Author Topic: Hydration Basics  (Read 2464 times)

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Offline StrayBullet

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Hydration Basics
« on: October 26, 2010, 05:47:31 PM »
Two things got me thinking about this subject, one being that I've seen recipes that call for dousing both sides of the skin with flour before stretching and have seen several examples of this being done by "famous" pizza makers and the second was a conversation I had a few weeks back and they mentioned something about true hydration, that levels like 68-70% that people make are most likely not truly that "wet."  I didn't pursue that line of questioning as I wanted a little more information under my belt before returning to the discussion.

What factors really go into obtaining a true hydration?  Can the mixing/kneading method affect hydration given the amount of flour and water stay the same between differing methods?  Can an autolysee affect the hydration given the same assumption?

If I take 100g of flour and mix 60g of water, isn't the hydration always 60%?  Regardless of the mixing method/time, kneading method/time, etc. the hydration should still be 60%?  I know the amount of bench flour will play a role and most don't measure out, but considering a minimal amount used, wouldn't the hydration be similar across the board?

Mark


Offline Essen1

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Re: Hydration Basics
« Reply #1 on: October 26, 2010, 06:21:10 PM »
Mark,

To achieve 'true" hydration is somewhat tricky. A couple of factors that immediately come to mind, is the evaporation of water, although perhaps minimal, and the residue water left in what ever container you use to weigh/measure out the water.

I always add a gram or so of extra water because of those two factors. Longer kneading times may play a role, too, because longer kneading times elevate the dough temp and consequently play into the evaporation of moisture. In the Tartine Bread book there are a couple of pages dedicated to that exact subject. It's the pages after the Rustic Bread recipe. It's very informative and can also be adopted for pizza dough.

Keep in mind that the absorption rate of certain flours differ and can affect the subsequent 'feel' of the dough, even at a higher hydration of 68-70%. Autolyse, basically, is a procedure, or rest period if you will, used to ensure the proper hydration of the flour and it also aides in forming gluten strands.

Hope that helps a bit.
Mike

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Offline StrayBullet

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Re: Hydration Basics
« Reply #2 on: October 26, 2010, 08:52:00 PM »
It does, thanks Mike :)

I'm messing around with mixing and kneading techniques and since I do a lot of small batches I tend to do so by hand; I'm always worried about over/under kneading and making sure the flour is incorporated as well as possible.  I don't make enough pies weekly to do a lot of tests so it's hard to compare week to week but practice is the best road :)

Offline Pete-zza

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Re: Hydration Basics
« Reply #3 on: October 26, 2010, 09:16:21 PM »
Mark,

Those are all good questions.

I think you might find it helpful to draw a distinction between hydration as a pure number and the actual capacity of flour to absorb water. As you know, the hydration of a dough can be stated as a number that represents the ratio of the weight of water in a recipe to the weight of flour in the recipe. Having such a number makes it easier to discuss dough recipes and the hydration aspects of such recipes. Also, since that number is a baker's percent number, it can be used with baker's percents for other ingredients to scale recipes up or down and to better analyze recipes. Without baker's percents, including the one for hydration, the dough calculating tools at http://www.pizzamaking.com/dough_tools.html would not exist.

Millers and flour marketers also use hydration numbers in relation to the flours that they mill and sell. The main numbers that they use are "rated absorption values" and "operational absorption values". You can read about these numbers and what they mean and how they are used at the thread at http://www.pizzamaking.com/forum/index.php/topic,4646.msg39204.html#msg39204 and at Reply 9 at http://www.pizzamaking.com/forum/index.php/topic,8419.msg72940/topicseen.html#msg72940. Without having some hydration numbers and recommendations from millers and flour marketers for their flours, bakers would not know what amounts of water they should start with when using different flours. In my case, when in doubt about what hydration value to use when using a given flour, I usually start with the rated absorption value and adjust it as needed based on my experience and results using the flour.

But having numbers on hydration, as useful as they may be, doesn't tell us how much water a given flour can actually absorb. Some of the factors involved in the capacity of flour to absorb water are discussed in the article incorporated in the abovereferenced Reply 9, notably the effects of protein, starch, pentosans and enzymes. However, there are other factors that are implicated in the capacity of flour to absorb water. These additional factors include the type and make of mixer used to make dough (e.g., stand mixer, food processor, or bread maker), the types of attachments used with the dough mixers (such as whisk, flat beater and C-hook or spiral hook), the mix speeds and durations, whether the flour is sifted before using, whether a classic Calvel autolyse or other rest periods are used, how the ingredients are sequenced into the dough making process, and environmental factors such as the moisture content of the flour, elevation/altitude, the age of the flour and how it was stored and, in some cases, the humidity that the flour adsorbs or desorbs at the place where the dough is made. The amount of dough that is made can also be a factor in the sense that if a dough batch size is too large or too small for the mixer used, the capacity of the flour to absorb water is compromised. Also, if a dough is made using hand kneading instead of a machine, the way the dough is kneaded and the duration of the knead will also be factors, as will any special kneading steps used, such as stretch and folds, punchdowns, etc. As you noted, using bench flour will also have an effect on the absorption of water by the dough.

Several of our members, notably Chau, have demonstrated an uncanny ability to incorporate a lot of water into just about any flour, far more than the rated absorption values of the flours in question. To show you that it is possible to hydrate a flour at a value close to 100%, see the dough recipe at http://sites.google.com/site/hollosyt/quickrusticciabattapizza. I believe the lowest hydration value I have used was around 36%, for a cracker-style dough. As you can see from these examples, the hydration as a number does not tell us how much water a given flour can actually hold.

Peter


Offline Jet_deck

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Re: Hydration Basics
« Reply #4 on: October 27, 2010, 10:11:21 AM »

....What factors really go into obtaining a true hydration?... 

Mark

Another thing that Peter pointed out to me one time is that the hydration ratio only accounts for the waters' portion in the recipe.  Other liquids, honey, oil, shortning are not accounded for in the HR.  I believe the term he used was total or effective hydration that takes these into account, although this term is not listed as part of a bakers percent recipe.  Another damming theory to throw in the true HR, would be a discussion about the effects of adding certain dry ingrediants such as sugar or salt.  Sugar or salt could change the ability of any certain flours ability to uptake or to not uptake the water.  All good stuff Mark. :)
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Offline Pete-zza

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Re: Hydration Basics
« Reply #5 on: October 27, 2010, 10:45:22 AM »
Another damming theory to throw in the true HR, would be a discussion about the effects of adding certain dry ingredients such as sugar or salt.  Sugar or salt could change the ability of any certain flours ability to uptake or to not uptake the water.

Jet_deck,

Those are good points. Usually, a properly constructed dough formulation will take all ingredients into account, especially hygroscopic substances like salt, sugar and honey, when establishing the proper hydration value. It is when people take an existing dough formulation and decide to add other ingredients without adjusting the hydration value to take into account the fact that the other ingredients also can absorb water that you can get into trouble. For example, adding/substituting other flours, or adding vital wheat gluten or dry milk powder or dried dairy whey to an existing dough formulation, especially in other than very small amounts, will mess up the hydration.

Peter

Offline Jackie Tran

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Re: Hydration Basics
« Reply #6 on: October 27, 2010, 11:26:52 AM »
Aside from everything that has been posted, 2 other minor variables can cause some inaccuracies when calculating hydration ratios.

If mixing by hand, I can have as much as 5%+ residue lost in the bowl, on the hands, and bench.  That residue usually feels wetter to me than the dough so there is moisture lost there that would effect the true HR.

Environmental variables:  I live in a high altitude & arid environment that I'm sure plays a big role in elevating my hydration requirements.   My flour may also be much drier than somene living in a humid climate. 

Use of Starters:  Unless one measures the amount of flour and water used each time, there's no telling what the hydration ratio of the starter is and how it affects the end HR of the dough.   To incorporate the hydration of the starter, I divide the amount in half and then add those amounts to the flour and water amount in the dough respectively and calculate a new HR.

Use of bench flour as Peter already mentioned.   For me I typically only use about 1gm of bench flour per 2-3 doughballs but if one was using more it can definitely lower your HR by 1%.   

Chau

Offline dms

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Re: Hydration Basics
« Reply #7 on: October 30, 2010, 02:18:57 PM »
Peter,

The "Rated hydration" is merely the amount of water it takes to get a flour that behaves a particular way in a farinograph.[1]  For the commercial spec sheet it is roughly how many plain bread doughs are expected to behave, fairly stiff.  It doesn't tell you very much about how much water a flour can actually absorb, nor what the rheological properties will be at a different level of hydration.  Two flours with the same rated absorption can behave very, very differently when hydration is  more than a few percentage points different. 

If you're after a thin, soft, wet dough, you can put a lot more water than the rated absorption into it, even if it's just flour and water.

[1] A farinograph is a special sort of mixer used for testing flour properties.  Among its capabilities is the measurement of the viscosity of dough, basically by measuring the torque required to mix it.  Dough viscosity is measured in Brabender units, which is an arbitrary scale developed by the people who invented the thing.   500 BU is what's used for most commercial bread flour spec sheets.  Flours intended for widely different uses, like pasta, have different values.  Some cake flours can't even reach the 500 BU mark. 

Offline Pete-zza

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Re: Hydration Basics
« Reply #8 on: October 30, 2010, 02:57:26 PM »
dms,

Thank you for your post. My understanding is as you reported. That was why I referenced the article incorporated in Reply 9 at http://www.pizzamaking.com/forum/index.php/topic,8419.msg72940/topicseen.html#msg72940, and why I gave examples of flours that can absorb little or an enormous amount of water that bear no relationship to the rated absorption values (and even operational absorption values) for the flours.

Peter

Offline norma427

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Re: Hydration Basics
« Reply #9 on: October 30, 2010, 03:44:24 PM »
I have been learning more about hydration levels using KASL, since using starters.  Since I did bulk ferment most of my dough using starters, a few times I tried adding water until the dough became sticker than I could use.  I never posted about these test doughs, but have been trying this method a few times.  It seems after bulk fermenting and if you take the dough out of the container and do reball the dough different times (even if it sticks to your hands), then in the end the hydration seems to come down and the dough is manageable. I havenít tested this enough, but will do this in the future.  This was over a timeframe of about 4 hours.

Norma
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