Gluten in the Kitchen: Bonus Edition

Gluten in the Kitchen highlighted some of the most common ways we control gluten development in baking. In this bonus post, I’ll cover a couple more that didn’t make it in but are important nonetheless!

Accurately measuring flour

This point is belabored everywhere, but it bears repeating: accurate measurement of all ingredients is crucial to baking success. Baking consists of hundreds of chemical reactions, and for the right reactions to occur, the proportions of the ingredients must be accurate. Flour is especially finicky because it compacts, so when we measure it in cups (as opposed to grams or ounces), it’s easy to pack too much into the cup. Scooping with a cup and pressing against the side of the bag can add up to two tablespoons more flour than spooning into the cup and leveling—that’s a 12.5% difference! Add to that gluten’s role in texture, and we can see why recipe developers stress accurate flour measurement so much.

When we add extra flour, we add more glutenin and gliadin. Baked goods with too much flour are dry because the extra proteins absorb additional water, leaving less water available in the final product to contribute to moistness. The extra proteins also build up the gluten structure, which ultimately lends a dense and tough texture to the final baked good.

If a recipe doesn’t specify how to measure the flour, spoon it into a measuring cup, then level it off with the back of a knife or another straightedge. Even better, use a scale to measure in grams or ounces. Read more about accuracy and precision in measurement here, and take a look at the difference accurate measurement makes in muffins here!

Decreasing protein interactions for less gluten

Mix-ins block gluten.

Mix-ins such as fruits, nuts, or chocolate present physical blockades that prevent gluten strands from extending. Wedding cookies, for example, are shortbread cookies that contain a lot of nuts, and they are crumbly because the nuts keep the gluten strands even shorter than they would be in a typical shortbread. In Bakewise, Shirley Corriher adds water to the flour to develop a little extra gluten before adding it to the other ingredients. (Read more about water in shortbread here!) In most recipes, however, the proportion of mix-ins is low enough that the gluten structure will hold.

Glutathione from milk weakens gluten.

In Gluten in the Kitchen, we identified oxygen and Vitamin C as oxidizing agents that encourage the formation of strong disulfide bonds between gluten strands. I also alluded to compounds called reducing agents, which have the opposite effect. Reducing agents break disulfide bonds in gluten and decrease its overall strength. Bread dough, for example, becomes softer and easier to knead with the addition of reducing agents.

Commercial bakeries often use reducing agents to reduce mixing power, but at home, the most common reducing agent is a tiny string of just three amino acids called glutathione. Because glutathione acts slowly, its activity is mainly pertinent to breadmaking. Milk and dead yeast are a common source of glutathione.

Yeast doughs that contain milk slacken during fermentation due to glutathione activity. The resulting bread rises less in the oven because its gluten cannot trap as much air. To prevent this, some recipe scald milk before adding it to the dough. The heat inactivates the glutathione and prevents it from breaking disulfide bonds and weakening gluten. However, glutathione activity can also be desirable. Breads made with milk instead of water have a more even, fine crumb because glutathione activity decreases gluten strength, which in turn limits air bubble expansion.

Active enzymes break down the gluten network.

Flour, as a product that came from a living organism, contains enzymes. Enzymes are a type of protein that speed up chemical reactions and are involved in processes essential to all life, such as metabolism. (I will cover them in much more depth in a future post!) Like glutenin and gliadin, enzymes from wheat are also preserved in flour and reactivated in water. Flour contains a type of enzyme found in all organisms called proteases, which break down proteins including gluten.

Most commercial flours include some malted flour (you can check the ingredients label for this), which contains a higher level of proteases, as do whole wheat and rye flours. With bread, we take advantage of protease activity when we autolyse (“self-break”) or pre-ferment the dough: flour and water are mixed and allowed to sit for about half an hour, during which proteases break down gluten strands. The resulting dough is more extensible (stretchy).

Proteases typically aren’t active enough to break down too much gluten, but just as with any other enzyme, protease activity can be moderated by a multitude of factors including acidity and temperature. If any one of these variables lies outside of the enzyme’s optimal range, its efficiency will decrease. This is an idea I will explore in more depth in future posts about proteins and enzymes.

References

Bread Illustrated; America’s Test Kitchen: Brookline, 2016.

Buehler, E. Enzymes: The Little Molecules that Bake Bread. Scientific American Blog, 2012.

Corriher, S. O. Bakewise; Scribner: New York, 2008.

Figoni, P. How Baking Works, 3rd ed.; John Wiley & Sons, Inc.: Hoboken, 2011.



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