Sourdough Bulk Fermentation

Hi HK.  The question is a great one. I’m going to venture a guess.

A dough that produces open crumb is fragile. Imagine a wet, relaxed dough that contains many large gas filled holes (aveoli). The age old advice of “punching down the dough” is painful to even think of with this sourdough. And since we are using sourdough, the fermentation and resulting rise extends over a longer period of time. The longer the flour is hydrated, the more weak and extensible the dough becomes. If the fermentation extends too long the dough will degrade to slop. It is my present thought that if we shorten the BF, we will be able to handle the dough during the pre-shape and shape with much less damage to the aveoli. This way we can anticipate undisturbed gaseous growth during the final stages after all heavy manipulation is complete.

I’m going to reach out to a couple of bakers that excel with this type of crumb. They may reply to this post or straight back to me. If I get any info from them I’ll be sure to pass it on.

The above is not what I know, but what I THINK I know. So I stand to be corrected...

BTW, this question leads me to another.  What exactly takes place during cold fermentation? I placed a new topic concerning this here. http://www.thefreshloaf.com/node/57362/what-exactly-takes-place-during-cold-fermentation

Thanks for bring focus to this issue.

Danny

I'll offer my advice based on my empirical results. I don't have definitive answers to your questions but, much like Dan said, I can really only comment on what I think I know based on many bakes over the years.

First off, I don't usually judge bulk completion based on volume (i.e. 30% rise through bulk). Why? Because I've noticed different doughs rise quite a bit differently. For example, a 100% whole wheat dough @ 100% hydration will likely rise much less than a mostly-white dough with greater gas-trapping capability. Typically I look for other indicators coupled with experience through past bakes to determine when to stop bulk: the smooth look of the dough, the edge where the dough meets the bulk container (I look for doming there, to indicate strength), bubbles on top and at the sides (less so with 100% ww), and I might tug on the dough from time-to-time to assess increased elasticity.

From there, past experience plays a big role. I might try the same same dough several times, all hitting the same final dough temp, and changing the bulk time just a bit each time. When I go to dump my dough out of the container if I see too much activity on the bottom (usually lots and lots of small bubbles) I know I've pushed it a bit too far. Further, if the dough feels weak when I'm preshaping I know next time to cut bulk back a bit (or reduce FDT).

I see the entire fermentation timeline as a continuum -- you start with inoculation and then end with fully proofed dough. If you cut bulk just a bit short (for me this is typically 3.5 hours for my typical white dough) the dough will be stronger with a bit more leeway when preshaping and shaping. The longer you leave the dough in bulk the more gentle you have to be at later stages to, as you guys alluded to, avoid degassing the dough. The later in the continuum at which you divide the more fragile the dough becomes. However, trying to move too early in the timeline will also have consequences -- I've found trying to cut bulk extremely short will lead to dough that never really gets to the same fermentation/taste potential as a properly bulked dough.

Personally I try to push bulk only as far as needed to see that the dough has gained sufficient (I know, all these terms are so nebulous) strength. Once the dough shows plenty of activity, its smooth, has rounded edges, and some elasticity, I divide. I'm very gentle during preshape and further, gentle with the shape. 

I think timing bulk fermentation is the hardest aspect to master with baking. In fact, the two areas where I spend most of my focus trying to improve are dough strength and bulk. Each of these areas presents an opportunity to find just the right balance between each of their extremes: dough that's too slack or too strong, and dough that's been bulked too far or not far enough). For me these areas are challenging but are also what drive my eagerness to bake almost every day.

I hope my experience helps in some way! Happy baking :)

The first thing to understand is that bulk fermentation plays a huge role in how our final bread will end up. The same exact recipe can produce two very different breads depending upon how bulk fermentation was managed. How you approach bulk fermentation will be a major determining factor in the style of bread you produce. 

And "style of bread" is what we need to consider here . . . 

Generally speaking, the 20% to 30% rise in volume is common for the modern Tartine-style breads that are so popular at the moment. As has been mentioned already, a lesser degree of proof makes for a dough that's more tolerant to handling. When you're working with very wet dough -- which already has a low tolerance -- it becomes exceedingly tricky to handle a dough at a high degree of proof without damaging the integrity of the dough. Typically, it starts becoming very difficult around the range of a 50% volume increase. Therefore, the further you let your dough rise during bulk, the greater your dough handling skills need to be. But there's more to it than just that . . .

The amount of rise you attain during bulk has a direct influence on the structure of the dough, and therefore on the style of crumb you achieve. Please note that I use the word "influence" quite deliberately -- what I'm about to discuss are trends and patterns, not laws and guarantees. Dough is extremely dynamic and can be very unpredictable. So with that said . . .

In general, a lesser degree of proof during bulk will tend towards a more irregular crumb while a higher degree of proof will tend towards a more even crumb. I won't get into the why's here because it would take a book to explain (which is why I wrote a book) but not.a.crumb.left covers a bit of it up above. Keep in mind that both irregular crumb and even crumb can be equally open. Whether you prefer even crumb or irregular crumb is a matter of taste, but the typical Tartine-style loaf tends towards an extremely irregular crumb. And this makes sense considering the very wet dough used (which tends towards more irregularity) and the younger bulk that Chad recommends (around 20% rise in volume).

Personally, I usually prefer a minimum of a 30% rise in volume because a 20% rise is near the borderline of too young. It's not too young with the right dough in the right hands, but it can be too young with the wrong dough or in the wrong hands. If you bulk your dough too young then it will not have sufficient structure to hold a good shape. Such loaves tend to flatten out (spread) excessively and may result in a Fool's Crumb type of structure. A 30% rise in volume provides the baker with a bit more room for error while still tending towards a similar crumb. 

So you can see that a 20% to 30% rise in volume during bulk is beneficial for both handling and structural reasons . . . for this style of bread. But what if you wanted a more even crumb pattern? Well, then you may want to extend the rise to around a 50% increase . . . if you have the dough handling skills to manage it, that is. Getting an open even crumb with very wet dough is a real test. 

Now, there are of course many other styles of bread than Tartine-style breads and their hybrids. I often make a loaf I call "Pioneer Sourdough" (named after the once great bakery out in Venice, CA whose sourdough I grew up on). It's a different style completely -- stiff dough, closed and even crumb like a sandwich loaf. It's not "open" in the common usage of the term (large alveoli), but very light and airy -- like a cloud. The texture is not tender and custardy like a Tartine loaf, but soft and fluffy like cotton candy. How does one achieve such a texture without added fats, dough conditioners, sugar, etc.?

It all comes down to how you manage bulk fermentation. We're going well beyond a 30% rise here. You let the dough double in volume, punch it down and degas, then let it double again before once more punching down and turning out for the preshape. So that's a doubling and a doubling in volume. You can do that with a stiff dough -- it becomes very strong and inflated. It can hold a huge volume that way. But don't try this with wet dough unless you enjoy a good sloppy mess. If you were to use the same stiff dough, but only bulk to a 30% increase in volume before preshaping then you will end up with a very different bread indeed. It might still be good -- and potentially more "open" if your fermentation and dough handling are spot on -- but it will be nowhere near as light, airy, or voluminous. Two very different styles of bread from the same exact dough, and all because of how you approach bulk fermentation. Try it for yourself and see.

Hopefully that helps explain why one might recommend a specific rise in volume depending upon what characteristics they are looking for in their bread. Please be aware that volume rise in bulk is not the only way to measure the readiness of a dough. As Maurizio points out, there are plenty of other signs one should pay attention to. But the reason I like to recommend watching the rise in volume is because it's a somewhat more objective measurement to go by. Other signs like bubbles (wetter doughs bubble easier) or doming (stiffer doughs dome earlier) are very dependent upon the qualities of the dough whereas volume rise it a bit easier to be sure of.

Still . . .

As Maurizio also noted, volume rise is also relative to the dough to a certain degree. For instance, a dough that is mixed to full development will immediately start retaining gas and rising whereas a dough that was only partially mixed will lose more fermentation gasses until the gluten is finally fully developed over time. All else being equal, the dough that was fully developed from the start will have a greater increase in volume after a specified time of fermentation than the lesser developed dough.

Now, if you always determine the end of bulk based on reaching the same subjective signs, then your breads will typically possess the same style characteristics (shape, height, volume, crumb structure). And that's perfectly fine if that's how you like it. But if you also add in the dimension of volume rise then you open up a whole new world of characteristics that you can chase after. Yes, your dough may be bubbling and doming nicely, but you note that it's only increased in volume by around 30% and you're looking for a more even crumb structure with this loaf so you decide to let it keep rising past the usual signs until you hit a 50% rise. 

It doesn't need to be one way or the other. I use both subjective signs and "objective" volume rise to determine when my dough is ready. And what I consider "ready" for the loaf I want to make today I may not consider ready for the loaf I want to make tomorrow. 

All of this really just scratches the surface of how the degree of proof we reach during bulk affects our loaves. It doesn't just affect tolerance to handling and crumb structure. It will have an effect on the kind of shape a loaf holds (round, full, flat, sloping, etc.), the height a loaf can achieve, the volume and lightness of a loaf, and even the flavor. So choose your bulk volume rise wisely.

And of course, we haven't even gotten into the effects that folding will have on these characteristics. How often you fold, how you time your folds (close together or far apart), how many folds you perform, how you perform the folds (piggybacking folds, coil folds, letter folds, lamination folds, strong folds, light folds, etc.), and when you perform your folds (folds performed early into bulk will have a different effect than folds performed late into the bulk) all will have a huge impact on the final characteristics of your bread. The better you understand all these variables, the more control you will have over the bread you make. Instead of just following someone else's protocol, or worse -- just guessing -- you can come up with your own procedures that specifically, and intentionally, create whatever kind of bread you want. 

The method makes the bread. 

Cheers!

Trevor