Bread Flour – Rye Flour and Rye Dough

Once you’re on your bread journey apart from being obsessed with the hydration of your dough…one of the questions that will pop up when venturing into different flours is; why can’t you knead rye dough? 

I’ve known the answer for ages because the  How Baking Works book by Paula Figoni has the best and simplest explanations out of my text books on the subject.

Wheat Flour

I’ve mentioned in other posts that wheat flour has two proteins called gliadin and glutenin and these two proteins play a different role.  You may also remember I’ve quoted McGee’s reference to these proteins saying that gliadin and glutenin play a different role in the formation of gluten, these proteins form chains but in different ways.  Gliadin long chains, “…fold onto themselves in a compact mass, and bond only weakly with each other and with the glutenin proteins”.  Glutenins, however, “…bond with each other in several ways to form an extensive, tightly knit network”.  This beautiful relationship between the two is what makes wheat flour great for making bread when the quality and proportions of both proteins is right.

Just as by the way, millers test for the quality and the proportion of the proteins in wheat in order to see what adjustments they have to make and mixes of different flours to get the combination of a good performing flour.  The balance between gliadin & glutenin is important because if the flour has too much glutenin for the amount of gliadin, the dough will holds its shape but doesn’t stretch easily.  If the opposite is true, too little glutenin for the amount of gliadin in the flour, you’ll have a soft extendable dough but it won’t hold its shape well.  Too much protein is referred to as a Bucky dough, too much gliadin a Slack dough.  Can you see how a miller’s job is a balancing act?

What’s Missing In Rye Flour?

OK, back to rye flour…having explained how wheat flour works and the importance of the relationship between its proteins, rye flour doesn’t have the same structure.  Rye flour still has as much protein as wheat but its low in glutenin…glutenin being the chains of protein that bond with each other in different ways tightly giving strength to the the flour.  And since rye is lacking on this department it fails to produce a dough with strength you have in wheat doughs.

According to McGee the glutenin chains in rye flour can’t link up end to end into long chains…I take that to mean from both text books (How Baking Works and Harold McGee) that not only does rye flour have a small amount of glutenin, the glutenin it has can’t form a cohesive chain structure like it does in wheat flour.  That’s your answer in a small nutshell!

What Else Is Different About Rye Flour?

Rye flour is very high in pentosans, 7% of its weight. (Pentosans are a carbohydrate, also known as arabinoxylans).  What pentosans are very good at doing is absorbing water, large amounts of water.  Anyone who has played with rye flour will know this, and this intake of generous amounts of water by the pentosans produces a viscous sticky consitency…the dough becomes like wet cement, that’s what it reminds me of, and for that reason I hate working with it.  Pentosans are so good at absorbing water rye flour will absorb 8 times its weight in comparison to 2 times in wheat flour.

The difference between pentosan carbohydrate and starch carbohydrate is that pentosans don’t harden after being cooked and cooled which is why rye bread stays moist for weeks.  Whatever glutenin rye flour lacks it makes up for it in having pentosans and they provide the dough and bread with some form of structure.

This is what I love about rye bread, this so unpromising cement-like mixture where there’s no skill required from the baker at all, in fact the least the baker does to it the better, will in the end result into a good lasting very flavoursome bread.  One which Northern European countries, my very own birth region in northern Portugal have manage to survive on for centuries, a land otherwise inhospitable to great wheat growing.

Above and below is a stiff rye levain, which has a good appearance of not doing much on the surface but when poking your finger into it you can see activity going on…

The Pentosans and Good Pairing with Sourdough

Pentosans as I’ve mentioned are extremely good at absorbing lots of water and as they swell up they stiffen the dough, enabling it to hold in the gases during fermentation on through to baking.  Pentosans are fragile and plus with the lack of good glutenin it means you should not over-mix nor over-prove rye dough.   

In various text baking books and including in Hamelman’s book will mention how sourdough is a good combination with rye flour and the best explanation I’ve read for this was in the How Baking Works book.  It mentions the use of sourdough in rye flour being good because the acidity in the sourdough will lower the pH of the dough and this lowering action will enable the pentosans to absorb more water and help stiffening the dough which in turn the stiffer dough will help to hold the gases better.


Sourdough and Amylase Activity

The acidity of sourdough has also another benefit and that’s of decreasing amylase activity.  Amylase is an enzyme who’s job is to break down starch into sugars which is what the yeast/bacteria feed on during fermentation.  If you’re like me don’t confuse amylase with amylose..(amylose a component of starch) took a little while to realise the two were different when I was reading text baking books! 

Why is decreasing activity of amylase good for rye dough?  

After all the job of that enzyme to convert starch into sugars is part of the fermentation process so the yeast/bacteria has food to grow…so why is this such a bad thing?  

Well apparently rye flour has more soluble sugars than wheat flours and it means that rye doughs ferment quicker than wheat ones.   This combined with rye’s inability to have a good structure from lack of glutenins the doughs can quickly over-ferment making it collapse.  If the acidity in rye sourdough holds this process back a bit it will help with fermentation, the window is bigger for not ruining your rye dough.

In Geoffrey Hamelman’s book on p46 he details what happens to the dough in the early stages of baking and explains how this enzyme, amylase, is not destroyed until the temperature inside dough reaches 176F / 80C  but in the meantime while the dough is reaching that temperature amylase is in a state of accelerated activity.  Hamelman says once internal dough reaches 122F-140F  / 50C – 60C  the amylase are in, ‘…state of accelerated activity at these temperatures and are not destryoed by heat until about 176F therefore they have an opportunity to wreak considerable havoc by breaking down the starch into sugar and preventing the starch from forming a well structured crumb.  This is the dreaded “starch attack”. The result unless the baker uses his/her skill is the bread with a gummy pasty crumb’.

We want rye bread to be moist but we don’t want it to be gummy and too much conversion of starch into sugar during the early baking stages according to Hamelman can cause this.  He also mentions what How Baking Work book does, that the acidity in sourdough helps to slow this activity.

McGee points out another misfortune of rye grain, “Rye has another major breadmaking liability, it tends to begin sprouting before harvest so its starch digesting enzymes are active during baking and break down the other major source of dough structure.”

As bakers we learn the importance of converting starch into sugar to feed yeast/bacteria is necessary in fermentation but in the case of rye flour which has too much soluble sugars present it can be a bad thing…as they say too much of a good thing is bad for you.

Above: a more liquid rye levain..very active.

Below: on the left wholemeal rye flour, on the right white rye flour.

Sourdough Makes Rye Bread More Digestible

According to one of the text books it says there’s another good thing about the acidity in sourdough, it increases the activity of another enzyme, phytase.  Phytase’s job is to break down phytates which is a compound of phytic acid.  Phytic acid is found in many foods, grains, legumes, seeds, nuts, soya.  From my quick reading up on phytate is that this compound is not digestible to humans and has the ability to make some minerals in those foods unabsorbable, zinc, iron, calcium and magnesium.  The increase activity of phytase breaking down phytate means more of the minerals are released and more readily available in the bread to be absorbed by the body.

This last bit of information about the increased activity of the phytase enzyme was news to me until I started to put information together for this post.  So there you have it, centuries use of sourdough in rye bread is not only benefitting the baker to produce a good tasting bread but it also naturally aids the extraction of more minerals from rye flour.

Proving and Baking

This is about as much information I can store right now and make sense of it.  I will add just a couple more facts.  Rye dough releases most of its gases earlier on in the baking than wheat doughs and for this reason you’ll get a less rise and a denser crumb along with other reasons I’ve already mentioned on here.

My experience with making 100% rye is the following; there’s no point in proving it twice.  Either prove it after mixing in bulk fermentation and then divide and bake straight away, as soon as it’s shaped, which my Gran use to do with her broa bread, (corn & rye loaf) and bakers in Northern Portugal do or do the proving after its in a tin.  The longer you prove it the more gases will be releasing before baking which then will not be aiding the dough to rise in the oven.

I’ll let McGee finish this post for me while I go now and make some much needed coffee, The distinctive complex flavour of rye bread comes largely from the grain itself, which has muschroom potato and green notes (from octenone, methional, nonenal).  The traditional soudough fermentation adds malty vanilla, fried, buttery, sweaty, and vinegar notes.