An introduction to gluten formation:
A water-insoluble protein complex, gluten is comprised of two proteins, glutenin and gliadin. Gluten formation occurs only when water is mixed with wheat flour. Gluten is not present in dry flour alone. When the water is added to the flour, the proteins are wetted. The wetting of the proteins is called hydration. As the proteins become hydrated, they “awaken” from a “frozen” state and become mobile. With this newfound mobility, the two proteins, glutenin and gliadin, are able to interact. The proteins begin to link together through chemical bonds. They link through disulfide bonds, hydrogen bonds and ionic bonds; the disulfide bonds are the strongest of the three.
What exactly is a protein?
From the dictionary: Protein refers to any of a class of nitrogenous organic compounds that consist of large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, collagen, etc., and as enzymes and antibodies.
To simplify this definition further let us look at the different parts it mentions. First, an amino acid is an organic compound that contains both a carboxyl group (–COOH) and an amino group (–NH2). A carboxyl group is simply a grouping of two oxygens, a carbon, and a hydrogen, with a double bond between one of the oxygens and the carbon. An amino group is just a nitrogen with two hydrogens bonded to it. When both groups are present in a structure, it is classified as an amino acid. When amino acids link together and form chains and large molecules, these are called proteins.
What do glutenin and gliadin do?
The two proteins work together to give dough its characteristic physical properties. Glutenin is responsible for strength and elasticity: strength meaning the dough’s tensile strength, i.e. how hard it is to break the dough apart, and elasticity meaning the ability of the dough to revert to its original state after being stretched. The bonds form a tough rubbery substance that provides strength and structure to your baked goods.
Gluten Purists
Gluten is a common name for proteins present in all types of wheat and related grain species. It is even present in barley, rye, and a wheat/rye hybrid called triticale. Kneading your dough is an important aspect of bread making. This is important because for bread we want a lot of gluten development. Gluten bond development is aided by mechanical shear which helps the dough become a viscoelastic matrix that holds the starch granules from the flour. Interestingly enough, these starch granules are able to be washed out of the gluten matrix, and you are able to cultivate pure, unadulterated, gluten.
What do I do with pure gluten?
Pure gluten can be dried into a powder or kept in its goopy, rubbery state. When dried and powdered, the gluten can be added to bread and pasta recipes to enhance the texture and chewiness. Gluten powder also helps batter adhere to foods for frying in both hot and cold temperatures so that your batter does not fall off of your chicken, fries, onion rings, etc, in large clumps. It can even be added to meat products as a binding and enriching agent, often found in sausages.
What affects gluten formation and development?
So many things affect gluten, but I will only mention a few. First, different types of wheat have different amounts of protein. Soft wheat has only 6-8% protein by weight, and its proteins are smaller, so it forms weaker gluten. Hard wheat has more protein ,10-14%, and has larger proteins which form stronger, more elastic, gluten. The difference in protein content is why some recipes call for cake flour or bread flour rather than just all-purpose. Cake flour has 9% protein by weight, all-purpose with 11.7%, and bread flour with 13%. With a lower protein content, cake flour will give you a tender crumb, and with the high 13% protein content, bread flour will yield the most gluten for a hearty, chewy loaf. Hydration is essential for gluten formation, but too much water can be a bad thing. Glutenin and gliadin can both absorb about twice their weight in water, but too much water can dilute the proteins and inhibit their interaction. Salt strengthens gluten by slowing enzyme activity, and fat and emulsifiers work to tenderize the dough by coating the proteins, interfering with the bonds between glutenin and gliadin, and therefore reducing gluten development.
Why does kneading help gluten formation?
Kneading allows more cross-links to form between the proteins. This creates a large network of chemically linked proteins. When you create mechanical shear by kneading, the hydrated proteins are stretched and aligned in the direction of the shear which gives the proteins more opportunities to form these cross-links. As you knead you are also incorporating air which helps to form more disulfide bonds and create protein sheets. Protein sheets are interactions of the large protein structures of gluten with the other large protein structures of gluten to form a large sheet like matrix. This forms a very elastic substance.
Does New York actually have superior water?
Water hardness and pH can also affect gluten formation. Calcium and magnesium in hard water strengthen gluten. This is interesting and plays toward the theory that NYC has better bagels because they have better water. The ideal pH for gluten development is 5-6 and NYC falls perfectly in that range. I’m not saying that NYC has the best water, but it certainly could play a part in their gluten development.
Why are some people gluten intolerant?
Celiac disease makes people gluten intolerant because individuals with celiac disease cannot digest gluten due its inclusion of gliadin. Celiac individuals are not allergic to gluten directly, but rather the inclusion of gliadin in gluten’s structure. Glutenin does not affect those with celiac disease. The inability to digest gliadin damages the small intestine. If an individual with celiac disease were to ingest gluten, the immune system responds by damaging the villi, which are little finger-like projections that line the small intestine. Damaging the villi reduces the body’s ability to absorb nutrients that pass through the small intestine and into the blood stream. This damage is permanent and can lead people with celiac to become malnourished, which is why they must avoid gluten.
Why do I have to let dough “rest”
Flour naturally has enzymes that break down proteins in it. These enzymes are inactive when dry, but when wet, they get to work. Enzymes work to break down gluten into smaller pieces, making the dough softer and more extensible. When you are kneading a dough and you feel it become very tight and hard to knead, let it rest for 10 minutes or so. Often this is called letting the gluten “relax”, but it really is letting the enzymes break down the gluten. In sourdough especially, there is an autolyse stage when you rest the dough for 30 minutes and up to 4 hours. This gives the enzymes time to break down the gluten to produce a more extensible dough, yielding a more open crumb and a bigger volume.
So, after all of this, what is gluten good for?
Gluten is good for the structure of baked goods. To make a chewy, crusty bread, gluten is great. It helps breads to rise and hold their shape by giving the dough better gas retention and elasticity. Gluten gives better absorption and retention of water. This improves the yield of your final good and improves the softness of the product. Gluten also can extend the shelf life of the bread due to the water retention. It is also a flavor enhancer. However, to ensure tenderness, you want to avoid most gluten development. This is why most of my cake recipes say to stir the flour in until “just combined”. Outside of baking, pure gluten can be used in lieu of meat as a vegan option called seitan. Seitan is just vital wheat gluten that is hydrated. It is nutritious and mimics the taste and texture of meat.
Gluten gets a bad rap nowadays, but unless you have a medical condition that makes you gluten intolerant, gluten is not unhealthy. This website gives a good explanation of when to go gluten-free (if you have a medical condition) and when not to (if you’re trying to lose weight or eat “healthier”). The fact of the matter is that gluten is a part of many of our carbohydrates, and cutting these out eliminates some of the key sources of complex carbohydrates needed in a balanced diet. So go out there and enjoy some carbs, and the next time you’re enjoying a lovely piece of chewy, hearty, rustic sourdough bread, be sure to thank gluten.
