This is part three in a series of articles about working with finely-ground whole-wheat flour in sourdough bread. So far, we’ve covered the adjustments you need to make when baking with this flour and the differences in dough hydration and behavior. This article goes more in-depth into the enzymes in whole-wheat and why you should use this flour freshly ground for your sourdough baking.

In the sourdough fermentation process, enzymes, wild yeast, and lactic acid bacteria (LAB) all work together, making the dough rise and develop great flavor. The interesting thing is that whole wheat with its bran and germ delivers many more enzymes than white bread flour, enhancing the sourdough process.

As I started baking with Abigail’s Whole-Wheat White Flour, I have found that the dough ferments more quickly than it does with other grain. To get an eight to twelve-hour bulk rise, my bread dough must spend at least eight hours retarded in the fridge, otherwise it is under-processed and not as easy to digest.

Of course, I had no idea why this was happing until I started reading Whole Grain Breads by Peter Reinhart. It was there I found out how the higher number of enzymes in whole grain flour trigger more activity in the fermentation of sourdough bread. Specifically, these enzymes increase the interaction between wild yeast and bacteria during fermentation.

This is the main reason baking with whole wheat (or any whole grain for that matter) is very different than baking with white flour.

ENZYMES, WILD YEAST, AND BACTERIA IN WHOLE WHEAT FLOUR
Proteases break apart protein (gluten) bonds which soften dough, making it easier to handle and shape. As they break down, amino acid flavor improves and crust during baking is enhanced. There are other enzymes, Reinhart explains, that still “attack smaller sugar chains, such as maltase, which breaks down maltose into its constituent units of glucose.”[3]

But enzymes in whole-wheat flour do much more than just speed up the process of fermentation. Reinhart explains that enzymes affect the taste of bread, how it “feels in your mouth,”[1] and its digestibility. The front stage players in sourdough fermentation include wild yeast and lactic acid bacteria (LAB). Both get most of the credit for making the dough rise. However, Reinhart explains, “enzymes are far more subtle and complex than yeast, pre-ferments, and the other ingredients that we associate with fermentation. They not only affect the starches or the proteins, but the extensibility, elasticity, and workability of dough.”[2]

ENZYMES, WILD YEAST, AND BACTERIA IN WHOLE WHEAT FLOUR
Enzymes that break down starch are called amylases, and those that break down protein are proteases. Amylases (or Diastases) break down starches and turn them into food (malt sugar) for wild yeast. This also browns the loaf during baking; (both alpha- and beta-amylases cause reactions that release sugars into the dough that impart new flavors).

Enzymes themselves are specialized proteins that cause biochemical reactions during fermentation and later during digestion. They break down larger nutrient molecules, like fat, carbohydrates, and proteins, making them easier to digest for better nourishment both in our digestive tracts as well as in a sourdough start and later as the bread ferments. This all starts during the autolyse period when liquid, usually water, and flour are mixed together.  “When starch enzymes are activated,” explains Reinhart, “usually as a result of hydration or increased temperature, they free up smaller threads of sugar from the starch so that the sugar can be converted to energy. In the case of flour, the enzymes alpha- and beta-amylase trigger a reaction that releases threads of various chains of sugar into the dough, making all sorts of new flavors and functions possible…

“Without enzymes to break it down, starch remains fairly tasteless to us because its molecules are sufficiently complex as to slide right over our taste buds—too complex for us to be able to taste the various threads of glucose, dextrose, fructose, maltose, lactose, and other sugars that may be part of its intricate fabric.

“… If, in making [bread], we let it rise once, shape it, let it rise again, and then bake it, we get a so-so loaf of bread with a crust that is usually a yellowish gold in color. However, if we make the exact same bread dough and punch it down after the first rise and then let it rise a second time before shaping it, or if we throw a piece of old dough or a pre-ferment, such as a poolish or biga, into it when we first mix it, the color of the crust is completely different, more of a reddish gold.

“This is the result of the release of smaller sugar chains as well as a particular kind of browning, the Maillard reaction, in which proteins and sugars, affected by various enzymes, brown up in a different manner than sugars alone.“[4]

With a bit of practice, you will be able to adjust your baking rhythm and make great bread using cold water or the fridge to slow down fermentation. As you do, the enzymes will continue to deepen flavors and improve your final product.

Using whole-wheat flour in sourdough bread baking can be tricky but is worth the deeper flavors, creamier crumb, and crustier loaves. Both hydration and enzymes play a big role in the final product, and I have loved the difference this whole-wheat flour makes. We would love to hear about your experience with whole wheat flour in the comment section below.

ENDNOTES

1 Peter Reinhart, Whole Grain Breads, Potter/Ten Speed/Harmony/Rodale (Kindle Edition), 2011.
2–4 ibid.
(Reinhart suggests, “For those wishing to get deeper into this level of cereal chemistry, you can refer to Emily Buehler’s book Bread Science.)