The Fresh Loaf

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Humidity and Hydration

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mjbleck's picture
mjbleck

Humidity and Hydration

I regularly bake 75% hydration baguettes, but with summer coming on, and higher humidity, my doughs are not behaving. I've gone down to 70% and it's still sloppy. How much of an adjustment might I need to make when the humidity starts crawling up?

Yerffej's picture
Yerffej

Keep adjusting in small increments until it works.  Be aware that conditions can and do change from day to day and you will need to rely on your experience to make the proper adjustments.

Jeff

Doc.Dough's picture
Doc.Dough

A five percent reduction in dough hydration is a lot.   You can check to see if it is just humidity by weighing out 500g of flour, spreading it on a half-sheet, and subjecting it to 3 hrs @ 200°F, stirring occasionally (just don't lose any flour in the process of stirring). Let it cool in the oven for an hour, then reweigh it. The weight loss will represent the moisture content of the original flour. Since you don't have a baseline against which to compare, assume that during the winter your flour was at 12% moisture (more or less - though somebody else may have a better number).   So if humidity is your problem, the weight loss will be 60g (the original 12%) plus enough to compensate for the difference between a 75% dough and a 70% dough (another 25-30g).  But you might find that it not just the humidity.

Doc

flournwater's picture
flournwater

I agree with the experimental approach for getting you "into the ball park" with a starting point for trying to identify the possibility that humidity is the culprit, but you don't need to use 500 grams of flour to accomplish the goal.  250 grams is plenty, as long as you make the mathematical adjustments for the weight differences.  But simply making incremental adjustments, as previously suggested, will probably get you just as close to a solution so that would be my recommendation.  Your post causes us to revisit the importance of learning the feel of the dough and not relying religiously on the formula to produce consistent outcomes.  As environmental conditions change, so does the formula.  Regional adjustments are always necessary  -  no formula works world wide or year 'round.

mjbleck's picture
mjbleck

I agree that that much of an adjustment seems extreme. But what else could it be? Ingredients are weighed to the gram, but I know that if it's a sunny hot and humid day I'm in for a struggle.

Chuck's picture
Chuck

I agree that that much of an adjustment seems extreme. But what else could it be?

Humidity soaking into your stored flour! Flour initially has about 14% humidity, and hopefully doesn't absorb an awful lot more water during storage. But if your flour is stored in a humid cupboard (or even a refrigerator that's opened so frequently you sometimes see condensation on surfaces inside) and the flour sack is not sealed inside a plastic bag or container, your flour could be absorbing a great deal of moisture from the air.

That would throw off your ingredients in a couple ways that would contribute to sloppier doughs. First, even though you scale N grams of flour, it's really less than that because more than the usual 14% or so of what you're weighing is water rather than flour. And second, besides the water you measure for the dough, there's a whole bunch of additional water already in the flour, so the dough turns out sloppier than the measurements would suggest.

PeterS's picture
PeterS

due to the increased humidity. My two cents worth is that surface of the dough is not drying out as fast leading to a more damp and flexible surface than what you otherwise would have at lower humidity.

highmtnpam's picture
highmtnpam

You have solved several of my baking questions.  Could you try to answer some more questions?  Assuming I am buying my flour in high, cool, dry climate will it still be at around 14% moisture when I buy it?  If I buy it and then leave it out on the counter, aproximately how much moisture would I lose per week??

Thanks in advance. Pam

Chuck's picture
Chuck

Assuming I am buying my flour in high, cool, dry climate will it still be at around 14% moisture when I buy it?

Well, unfortunately my reply to this one is "I dunno".

In North America, the gluten content of flour is measured with 14% moisture, so I think it's pretty safe to assume the grain that comes in to the mill is "close" to that, and after a little adjustment the flour that leaves the mill is "very close" to that.

But what happens next while the flour sits on the grocery store shelf before you take it home I just dunno. A wild guess would be that in a cool dry climate the flour on the grocery store shelf would actually lose a couple percentage points of moisture. But I have no information one way or the other about that wild guess:-(


Does anybody else have any experience or information about the effect of different flour storage conditions on actual moisture content?

Doc.Dough's picture
Doc.Dough

Let's do the experiment! This may take a couple of days because I want to have enough samples to estimate the accuracy.

Doc.Dough's picture
Doc.Dough

The answer seems to be 10% moisture content for bagged flour (one sample) and oven-dried flour doesn’t absorb moisture from ambient air very rapidly.

The indicated moisture content of store-bought/home stored Pillsbury Bread Flour was 10.0±0.1%.  The uncertainty lies in the losses associated with getting all of the flour back on the scale to be weighed, but with three successive trials of 100g initial weight, I managed to lose only 114mg, 89mg, and 59mg so I am calling the weight loss 100mg due to measurement error.

Experiment: An initial 100.002g of flour was weighed on a milligram scale, spread on a half-sheet pan (total weight of pan and flour = 856g) and baked in a non convection oven at 200°F for 50 min, after which the total weight was 844g.  An additional 10 min did not reduce the weight by an additional 2g.  The flour was then removed from the half-sheet and reweighted on the milligram scale (this is where the transfer loss could be 100mg).  The total flour weight was 89.873g indicating a reduction of 10.129g (accounted as 10.029g of water and 0.100g of lost flour).

The dry flour was placed on the scale and weighed repeatedly over an 18hr period while being exposed to ambient kitchen conditions (approximately 73°F and 80% relative humidity using a Lufft temperature-compensated certified hygrometer), during which it has gained approximately 0.001g/min on a continuing basis (which continues). The exposed surface is approximately 4.9 sq in and the plastic weighing cup is ~2” deep.  The weight gain measurements have not been time tagged with sufficient accuracy to estimate whether the gain is linear or (more likely) a decaying exponential approaching some final value.  But now that I know what to expect I can do it again with a lightweight pan that will eliminate the transfer loss issue and accurately time tag the weight gain measurements, and work with a smaller amount of flour so that the process runs to completion more quickly.

Doc.Dough's picture
Doc.Dough

With an iterated experimental setup the answer doesn't change much.  For this round I used 29.579 g of flour in a little tray that I made from heavy oven foil (which weighed 5.476 g).  The flour was about 1/4" deep (or less) everywhere.  Total initial weight of flour plus carrier was 35.055 g. It was baked at 200°F for 90 min, losing 11.5% of the flour weight. After removal from the oven, the weight immediatly began to rise as it absorbed water from the air, regaining 4% of the 11.5% weight loss in 50 minutes so you are pretty close if you use a one hour time constant for the process when the flour is all exposed to ambient conditions.  I took a few more points then went to bed, continuing this AM for the remainder of the day. After 24 hrs it has regained most of the total water driven off by heating.  There is a 1% total weight loss that could be an effect of the heating, or just a shift in absorbed moisture due to weather or exposure to room air currents.  The units in the chart below are % weight lost relative to the initial measurement vs time in hours after it was removed from the oven. (0.00 is midnight at the end of day 1).

Flour that is in a paper bag clearly gains or loses moisture relatively slowly (the 100g sample I did first still continues to gain weight and is still about 3% shy of regaining all of the moisture driven off in the oven). A larger bag would delay both moisture loss and gain just because of the diffusion delay to get to the flour in the middle of the bag. Unless you have unusually cold or hot storage conditions that are not inside of a temperature controlled living space, the moisture content probably stay reasonably constant all year round.  For flour that is stored in a well sealed metal can or a plastic tub (or even a plastic bag) the gain/loss should be substantially less. And anything you don't use in 6 months or so should probably be thrown out anyway since it is probably breeding weevils or moths.

 

mjbleck's picture
mjbleck

Just thought someone should throw a post up thanking you for the long hours you put in to put together this data. While it does little to solve my quandry, the rehydration numbers on dried flour are very interesting. Thanks for putting in the time and effort!

jcking's picture
jcking

I'm thinking the hot weather is a bigger concern than the humidity. Try some ice water. My 2¢.

Jim

mjbleck's picture
mjbleck

So it's a nice overcast day and my dough is acting fine.

And I'm in Oregon's Willamette Valley, so the humidity change isn't all that great between winter and summer. It rains all winter long, kind of damp. In the summer it just gets a little muggy.

And I tend to rule out temperature too, because I use a preferment that goes in the refrigerator overnight. On a hot day I'll not wait for it to come to room temp before proceeding, effectively leaving me kneeding dough at about 60 degrees.

My dough just hates the sunshine.

PeterS's picture
PeterS

There is quite a bit more moisture in the air at 50% RH and 70-8o+F than there is at 40-50F and 50% RH. If you are heating in the winter time your inside temperature/humidity will favor faster evaporation.

Can you describe in more detail how your dough is misbehaving?



 

mjbleck's picture
mjbleck

My kitchen is built into the side of a hill, a daylight basement, and as such maintains a pretty even temperature year round. No heating or cooling required. The only heating is from the oven and the only cooling is from an exhaust fan.

At 75% it's a wet dough. But on a good day after about 8-10 minutes in a mixer it will clear the sides and bottom of the mixing bowl. On a bad day it will hardly even ball up. If I add additional flour at this point I can achieve a workable dough but the bread is pretty horrible, with tight crumb and soft crust. On a day when the dough is balling up but not clearing the sides or bottom, I've applied some additional techniques like stretch and fold and that French slap the dough on the table move, and I've gotten good loaves, I just don't have the time to put in those extra steps every day.