Subject: 5. What is gluten and how is it developed?
What people call gluten is the formation of linkages between glutenin and gliadin. The "development" of dough consists of the formation of these bonds. These proteins have SH groups on them than can be linked into S-S groups. Just letting the sponge sit allows the reaction to proceed which is why the French call this "long kneading" i.e. you do nothing and the gluten is partially, developed. This is why, in a post to Bruce Hudson on sponge type breads I said that dough could be developed mechanically, (by kneading), chemically (by mixtures of oxidants and reductants) or fermentatively. Very few people realize that you can develop dough in all three ways: they learnt kneading was very important and are fixated on it. In fact kneading is absolutely essential only for straight dough breads.
Kneading, develops gluten by stretching out the proteins, & increasing the rate at which, the molecules collide and the reaction occurs. Kneading also forms an ordered cohesive mass. The reaction remains essentially, a chemical reaction. The virtue of kneading is the mass is very uniform and the gluten can be developed very extensively (homogenous and extensive cross-linking) to give very strong loaves - which will rise spectacularly and have good mechanical strength so you can make free form loaves fearlessly. Most straight dough recipes develop all the gluten by kneading.
Many sponge type breads fall into the category where a lot of the development is achieved by fermentation which allows less or in Jeff's case no kneading. Allowing the gluten to develop by fermentation, simply means that you give the dough sufficient time to let the chemical reactions occur spontaneously i.e. the linkages will form slowly over time. The lattice of cross-linked gluten that forms is not necessarily, as strong or as fully developed but this is undoubtedly what Jeff is aiming for: French country bread is characterized by an uneven crumb - by minimizing mechanical mixing he keeps the mass non homogenous. The simple actions of the original mixing, punch downs, shaping etc. also add a dimension of mechanical development. Relying solely on fermentative development means the gluten will not be completely developed, the loaves will be weaker i.e. you might have a hard time making a large free form loaf with it. By combining some fermentative and mechanical development you can dramatically, alter the range of textures of your bread: there is an infinite spectrum of how long you ferment and how long you and how intensely you knead. By controlling these two you produce dramatically, different breads. This is one of the secrets to the whole range of "French" breads. Jeff is at an extreme when he uses no mechanical development at all. Since he seems to make mainly baguettes this is easy to do - you do not need a very strong dough to hold its form in a baguette. I would be interested to know if your no knead doughs allow you to form large free form loaves.
Several dough improvers including the so called natural conditioners like ascorbic acid (Vitamin C, you will see that it is added to nearly all commercial flour) are oxidants that facilitate the reaction. Similarly, the french add fava bean or soy bean flour which has a lipoxygenase which oxidizes flour i.e. takes SH groups and make them S-S i.e. forms linkages and also bleaches the carotenoid pigments for a whiter crumb. These conditioners have a dramatic effect on the rate of the reaction and the extent to which the reaction occurs. I learnt this very dramatically, when I bought my grain mill: Flour that you buy has been aged or brominated (to oxidize the flour which as explained above forms gluten strengthening cross links & bleaches the carotenoid pigments). Freshly milled flour does not have the benefit of these "improving" i.e. gluten strengthening actions. I noticed that my dough would "fall apart" when kneading very very quickly. This was because the flour was not sufficiently oxidized when freshly milled. This was fixed by adding vitamin C and freshly milled soy bean flour (I simply added back oxidants! It is still not as strong as the strongest flour I worked with. No additions will allow you to turn out a decent loaf too - you just need to know how to handle it).
In some commercial, operations the dough is developed by a long list of chemicals (check any supermarket bread label) that are essential oxidants or reductants and thus facilitate the reaction. This combined with a very intensive short 1 min mixing develops the dough completely!
Just as the cross-links can form so can they break down. This is referred to as the dough becoming "slack" - very long fermented doughs become slack because the cross-linking process reverses itself. In addition there are a number of chemicals naturally, present in dough or from breakdown of yeasts that promote the breakdown of the cross-links. This is one of the reasons you cannot hold the dough infinitely long in a fermentation to improve its flavor. In fact the reason why dry yeast should be reconstituted at 104-114 F is because at lower temps the yeast lyse and release glutathione which affects the oxidation reduction reactions and reverses them leading to slack or weak doughs.
-Roland
See also
Sourdough QA | Sourdough FAQs |Darrell Greenwood's Home Page
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