The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Role of soaker and pre-ferment

Seb43's picture
Seb43

Role of soaker and pre-ferment

After experimenting with a few recipes from the BBA, I'm wondering what is the role of preferments (such as the poolish i mostly use) and soaker.  The author frequently mention that they are meant to extract more flavor from the grains, but this seems a bit vague.  Here are some questions I've been asking myself lately and I would love to hear the opinions of more experienced (better educated!) bakers:

1) what type of flavor is extracted by a pre-ferment?  Are the natural microorganisms of the flour contributing to this flavor (thus explaining the use of very small amount of yeast)?

2) Is the goal of a soaker mostly to soften the bran and other "hard" part of grains?  Is it to give more time for the enzyme to produce some simple sugar from starch?  In some way, isn't any pre-ferment also a soaker?  Would it contribute any flavor if used on AP or bread flour?

3) What is the role of the flour that is added directly to the dough?  Wouldn't it make sense to use all the flour either as a soaker or preferment if this is positively contributing to flavor?  Would it be "too much"?

If some recipes call for both (sometime on the same type of flour, such as in the 100% whole wheat bread from BBA), then it suggests that they contribute different flavor profile.

PMcCool's picture
PMcCool

Those are some thoughtful, and thought-provoking, questions, Seb43.

Generally, soakers are used exactly as you posit: to soften the "hard" bits.  Those may be seeds, or whole or coarsely ground or cracked grains.  Without soaking to soften them ahead of time, they would be like birdshot or gravel in the finished loaf; hard enough to crack a tooth.  Again generally, soakers are commonly done with the seeds/grains and water at room temperature.  You may from time to time see that the seeds or grains are boiled, or have boiling water poured over them.  In this case, you may see the term "soaker" replaced with "scald", or the seeds/grains described as "cooked".  Or not.  Note that a soaker would not have any yeast added, natural or commercial, so it is not a preferment; at least not to the extent that matters to the baker.

Preferments, whether biga/poolish/sponge/levain or other term, have a couple of functions.   Back when baker's yeast was in it's infancy and very expensive, it was a way to economize on yeast usage by, in effect, farming one's own yeast from a very small inoculation of the purchased baker's yeast.  A preferment will bring additional flavors to the finished bread, as Reinhart and others point out.  There are a lot of different chemical compounds involved, but the most common categories are probably sugars, acids and esters.  Some of these are the result of chemical reactions that occur from the enzymes already present in the flour and some are the product of various yeasts and bacteria as they metabolize the flour.  There's a third effect of preferments that doesn't get as much publicity but is still important to the baker: the effect on dough texture.  A finished dough that contains some quantity of prefermented dough will usually exhibit greater extensibility, the ability to stretch without snapping back, than a dough made with exactly the same (but not prefermented) ingredients.

The flour added to make the final dough is there because a) the yeasts in the prefermented dough have already consumed much of the available food there and b) a preferment, by definition, is only a portion of the eventual mass of dough that is required for the bread.  To make the whole dough, more flour, and possibly other ingredients, will have to be added.

Paul

Seb43's picture
Seb43

Thanks a lot Paul, your overview is really helping me pull all the pieces together.  Am I correct in stating the following:

1) When coarse flour is used, as much as possible could be put in the soaker, but this is limited by the fact that the soaker must stay wet (typical hydration % well above 100%) and thus some flour needs to be added later to adjust hydration.

2) A pre-ferment should be considered as depleted in sugar (can't sustain fermentation anymore).  For this purpose, other sources of sugar needs to be added when the dough is formed (could be added flour, soaker, or sugar / honey / etc.).

What would be the difference (flavor- or texture-wise) between using a poolish, biga or pâte fermentée?

Is there a rule-of-thumb on how to estimate the amount of sugar needed to raise the final dough?  (if I use more pre-ferment, could I add a few grams of honey for example?)

--Sebastien

PMcCool's picture
PMcCool

Sebastien,

1) Yes, no, and maybe.  It depends on the flour, on the type of bread being made, etc.  From a texture standpoint, I might choose to soak a coarsely-ground flour to make sure that all of the granules had adequate time to absorb as much water as they could.  This would soften them and contribute to a finished bread with a moister crumb, since those particles would not still be trying to absorb water from the surrounding dough.  This would be doubly true if the flour in question is a whole-grain, rather than a light or white, flour.  In that case, I would especially want to give the bran time to absorb water and soften.  Conversely, a formula may call for an extended fermentation time, in which case the coarsely-ground flour may have enough time to hydrate as part of the dough instead of as a separate soaker.   In general, though, you are correct that if a flour requires soaking, as much of it as possible should go into the soaker.  The actual hydration level may vary from one formula to another.

2) Yes, some of the food content of a pre-ferment will have been depleted but not entirely.  And remember that the yeasts and other organisms aren't dependent on sugar from outside sources; rather, they use enzymes to break the starches into sugars, which they then consume.  Consequently, the addition of the remaining flour for the final dough provides ample food to drive the remainder of the fermentation(s) required for the finished bread.  We usually add other sugars (honey, table sugar, various syrups, etc.) because we want a certain level of sweetness in the finished bread, not because the yeasts will eat themselves out of house and home.  That being the case, no, I can't offer a rule of thumb of how much sugar to add when a pre-ferment is used.  A lean French bread would not call for any additional sugar while a Portugese Sweet Bread might call for quite a bit, even though both of them can be made with pre-ferments.

I'm afraid I can't answer your question about the differences in flavor/texture when using a poolish vs. a biga vs. a pate fermentee.  At best, I can point out that a poolish is (almost always) made with commercial yeast.  Likewise a biga, unless it is a biga naturale that is made with wild yeasts.  Pate fermentee, or old dough, is simply dough saved from a previous bake and used to leaven today's bake.  As such, it could be made with either commercial yeast or wild yeasts.  It also contains some salt, which is not found in either the poolish or biga.  To the extent that those differ from each other, there will be differing effects on the flavor and texture of the breads made from them.

Flavor differences are very much in the mouth and nose of the beholder.  My own impressions are that a bread made with a pre-ferment has a richer flavor, in that there are some acids (sourness) and esters (fruity flavors) and other compounds that aren't present in the same bread when it is made without a pre-ferment.  There may even be a greater level of sweetness, depending on the temperatures that were maintained during the pre-ferment.  Reinhart writes about this in the BBA, so I won't try to repeat that here.

I'm not sure that I have perceived any texture differences in the baked bread, but doughs made with a pre-ferment are usually more extensible than those made without.  Similarly, doughs made with pre-ferments have been noted to show a greater strength than their brethern made with the same flour but no pre-ferment.  I don't have enough information to be able to describe the science.  Use the Search tool here and look up rheology.  You'll get some in-depth information on the topic.

Paul

dabrownman's picture
dabrownman

explaination Paul.  Most helpful and enlightening.

I did know that esters are fruity though.  My Granny Ester was nuttier than a fruitcake by all accounts - not just mine.  I am glad to learn that her name fit her so well for most of her 94 years ;-)

On to researching Rheology - a term I've not heard before.

mwilson's picture
mwilson

Here are some articles regarding pre-fermenents.

http://www.bakerconnection.com/artisanbaker/article_04.htm

http://www.sfbi.com/images/pdfs/NewsSp06.pdf

http://www.theartisan.net/Direct_Sponge_and_Biga.htm

You may also wish to read this article about dough strength as it will help complete the puzzle.

http://www.sfbi.com/images/pdfs/NewsF04a.pdf


Michael

 

Seb43's picture
Seb43

First sorry for reviving an old thread, but I wanted to thank both Paul and Michael for their great answers.  The reading list from Michael took me some time to digest, but after a few weeks I was able to experiment with modifying pre-ferment types and ratios in my formulas with big successes!

Sébastien

mwilson's picture
mwilson

Brilliant! I know I posted a lot of technical stuff...! :)

Perhaps you can share some of your results...

Glad to be of help.

Michael