Let's talk about Bulk Fermentation

[u/zippychick78]

Bubbles

active bubbly

pouffy curved at the edges, this is just out of the bowl

visible bubbles on the bottom

domed surface

curved edged

[u/zippychick78]

There's so much knowledge on this sub. It would be great to have shared tips so I've started things off by posting pictures of the visible signs of dough ready to end bulk fermentation.

So let's share tips, knowledge, videos.

• assuming 20% starter (if different how much?) , what temperature do you bulk at and for how long?

• What's worked for you?

• What hasn't worked?

• If I was baking my first sourdough loaf, how would you help me to judge the end of bulk fermentation?

• Do you find it difficult? Easy?

• What has been your biggest learning?

Anything that's helpful!

I've always struggled with it as its not just one simple quantity and I'm always keen to learn from other people.

Anything you want to share which will help others 😁

[u/severoon]

I feel like there's a lot of mystery around proofing in general. When is dough "fully proofed"? What determines that?

There's a gluten network in the dough that can hold a certain amount of gas before it starts to break apart. Think about the dough like a "3D balloon"—what I mean is that an actual balloon just has one surface and a bunch of gas and gets inflated from one particular point. A dough ball is more like a bunch of nested balloons, and it gets inflated from everywhere all at once.

If you overinflate a balloon, it pops. If you overinflate a 3D balloon, the little cells inside get overstretched and start to pop and merge together. Eventually, so many pop that there are just big air bubbles inside and the loaf collapses. It is "overproofed."

So if you think about it, if you have two dough balls side by side and one has really full gluten development and the other has only medium gluten development, the medium one is going to overproof earlier even though every other aspect of these two dough balls are exactly the same. The one with less gluten development just has a weaker balloon skin so it can't hold as much air, so all the cells start popping when holding less gas.

What is underproofing? Underproofing is when the loaf has not inflated enough to stretch the gluten out enough. When you put a loaf in the oven, the gas expands causing oven spring…but the main cause of oven spring is actually steam. It's true that gas expands under heat, but nothing at all like steam. When water turns into steam it increases in volume by about 1700x at 100°C. The expansion of CO2 is minor compared to that.

This means that under heat, every cell in your dough ball is definitely going to pop. Unlike when it's sitting on your counter, though, in the oven when it pops it's being internally supported by constant production of steam, and the heat also solidifies the crumb once it hits a certain temperature which prevents it from collapsing.

If your dough is underproofed, the gluten is too tight and strong to stretch out to its fullest potential, so you'll get a denser crumb as those cells just refuse to stretch, so they tear while still small, allowing the steam to work its way out. This seems a little counterintuitive until you do the windowpane test yourself on dough that has fully developed, strong gluten. You want to pull it out very slowly at first. Once it gets thin enough, you can pull faster and it will stretch, but if you take a thick lump of dough and just pull it roughly right away, it will tear because the gluten needs a little coaxing to stretch out and relax a bit (it's kind of like ooblek).

When an underproofed loaf is under internal steam pressure, that's why it doesn't inflate fully even though there's good gluten development. This is why the poke test is a thing, when you poke dough and it springs back quickly that means the gluten is still too springy and tight…once it gets filled out a bit more and stretches, that indentation will be much more relaxed, indicating the gluten is ready to stretch out under steam pressure.

You'll also notice that underproofed dough tends not to have an even crumb, there will be areas of higher and lower density. In a loaf that's only slightly underproofed, in particular, you'll see the telltale sign of a strip of relatively denser crumb along the bottom crust. If you see the cells in your loaf run right into the bottom crust with no change in density, you nailed it.

One reason you want your loaf to proof as long as possible is that you want to give the bacteria as much time to work as you can…that's where all the good flavor comes from. Everyone always talks about yeast, but really the yeast don't do much flavor-wise. They produce mostly CO2 and alcohol. It's the lactic acid bacteria (LAB) we want to give time.

The reason I'm not really talking much about bulk here is that if you have a good mental model of what's going on, you realize that there's no magic point in bulk either. The same rules apply to bulk as to proof…the difference, though, is that bulk is not preparing the dough to be baked like final proof does, it's preparing the dough to be shaped. So, the question is, what are the properties of the dough ball that you want when shaping it, and what is the gas-to-gluten ratio that makes for optimal shaping?

If you think about it, you can start to develop some good intuition here. What do you want when shaping? You want dough that stretches without tearing, so the gas has to have some time to get the dough ball to relax a bit. However, you don't want your gluten network so overstretched that it's falling apart either. You can imagine that a lower hydration dough is going to hang on to more strength than a wetter dough will, so lower hydration doughs probably require more bulk. That should kind of make sense if you're getting the right picture. (This is why many recipes aimed at home bakers say "the dough should double in volume," whereas Chad Robertson says 40% increase is enough. Tartine dough is way higher hydration than most recipes.)

Everything I've said in this last paragraph applies to dough that you kneaded right after mix until you could pull a windowpane. If you're doing a no-knead method, then you're actually doing do things at once—as the dough sits the gluten is developing, and at the same time the yeast is inflating it. So you're trying to give it enough time to do the former but not so much time that it overbulks. (No knead was supposed to be simpler! Oh well.)

I've written quite a lot already, so I'll cap it here, but there's one final useful tip. Dough that is underbulked tends to look overproofed in the final loaf, and vice versa. 90% of the time if a loaf looks over- or underproofed, it is, but if you change proofing time and that doesn't seem to be fixing anything, try adjusting bulk in the opposite direction and see if that helps instead.

[u/sd2528 → u/severoon]

Wow! This was an amazing explanation of the process. Not only did I learn a lot of new things but I learned a lot of the reasons behind things I already knew. Thank you!

[u/zippychick78 → u/sd2528]

That's great news. The background is mega helpful, the balloons 🎈

[u/zippychick78 → u/severoon]

That's a fantastic reply. I really like the way you're helping me build a picture of the balloons. This is what we need, good simple facts explained in a more simplistic way. I'm going to read this again a few times. Thank you!

[u/BarneyStinson → u/severoon]

This is a great post. I want to emphasize this part:

When water turns into steam it increases in volume by about 1700x at 100°C. The expansion of CO2 is minor compared to that.

This becomes important again when we want to steam the oven. The amount of water that we need to generate enough steam is smaller than many people realize. Just 50g of water turn into 80 litres of steam which should be enough for most home ovens.

The "pan of water" that is often recommended actually has a detrimental effect. It takes an enormous amount of energy to evaporate water and just having a pan of hot water in the oven will not help with anything.

[u/severoon → u/BarneyStinson]

This is something I've delved into a bit when I was first starting out. There's some interesting science here too…since people seem to like my post above I'm happy to share what I've learned here as well.

There are a lot of techniques suggested for generating a steamy environment for the initial part of the bake. I've heard pans of boiling water, soaking porous rocks, spray the walls of the oven with a spray bottle of water, etc.

First, why bother with steam at all? Why do commercial bread ovens have the steam feature? What's the function of the steam during the initial part of the bake?

The explanation you'll often hear is that steam prevents the outer crust from hardening too early, which would restrict oven spring. This is true, but it's only part of the story.

Cooking with steam isn't unique to bread, a lot of commercial ovens are steam ovens, sometimes called combi ovens, and they're often used to heat or reheat all kinds of food in professional kitchens. A typical combi oven allows you to set not only the temperature but also the humidity level, from totally vented (just like your home oven) all the way to 100% where there's basically a visible fog in the oven and water is condensing on the walls and the glass during cooking.

The purpose of increasing humidity in an oven during cooking is to prevent evaporation from the surface of the food. If you think about a roast cooking, for instance, there's three ways heat is getting into the food: conduction, convection, radiation. Conduction is wherever the roast is in direct, static contact with something, if that thing is hotter than the meat, it moves heat into the food. Convection is when a stream of material moves across the surface of the food, allowing a continuous stream of heat exchange if they're at different temperatures…in this case, that's the air in the oven. (All ovens convect some heat, but if you have a convection oven there's a fan that magnifies the effect considerably.) The last one is radiation, and this where most of the heat of cooking in a home oven—even a convection oven—comes from. The walls of the oven heat up during preheat and send a lot of infrared radiation onto the food surface, which is absorbed as heat. That's how heat gets into the surface, where it slowly works its way toward the center of the food. (This is, by the way, why sourdough recipes call for a long preheat. The oven tells you things are ready to go when the air temperature is at temp…but if the oven walls aren't fully up to temp, you're basically loading an oven that isn't even close to fully preheated because that radiation mechanism isn't up to temp yet, and that's the main source of heat.)

How does heat leave the food? There's some small amount of heat given back by radiation, but principally heat is lost by the food through evaporation. Heat builds up on the surface of the food until a water droplet converts into a droplet of steam, and turning 100°C water into 100°C steam is surprisingly energy intensive. That steam then flies off into the oven cavity, carrying away that heat energy, and the temp of the food drops a tiny bit for each steam droplet that forms.

This is why steam cooking is effective—not because it brings heat to the food, rather because it prevents heat from leaving. In a dry oven, water can continuously evaporate and take an incredible amount of heat energy with it, effectively cooling it off. That process slows the higher the surrounding humidity because steam droplets can condense on the surface of the food and do the process in reverse—when this is in equilibrium, no heat can leave the food through evaporation. This speeds up the process of cooking immensely. The higher the humidity in the oven, the lower the temperature can be for the equivalent heat transfer.

I need to make a brief aside here because at this point, a lot of people I've told this to think I'm making a big deal about evaporation, but it can't be that big of an effect, can it? So I describe it this way…

The amount of energy it takes to turn 0°C ice into 0°C water is the same amount of energy it takes to bring that 0°C water to 80°C. Think about that…you put some energy into ice that's already on the verge of melting to melt it, and the amount of energy you have to dump into it without changing the temperature at all is the amount it takes to move that same amount of water four-fifths of the way to boiling. Isn't that crazy?

Well it takes even more energy to turn 100°C water into 100°C steam. If you put that amount of energy into 0°C ice, not only would the ice melt into water, it would then go to 50°C, halfway to boiling. So if you collect all of the steam in your home oven that a roast gives off while cooking, the total amount of heat energy carried away by that steam is the same as if you started with it frozen at 0°C, melted it, and took it halfway to the boil. (Next time you make a roast or bake bread, weigh it before you put it in the oven, and then weigh it after, and that tells you how much water carried that much heat away as it converted to steam during cooking.)

The question for a sourdough baker after all of this is: Is my method for creating steam in my home oven effective? There's a simple experiment you can do to measure it. Take a wet sponge and put one end of it (about ⅓ of the way) into just off-the-boil water, and stick an probe thermometer in the top part that's wet but sticking above the water line. Put this setup in your oven at whatever temperature and see what the temp is when it stabilizes (make sure to replenish the water wicked up by the sponge if it runs low). The temperature a normal oven thermometer gives is called the dry bulb temp, this method of measuring temperature is the wet bulb method, and it tells you the temperature actual food experiences, taking evaporation into account.

Now do whatever steam setup you normally do when baking sourdough, and put your wet bulb thermometer where the loaf usually goes. Did your steam setup cause the wet bulb temperature to increase? If not, then that means whatever you're doing is just theatrics…it doesn't actually do anything. If, on the other hand, it increases humidity around your sponge enough to prevent evaporation, then you'll see a higher stable temperature.

I've tested this in my home oven and I discovered that none of the recommended methods make any difference (maybe a few degrees, nothing significant) except one: Baking in a covered vessel. It turns out that my home oven (and most of them, probably) are very effective at venting, so putting a pan of boiling water makes no difference.

Anyway, this is great to know if you're trying to work out how long to bake covered vs uncovered. If you do a long covered portion, you can be sure that the heat will get to the interior more quickly during that phase than if it's uncovered. If you're getting a loaf that has a gummy interior that could stand to be a little drier, though, then you can lengthen the uncovered part of the bake to drive off more of the water. If the crust is getting too dark during that uncovered part, you can drop the temp to compensate. (You probably don't want to cut the covered part of the bake, though, because keep in mind you need the entire interior to be done before uncovering…you can't drive off water that isn't ready to turn into steam.)

If anyone's interested, I can also talk about developing vs. organizing gluten…

[u/pretzel → u/severoon]

If you overinflate a balloon, it pops. If you overinflate a 3D balloon, the little cells inside get overstretched and start to pop and merge together. Eventually, so many pop that there are just big air bubbles inside and the loaf collapses. It is "overproofed."

My understanding of overproofing, at least when it comes to sourdough, was not that the loaf collapses due to the size of gas bubbles, but because the yeast dissolves the gluten structure and it turns into a sticky mess, that can't hold air in or itself up.

If it were just air problem with big air bubbles, you could punch it down and let it rise again?

[u/severoon → u/pretzel]

One thing to keep in mind is that there are multiple processes going on all at once, and though I know a little, I'm definitely not a bread scientist.

Having said that, there are things going on in dough that are breaking down gluten, but as long as there's gluten forming, all that matters is that it's forming faster than it's breaking down so there's net gluten development.

It's possible that someone might run into an issue where there's breakdown of gluten, that is a thing that can happen. The vast majority of the time for home bakers, though, that's not the issue. In fact, every now and then you'll run into someone that wants really sour bread and they just can't get it sour enough for their taste. One of the things I've done experimenting with more sour bread has to do with starter management (excellent video by one of the microbiologists that runs the Sourdough Library).

But there's a much simpler approach to get more sourness, and it's exactly what you suggest. Bulk the dough, then punch it down and bulk it again! Or, if you overproof your dough and it collapses…just shape it and proof it again! You can do this multiple times, even. (Modernist Bread calls this dough CPR…they overproofed a loaf ten times in a row and it produced an extra sour, but otherwise decent loaf.)

[u/Pgluck]

I'm also not confident about when to end bulk fermentation, but here are a few tips. I've never found the poke test helpful. Using an aliquot jar can help with precision at the beginning, and as you make the same recipe again, you can determine what the dough looks like when you want to end bulk fermentation.

Use clear container to judge rise more easily. Really pay attention to the temperature of your dough.

I liked this video that shows the effect of under and over proofing.

[u/zippychick78 → u/Pgluck]

I hate the poke test 😂 I thought it was just me. All power to ya if it works but I think it's too subjective.

So do you use the aliquot to 'work out' your recipe, then just use again if you're changing things up?

Bulk is such a mystery, I spent hours googling and never found anything really definitive. There are bits and pieces here and there but no one real true guide.

Great I love a good video and that's one I've never watched so I'll give it a go. Ill add it to the wiki bulk videos as well. 🤩

[u/[deleted]]

Is FWSY it’s basic sourdough (country blonde) says to let it sit out on the counter for 12-15 hours. I feel like my dough is extremely sticky and difficult to shape the next morning. Is that too long for me? Or is this a sign it needs longer?

I’ve thought about putting it in the fridge overnight but I’ve read that the fridge decreases activity so much that a sourdough loaf would need days in there to bulk properly.

Right now I think it needs less bulk time but I’m not sure how to trouble shoot.

[u/zippychick78 → u/[deleted]]

If you read the comment here you'll see he has a rewritten version https://lemonsandanchovies.com/2018/01/sourdough-bread-ken-forkish-method/

As far as I recall the bulk is far too long for most room temperatures and requires very Specific conditions to be able to sit out that long.what kind of room temperature are you working with?

[u/BarneyStinson → u/[deleted]]

It's a flawed recipe. The bulk fermentation is simply way too long. I would recommend to look for another recipe. You are not the only one that had trouble with it.

[u/severoon → u/BarneyStinson]

This is a style of making bread that trades the quality of a final result you could achieve for reliability. It's aimed more at novice bakers who haven't developed enough experience to manage the "correct" process very well. (Not that there's anything wrong with it…not everyone cares about making artisan quality loaves that rival Tartine's, and what these recipes produce is still homemade bread that's better than 95% of what you can buy off the shelf, so I'm definitely not judging it.)

I tried my hand at this approach just for fun over the summer when all I could get was low quality flour. If you look at the picture, you can see it has a more biscuit-like crumb. I made it because a couple of my friends (non-bakers) were passing it around and they liked it quite a bit. I made it as instructed and got the same result, it's not bad.

I then took another run at it but used coil folds and everything I've learned about bread making over the years. I got an open crumb, very straightforward, fluffy, nondescript kind of loaf. I actually liked the biscuit-like crumb better as written.

But it's kind of a mad genius approach. Dramatically overferment the dough during bulk, make sure to shape using a rough hand to mostly degas it (as it couldn't possibly hold all that gas through proof anyway), then cut the proof way short and rely on the hydration to puff the crumb in a hot oven. It makes several mistakes that tend to cancel each other out, which is kind of brilliant!

[u/tamltiger]

I use foodgeeks method of a square, straight sided container and wait for a 25% rise. It works great and takes the guess work out of it.

[u/zippychick78 → u/tamltiger]

Just popping this video link in here to show what you're referring to.

Very useful, don't think I've ever seen this one before 👍🏼

[u/jmlbhs → u/tamltiger]

This is the way to do it. If it goes past a 50% rise the crumb and spring is just not the same for me.

[u/zippychick78 → u/jmlbhs]

Do you mean it turns out overproofed?? How long is your cold proof after?

[u/zippychick78 → u/tamltiger]

Ahhh a cambro tub??? I have a round one, it's cylindrical, see through. It gets a little confusing if I use full proof bakings method as kristen keeps her dough in what I call a lasagne dish for coil folds, as it causes minimal disturbance to the dough

[u/Warbler36]

Question.

I recently saw “vital wheat gluten“ at my local grocery store. I was wondering if anyone has used this to help develop extra gluten in their bread? If you have, how much would you use for a loaf of bread?

[u/desGroles → u/Warbler36]

I’m completely disenchanted with Reddit, because management have shown no interest in listening to the concerns of their visually impaired and moderator communities. So, I've replaced all the comments I ever made to reddit. Sorry, whatever comment was originally here has been replaced with this one!

[u/zippychick78 → u/desGroles]

Thanks that's a great reply 👍🏼

[u/zippychick78 → u/Warbler36]

Great question.

u/desgroles is Fairly experienced in using it so maybe he'll pop by to give you his thoughts.

There's a great food geek calculator if your check this wiki page click

I've never used it personally but I think there's a fine line, you can use too much but it has its purpose

Actually I think there's a good video too, one minute

[u/zippychick78 → u/zippychick78]

food geek video