All grains contain peptides that mimic morphine or endogenous opioid substances. This is where I deal with my latest loaf craving. Get your bread-based exorphin fix here.

Friday, August 17, 2012

2 breads of different viscosity

A rainy day at home, perfect time to bake bread.

Today I am thinking about the viscosity of dough (its resistance to flow).  I'm making two breads that are completely different in the way they feel and perform:

Dough #1
The first is a Tartine-style loaf, approximately 90% whole wheat, with 10% hemp.  It is at 80% hydration, with 5% wheat germ and 2% salt.  This is an extremely wet dough.  I've stretched & folded it Q30min for the full 4 hour bulk fermentation, and it just felt so sloppy that I decided this would best be baked in tins.  It simply would not hold its shape.

Reiterate ingredient list, dough #1:

  • 900g ww flour
  • 100g hemp meal
  • 800g water
  • 200g sourdough starter @100% hydration
  • 50g wheat germ
  • 20g salt

Dough #2
The second dough was made to empty a container.  Long ago I had measured out flour for a 20% rye bread, but I used 80% all purpose flour instead of whole wheat by mistake.  This flour has been sitting in a closed bin for some time, and I've been passing it by in favour of whole grain breads.  But when we got back from holidays, someone who doesn't know I bake bread (i.e. who doesn't know I am a bread snob), out of the kindness of her heart, gave us a raisin bread made with white flour.  I wouldn't touch it, but my wife gobbled it up.  She is frankly tired of my whole grain breads.  She likes mushy white breads.  So I figured I'd make a raisin bread for her out of this old AP&rye dough.

Furthermore, I've been refreshing my sourdough a lot recently since I've been home, getting it back into good shape, and there has been a bit of discard.  In addition to the regular 20% of starter for this dough, I've included some discard that I combined with some 8-grain mix.  I wasn't really measuring anything when I added the 8-grain mix to the starter discard.  But what I ended up with was a ball of mixed grains, that looked to be the size of a fist, and overnight became extremely hard.  It looked like cookie dough, but it was as solid as frozen cookie dough.   I weighed the final result and it was 554g; about 200g of that was sourdough starter that would have otherwise been discarded (so 354g of 8-grain mixture was added).

To use this rock hard ball of fermented mixed grain, I put it in the water (originally 70% hydration, but later I increased this to 85%), broke it up by hand, and then put it in the food processor for about 10 minutes.

Reiterate Ingredient list, Dough #2:
  • 800g all purpose flour
  • 200g rye flour
  • 850g water
  • 400g sourdough starter @100% hydration
  • 350g 8-grain mix
  • 20g salt
  • lots of raisins
  • some liquid barley malt

A careful look at this ingredient list suggests that the true hydration is not 85% but rather 67.7% (total flours, including what was in the sourdough and that pulverized 8-grain mix = 1550g, total waters, including what was in the sourdough = 1050g).  That alone could explain why this dough was so stiff -- but I think also that there were a substantial number of gums in the 8grain mix that were released by the long time they spent in the food processor, and they functioned like glue in the dough.  But I could have added another 120g of water to bring it up to a true 80% hydration!

I mixed the dough by hand, but this dough was far too tight to stretch and fold.  I would knead it by hand q30min, during the bulk fermentation period.  This dough would certainly tolerate forming into a free-standing loaf.  I decided to add the raisins during the final roll-up of the dough.  But I only added the raisins to one of the loaves, because just then my wife walked by.  I had painted on some malt, and sprinkled a few raisins and was rolling up the dough. "Oh no, that's too many raisins", she said.  So I decided not to add any to one of the loaves.

The point is, I had 2 doughs, one very sloppy to work with, and the other very tight to work with.  It had me thinking about rheology.

Rheology (study of the flow of matter) 
and Rheometry (measurement of rheological properties of materials)

The study of Rheology is seeing a huge research investment these days, as people are scrambling to learn about the movement of glaciers, which are disappearing at an alarming rate around our greenhouse planet.  It turns out that everything we've learned about glaciers' movement recently has applications to our bread dough; and everything we've learned about bread dough -- since Newton first conceived describing the flow of materials with forces and vectors -- has applications to glaciers.

Besides Newton, a name keeps popping up when you study the viscosity of dough.  Most articles about bread rheology will reference the work of Dr. Arie H. Bloksma, whose mathematical models of dough are still widely in use.  Bloksma was a mathematician and scientist working at the Institute for Cereals, Flour and Bread in Wageningen  the Netherlands.  The Wageningen labs later became the Nutrition and Food Research International devision of TNO (which stands for: "Applied Scientific Research", a very big independent research company).  Bloksma received his doctorate in Amsterdam, did a post-doc in Winnipeg for the Canadian Research Council, and returned to Wageningen where over his career he published about 30 studies (almost one per year), laying much of the foundation for further scientific study into dough rheology.

Bloksma originally worked with machines like TNO's Chopin Alveograph, and later used other tools to measure flour and dough: the Brabender Farinographs, Weisenberg rheogoniometers, etc.; he also developed his own cone and plate rheometers, to help him plot and predict rheological changes in dough.

Although the tools Bloksma used and the scientific trials he conducted allowed him to develop mathematical models of dough's viscosity, many of which are still used in industry, the ultimate goal of finding a rheological constant eluded him -- and it eludes us still. Dobraszczyk, B and Morgenstern, M. (2003). "Review: Rheology and the Breadmaking process" Journal of Cereal Science 38. pp. 229-245 pointed out that "rheological properties [such as 'stress, strain, strain rate, (elastic) modulus and viscosity'] should be independent of size, shape and how they are measured; in other words, they are universal, rather like the speed of light or density of water, which do not depend on how much light or water is being measured or how it is being measured…(but although)…the (many and varied rheological measuring) instruments … have provided a great deal of information on the quality and performance of cereal products… these instruments do not fulfil the requirements of a fundamental rheological test."  In other words, we still don't have a truly objective yardstick that will give accurate quantitative descriptions of the dough's mechanical properties, or that will accurately describe the dough's molecular composition and structure as it changes, nor predict its performance while mixing and baking.   

Simply put: dough undergoes rapid changes in viscosity and rheology during ordinary mixing and baking conditions, and our understanding of rheology is not yet able to accurately model those changes through the dough's entire cycle.  Weipert, D. (1990) "The Benefits of Basic Rheometry in Studying Dough Rheology" Cereal Chem. 67(4). pp 311-317 and others have continued to stress that the right rheological tests must be done for the correct phase of bread dough development, or the data is meaningless and non-predictive.  Often you find research that measures dough at one mass, through one or two deformations, but these measurements are not applicable to other dough amounts or in other deformations in the creation of bread.

Dobraszczyk and Morgenstern suggest that many bakeries that depend on rheological tests and data are not applying the research in a way that truly benefits them.  Bloksma always tried to simplify the many variables in dough, to make his measurements meaningful and specific to the dough phase studied.  However, he recognized early that many of the most profound changes in dough occur in the interfaces between different stages.  See for example: Bloksma, A. (1981) "Effect of Surface Tension in the Gas-Dough Interface on the rheological behaviour of dough."  Cereal Chemistry 58(6) pp 481-6.

I was browsing through all the rheological articles I could access for free that reference Bloksma on the Internet the other day, and found one that really interested me: Haros, M. et al. (2006)  Rheological Behaviour of Whole Wheat Flour. Institute of Agrochemistry and Food Technology, Spain.

I have reported on the possible dangers of phytates in whole grains before and in this article Haros has used a Chopin Mixolab to measure the dough's rheological  features in different phases of development, comparing doughs with different bran size (phytates are found mostly in the bran layers), or when phytases and other enzymes are added -- the idea being to improve mineral bioavailability in whole wheat bread.  To reduce phytates (which bind nutrients), you require small bran size, longer proofing time, higher temperature, the proper enzymes to break them down -- and calcium salts.  Unfortunately, the author's original language is Spanish, and some of the writing is difficult to decipher.  I still don't quite understand what the absorbability of water, or the viscosity in dough has to do with removing phytates -- I don't immediately see the correlation to rheology.  But it seems that everything that helped break down the phytate required time, and sourdough-like conditions.  The smaller bran sizes (<500 μm) allowed increased water absorption, but the dough took longer to develop; adding fungal phytase (in doses of 0, 100 and 200 μL/100g flour) had a dramatic effect on the water absorption, but detracted from the dough's viscosity.  Adding phytase meant there were more free calcium ions, and alpha-amylase was able to use this to lower staling.

But the most interesting line to me was

"During transformation of flour into bread, phytate content decreases as consequence of the activity of native phytase, but usually not to such extent to greatly improve mineral bioavailability in whole wheat products."
The Mushroom Connection
So I wonder where I can get my hands on some natural fungal phytase?  Would any ground-up mushroom work?  Probably, though Maitake mushrooms seem to have it in generous amounts.  Collopy, P (2004) "Characterization of phytase activity from cultivated edible mushrooms and mushroom substrates"  PhD. thesis, Pennsylvania State University.   But only a few mushrooms have been properly studied (Zhu, M. et al. (2011) "Purification and identification of a phytase from fruity bodies of the winter mushroom, Flammulina veluptipes" Afr. J. Biotechnol. 10(77) pp. 17845-52

It would appear that any given phytase works at its own optimal pH, so not every (mushroom originated) phytase is going to work the best for your particular sourdough.  And the enzymes would be denatured in the cooking process, their only role is during the mixing of the dough, to make the nutrients more available for digestion.

The math of these articles (multivariate analysis, multiple regression equations, etc.) is way beyond me, of course.  But I find it interesting that even the mathematicians continue to argue over the properties of dough.  

Bread still eludes genius.

Why bother with Dough Rheology
Why do I care?  I'm not an industrial baker, and never want to be.  For my part, I merely want to predict what I should do if the dough doesn't feel right.  I can add extra water, or extra flour to get to a consistency that I'm familiar with: but I can't necessarily predict what that will do to my sourdough loaves, when there are so many other variables.

What I would like the scientists to come up with some simple household tests which would assist the home baker to get to know his or her dough better.  I am thinking of such tests as the "windowpane test" (which, incidentally, is not a test I have ever found to be very helpful, because my interest is whole grains, and whole wheat, and the typical windowpane test is not always applicable to my dough.  I have previously blogged about how I originally mistakenly thought that the 'windowpane test' referred to the way in which the dough would slide down if you threw it against your window -- which, if you think about it, should give you some valid rheological data about the dough's stickiness, weight and the deformability of its structure).
WW starter mostly floating on the water.
Some starch is going to begin sinking.
Another easy household test of dough is Chad Robertson's suggestion that a sourdough starter is at its peak to leaven a dough if it can float (which some have said they can never achieve; but their breads still rise.  If you think about it, this floating ability is merely suggestive that the yeasts are already producing gas; but this gas might already be escaping in some cases, because of the texture of the flour used -- so again, this test is another one that may be rather useless if the flour hasn't been mixed in such a way to give you a good gluten cell to contain the gas.  I used to think that the weight of the bran in my whole wheat starter was soaking up water and becoming too heavy to accomplish the water test -- Robertson's starter is a different flour blend, at a constant 100% hydration -- but now I can often get my whole wheat starter to float.  Yet I'm not convinced that it is a good test of what my yeast and dough is capable of).  

My dough is mysterious to me and I long to know what's in it, and how to improve it.  Tiny variations -- ingredients, method -- seem to make a lot of difference to the final loaf that is created.  Subtle changes occur in my dough that I am only beginning to notice, let alone appreciate or understand the causes.  There seems to be an infinite number of things to learn, and it all must be learned first, before I can even begin to ask the right questions.  I'm just a rank beginner, and I suspect I always will be, compared to my dough (which seems to know what to do already).

Bread Results
Dough #1, the one with hemp, made in rectangular tins, turned out nice and moist and lovely.  Lots of flavour.  Didn't rise too much in proofing, but continued to rise a bit in the oven, although I wouldn't exactly call it oven spring.  I suspect that the problem with the hole on the side of the loaf is because of the too-close other pan, changing the flow of heat around the rising dough there.

Dough #2, the one with all-purpose flour and rye, with extra fermented mixed grains, plumped up during proofing but had little oven spring.  I find it a bit dry to eat, although it has an acceptable taste.  There are not too many raisins.

Conclusion: if a dough has more viscosity, more resistance to force when kneading or stretching, it will be a much denser dough.  Denser dough will give you a bread with smaller air bubbles in the crumb, and the dough will not rise as much during the oven stage (although this may not effect the rise during the proofing stage, since denser cells may actually be able to keep the gas that the yeast is producing.  Less viscous doughs may see more and faster yeast gas production, but may not have the cell structure to trap the gas, and it may escape through the bread pores prior or even during baking).

Notes to Myself
  • Examine how phytase is isolated from mushrooms. You don't want to go through the laborious process of isolating the enzyme, but if something as simple as drying and pulverizing mushrooms will allow access to the mushroom phytase without destroying it, you ought to try to add some mushroom powder to your bread dough.
  • Try sieving your whole wheat flour and pulverizing the bran chunks ever smaller -- but toss 'em back in once the gluten is developed.!
  • The gums of multigrain mixtures will create a more viscous dough, especially if they are pulverized in a food processor as they were here.  Remember to check your actual hydration when you do this, and do not forget to add the weight of the multigrain to your flour amounts when calculating hydration.
  • Learn the definitions for all the terminology used in rheology:
  • Sweet and Sour 8grain cookies 

    Because my wife suggested that the dough I was playing with looked like cookie dough, I thought I might try to make some sourdough cookies with what would otherwise be a discard.  I took about 400g of sourdough, and added a bunch of 8grain mixture to it, in the same amount of weight. This was moister than the last time I mixed the 8grain mixture with sourdough. I left it to ferment.

     The next morning, I made hamburger-sized patties with it, and tried eating some -- toasting one, frying one with a couple of eggs in butter. I wasn't too impressed with either. Then I squished all the dough back up and measured it: 450g of sourdough/8grain mixture remained. I looked up some cookie recipes and this is what I tried next: 
    • 450g sourdough & 8 grain mixture 
    • 66g vegetable shortening (1/3c) 
    • 77g water (1/3c) 
    • 118g brown sugar (2/3c) 
    • 2g salt (1/2 tsp)
  • This was pulverized and mixed in a food processor.  I shouldn't have pulverized the shortening I guess.  The result was far too wet -- I was going to add a couple of eggs, but it didn't seem appropriate. I needed to add more dry ingredients, so I added more 8grain mix, and brown sugar, by hand, to get a moist cookie-dough texture:
    • 270g 8grain mix (45g= 1/3c; I added six of these, so 2c) 
    • 59g brown sugar (1/3c) 
  • I dropped balls of this dough on a parchment and pressed it down with fingers and fork, baking at 350 degrees F for 14 minutes. On some of them I sprinkled some sesame seeds. A very strange, sweet and sour taste. Edible, but suspicious.  My wife can't get them past her nose, so kids would likely be the same.

     Probably not a crowd pleaser.  Back to the drawing board.  With cookie in hand.

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