Sifting bran and how it effects the gluten
I have been milling my own whole wheat flour for my weekly sourdough baking and have been using commercial bread flor as my main flour with around 15% of my home milled unsifted whole wheat flour.
I'm milling with an older lee impact mill.
I have read over and over how the bran weakens the gluten, making for a weaker dough.
I'm not real clear if it's the physical SIZE of the bran particles or the mere presence of the bran from a chemical perspective though.
I want to increase the amount of home milled flour in my bread without making such dense bread like I have gotten using 50% or more of my unsifted whole wheat flour in my recipe.
I went looking for a sieve to sift the flour and see how much bran would come out.
I see lots of reference of people sifting around 15% out to end up with 85% extraction flour from a 40 mesh sieve.
My local restaurant supply only had a couple sieve sizes so I bought the finest one they had to experiment with.
I know that the coin measures 0.95" so counting the squares, I end up at right about 38 mesh for this sieve.
That's real close to a 40 mesh that I often see people getting 15% bran extraction from.
I sieved 453gm of freshly ground hard red wheat flour tonight and I had only 13gm of bran left in the sieve which gets me 97%+ extraction.
I don't think that 38 mesh vs 40 mesh should matter THAT much in how much bran is getting through the sieve but maybe I'm wrong there.
I believe that my impact mill is just breaking the wheat down into much smaller pieces than typical grinder mills that the people who are getting 85% extraction are using.
So, should I get a finer sieve to try to extract more of the smaller bran particles to make a stronger dough when using more of my self ground whole wheat flour or will the small physical particle size of my bran allow me to use more of it without sacrificing dough strength?
This brings me back to my question about the bran particle size vs dough strength.
Is it the chemical presence of the bran or the physical particle size of the bran in the dough making the gluten weaker that gives heavier bread as the whole wheat flour is increased in the recipe?
There are a lot of discussions about softening dry sharp edged bran in whole wheat in the archives. Here is one:
https://www.thefreshloaf.com/node/19402/soaking-bran
My daily bread is similar to yours but it is 20% whole wheat. I mill in Mockmill 100 and use a #40 sieve that takes out roughly 7% of the large brown bits. I can capture more with additional passes through the sieve but mostly just one pass is all I do. It seems to me I get better loft and a more open crumb if the large bran pieces are discarded rather than included in the mix.
Someone here mentioned that the smaller bran pieces do more damage to the gluten network than the larger bits so maybe a finer mesh would help you.
Hi,
Before I jump down one of my rabbit holes, let me start with a disclaimer, which that many scientific studies have come to different conclusions and some of these are contradictory. The biggest take-away (for me,) once you have dug through enough of them is the reinforcement of the concept that baking, despite the seeming simplicity of 'flour, water, salt, yeast' is a complex and entangled beast.
So, that aside, I'll start with . . .
Summary
There are 3 or 4 (depending on how you break it down) factors that I am aware of when if comes to the negative effects of changing from white flour to wholemeal flour.
Assuming a fixed weight of flour and a consistent inclusion percentage of the bran and germ, reducing particle size will only reduce the impact of the physical 'slicing' of the gluten networks. Smaller particles may therefore reduce one negative action, however they may 'take with the other hand' in increasing other negative actions.
Gluten potential
First, the wheat kernel contains the endosperm (~83%), germ (~3%) and the bran (~14%). All of these contain protein, however only the endosperm has protein that will contribute to gluten formation. The simple fact is, therefore, that ANYTHING in the flour that is not the endosperm will reduce the overall gluten formation potential of a given weight of flour. The more 'other' stuff you have - whether it be bran or germ or rice flour or whatever - the greater the dilution of gluten in the dough.
Again, asuming a fixed rate of inclusion, and - e.g. 10% bran/germ - regardless of particle size, this effect in undiminished as the flour will now contain a lower percentage of those proteins that have the potential to form gluten.
Physical disruption ('slicing')
The bran has sharp edges that do indeed physically slice and the gluten network, degrading it.
This property does appear to be affected by particle size so a reduction in mesh size will reduce this negative action.
Competition for hydration
The bran and germ will absorb more liquid than the endosperm. As water is essential for gluten development, the bran and germ will 'compete' for the liquid such that less of it is available for gluten development. This may be partially compensated for by adding more liquid, however that is not a zero-sum game and the added liquid will change the dough in ways that may not be desireable.
Chemical disruption - pentosans
Pentosans are present in all components of the wheat kernel and do actually have a positive effect in that their water-binding ability increases 'shelf-life' by reducing moisture loss.
Importantly, the bran, especially (not sure on the germ) contains a FAR higher proportion of pentosans that the endosperm so any time to include the bran, the percentage of pentosans in the dough increases.
While pentosans do indeed have a positive effect, as above, that is a two-edged sword as the action of absorbing and retaining moisture removes available moisture from the rest of the dough that is needed for gluten development. I am unclear whether this is the only reason why the bran absorbs more liquid than the endosperm, however it is certainly a large factor, even if not the only one. Again, however, you can mitigate this partially by increasing hydration.
On this count, however, it is possible that the smaller the bran particle size the HIGHER the water absorption. Where this has been shown, the suggested action is that the smaller bran particles are a result of an increased level of physical bran damage (being broken up into smaller bits!) and this increase in damage makes those pentosans more available to absorb liquid. Thus, a smaller particle size will actuall be a negative here.
That is an indirect, physical impact of pentosans and my understanding is that it also another indirect but still physical impact due to an increase in viscosity (if you've ever worked with a 100% rye dough this might be familiar!) which 'coats' gluten or at least glutenin/gliadin and prevent correct gluten formation and/or linkages. I am unclear but believe that is somewhat close.
There is also, however, a direct, negative impact on gluten development that has been shown to be a chemical interaction and cannot be overcome - or at least not easily and within the realm of the home baker. In short, pentosans will disrupt - or inhibit - gluten bonds at a chemical level.
This being the case, as with water absorption, the more damage to the bran particle, the more pentosans may be available and thus - potentially - the more this effect will impact gluten quality in the dough.
Wrap-up
(I've already used the word summary!)
In short, and ignoring the germ portion, wheat bran negatively impacts gluten development in multiple ways. One is unaffected by particle size (gluten potention percentage), one may be partially mitigated affected by smaller particle size (physical 'slicing') but two - both of which are related to pentosan content - are likely to be exacerbated by smaller particle sizes.
HOWEVER!!!!
Given you are griding to a certain size and then sifiting the result, that process is neccessarily reducing the percentage of bran in the final product and this will mitigate ALL of the issues. Less bran means more endosperm percentage = more gluten potential, it also means less pentosan percentage and therefore less competition for liquid and less chemical disruption.
This is why I added the caveat near the top that I was assuming - for simplicity - that whatever the particle size, the total percentage of bran inclusion would remain the same.
In your situation, that is obviously not the case, however some - or perhaps most - commercially-available wholemeal flours are not the simple product of the whole kernel being milled in one hit - i.e. a genuine 100% extraction rate. Instead, they are more likely to be pure white flour (endosperm) into which a certain percentage of bran is mixed back in.
My understanding is that the germ is often left out simply because the fats that it contain renders the final product more perishable without adding a great deal of benefit (as it is only 2-3% of the kernel).
What you get in those commercial flours then will be - for argument's sake - a fixed percentage of the bran mirroring the percentage in the whole kernel (i.e. 14-15%) but the particle size will differ from one mill and product to the next.
One more thing that you might like to try to minimise the physical slicing of the bran particles is to first sift VERY fine to obtain something akin to white flour, though this will obviously depend on your grind and the availability of a fine enough sieve!
You will then have a mix of 'left-over' larger and smaller particles that will be mostyl bran/germ. Depending on the desired inclusion rate of the bran in your final flour, you can either sift again to separate out the largest pieces or simply keep it as is. Either way, you would end up with a quantity of mostly 'white' flour and a quantity of bran (of whatever particle size).
What you could then do is make a soaker with the bran portion, soaking overnight in the fridge and then perform a normal 30-60 min autolyse on the 'white' portion and fold the soaker in as you might do with any other inclusion.
The reason I am suggesting this is that longer 'autolyse' times will soften the bran and reduce mechanical damage but will break down gluten due to the action of the enzymes. A short 'autolyse' for the white, gluten-forming portion and a long 'soak' for the non-gluten-forming but rough bran may give the best of both worlds.
Additionally, you can use the opportunity to perform initial development on the white-only dough before adding the soaked bran.
This pre-development of the dough is what I do when adding inclusions like fruit or porridge - first I partially develop the dough - either in a mixer or with slaps and folds and then I fold in the inclusions with the subsequent stretch and fold steps during bulk fermentation. This results in a kind of 'lamination' which, after 3 or so iterations, ends in a fairly homogenous dough.
No reason that wouldn't work perfectly well with the soaked bran as it won't benefit from the initial, more vigorous development anyway.
Just a though.
Dan-
Thanks for the thorough explanation.
I think this gives me some guidance on where to continue my experiments. I will get some finer sieves and start keeping the bran and germ and see about soaking it and bringing it back in during stretch and folds.
I discarded the bran I sifted the other night and I am building dough today using my usual 15% of wholemeal which i mix into my starter poolish with the main water load before I add the main breadflour load but I substituted 50% of my commercial bread flour with my sifted (97% recovery) wholemeal.
The dough is strong on my first stretch and fold but it's not rising as much I get with twice as much white flour.
I'm pretty sure the activity will pick up as I keep working it. Time will tell.
Please report back - I don't mill my own grain (hard to find here in Sydney even if I did have a mill!) but I did buy some bran especially for the purpose of trying the experiment - just haven't gotten around to it yet!
I order rye and wheat grains from Mick's Nuts 31 Hardgrave Rd, West End 4101.
Thanks Gavin - I'll have a look and keep them in mind.
Having recently finally done what I always wanted to do and put a Kenwood on my bench (some of my fondest memories of home are my mum and her Kenwood) I do note that their grinder attachment is a mere $200, which seems rather a palatable price for milling.
But that's a decision for later - for the moment I have somewhere in the order of 30kg of flour to get through and not enough time to turn it into bread. (Turned 1.5 kg into pizza last weekend but that didn't make a huge dent!)
Cheers,
p.
This is a really useful thread - thanks! I've been milling my own 100% wheat grain loaf with a Mockmill 100 Lino and sifting with 60 mesh to get to a white flour. Will definitely be trying the soaking bran method as it would be great to include everything back in the mix.
Currently baking a loaf and wanting to get a good rise and fairly open crumb. Would be good to hear how others have got on with this method, as I think a lot of home millers end up in this position for at least some of their bakes.