Gluten Up Close
To better see the gluten network at the microscopic level, we washed away the starch granules before looking at the dough under a scanning electron microscope. The resulting image shows an entangled network of gluten strands that resemble a jumble of highway interchanges.
In bread making, gluten is exceedingly important. Think of gluten as the miraculous net that holds bread together; it helps dough rise by trapping gas bubbles during fermentation and gives bread its unique texture. Although bread begins with many of the same ingredients as cookies, pastries, cakes, and even shortbreads, it has a completely different consistency. Gluten makes bread airy and satisfyingly chewy—it’s hard to imagine enjoying a chewy cake or a bread that crumbles like a cookie.
Gluten is formed when two of wheat’s native proteins, glutenin and gliadin, come into contact with water. Adding water to flour starts a cascade of chemical reactions that can eventually lead to gluten development. When hydrated, the glutenin and gliadin proteins almost immediately bind and form gluten. The longer glutenin pieces link up with each other via disulfide bonds to form strong, stretchy units of molecules. These interlinked strands are among the largest protein molecules yet identified. More compact gliadin proteins allow the dough to flow like a fluid, whereas glutenins contribute strength. Proteases (protein-snipping enzymes) begin cutting strands of gluten into smaller pieces that are able to make additional connections. Protease is found in very small amounts in wheat flour; an excess of it would cut gluten strands too much and have the opposite effect on the gluten network.
The chains of proteins become more numerous and elongated as the dough is mixed; they organize into a sort of webbing that has both elasticity (the ability to stretch) and extensibility (the ability to hold a shape). Without this little protein tango, bread would be a very different thing: flatter, crumblier, denser, and less chewy. The network of gluten will continue to develop, gradually becoming stronger and more complex, up until the dough is fully proofed.
To expand during proofing and baking, the dough must be strong enough to retain the gas that’s produced. Gluten makes the dough elastic enough that the bubble walls can expand like a little balloon without tearing up until the point where the bread overproofs. When carbon dioxide exerts more pressure than a proofed dough can withstand, the gluten structure weakens, releasing the gas and deflating the overproofed dough.
Visit our blog to read more about the science of gluten and important considerations to keep in mind when you make bread.