7 days. Yes you read that correctly. Bulk fermenting your dough in the fridge will take a very long time because the yeast are very sleepy at this temperature range. This is why “overnight” bulk fermenting in the fridge never works – it will give you very under fermented dough.

This dough has been underfermented during the bulk ferment vs cold ferment
Under proofed dough will have a tight crumb that surrounds uneven bubbles. It will be dense and gummy.

The other problem with bulk fermenting your dough in the fridge is trying to shape a cold lump of dough. Shaping is much easier when your dough is light and pillowy.

What is The Cold Ferment?

The cold ferment, or cold retard as it’s often referred to, is the part of the sourdough process that occurs after shaping. Once your dough is shaped and sitting happily in it’s shaping container, it can go into the fridge for a rest – or cold ferment.

The cold ferment or cold retard occurs after the bulk ferment and shaping – its not there to further “rise” your bread. It is more to develop flavour, make it easier to score your bread and allow you to put the yeast to sleep so that you can bake the bread at another time. This is why it’s so important to get your bulk ferment right.

Now many people ask why their dough doesn’t rise after being in the fridge for the cold ferment. The simple answer is – it’s not meant to. I believe that some of this confusion has come from people referring to the cold ferment or cold retard as the “second rise” – this is incorrect.

If your fridge is 4 degrees or cooler (as it should be) the yeast will pretty much go to sleep (your bread may rise a teeny bit if you leave it in the fridge for a long time, like more than 24 hours), but in general it’s the bacteria that stay active during the cold retard. The bacteria are responsible for the flavour in your bread, hence why a long cold ferment is a great idea if you like a sour tasting sourdough. The bacteria will produce acetic acid at very low temperatures.

Can You Skip The Cold Ferment

Yes, you can skip the cold ferment. You cannot skip the bulk ferment. If you bulk ferment your dough and then shape it – you do not have to put it in the fridge. You could let it rest while you preheat the oven, score it and then bake it. Of course, our ancestors did not have the luxury of a fridge to cold ferment their dough. As above, cold fermentation lets us control the flavor of the dough, but also allows us to manipulate the process to fit into our busy lives. Skipping the cold ferment may make your sourdough less sour or tangy.

Scoring may not be as easy if your dough is not cold, but if you don’t want anything overly decorative, then scoring dough at room temperature will be absolutely fine.

Using The Freezer to Stop Over Proofing Your Dough

Your bread could also have risen in the first few hours of your cold ferment, while the dough is still cooling down and the yeast are active. This is why it can be tricky to know when to put it in the fridge. If you are sure your bread is heading towards being over fermented as it goes in the fridge for the cold ferment, it could be helpful to pop it in the freezer for an hour or so to really ensure that it drops the temp down and you’re not going to open the fridge to over fermented dough.

If you find that you’re putting nicely fermented dough into the fridge and it’s over-proofing while in the cold ferment stage, it’s really helpful to check the temp of your fridge to rule that out as an issue.

I hope this has helped you to understand bulk ferment vs cold ferment and why they are not interchangeable.

Want all the info you need to bake sourdough in one easy to download book? Check out my e-book “Sourdough Made Easy“.

If you’d like more info on further developing the flavour of your sourdough, this information will be helpful.


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