The Structure of Dough

It's all about water distribution.

It's said water's the stuff of life, and bread, the staff. The first is used to make the second.

Water is essential in transforming a semi-dry powder into a batter or dough. If, as in a classic French bread, a baker adds two-thirds the flour's weight in water, we say the resultant dough is 66.66% hydration. But such a statement is misleading, as flour is only semi-dry; that is, it contains residual amounts of moisture that are nearly impossible to remove, usually below 14% for shelf-stability.

Conversely, most flours contain approximately 86% solids, which means the above-dough has a total hydration of about 94%, or a total moisture content of 48.5%, on a 14% flour moisture basis¹. (Going forward, I'll use “total hydration [%TH]” or “hydration” to refer to any water added by the baker, and “total moisture” or “moisture” to refer to all water present in a system, expressed as a ratio to all solids present.)

As a substance that occupies three-dimensional space, water has long fascinated me.

When I was a young teen hunting with my dad in Texas Hill Country along the Pedernales River, I remember the shallow white-water creeks and inky, deep-slotted pools that miraculously appeared in the worn limestone ravines after an autumn rain. These ephemeral bodies of water sluiced through the smoothed canyons, reflecting the upland oak and juniper stands above. Hopping over rocks, I was awestruck how a barren terrain could transform overnight into a reflecting pool cupped inside the alabaster gullies, cool mint-blue shallows dotted with runty schools of Guadalupe bass.

The landscape gave the water form, a body. If the land tilted even slightly, though, the water ran off to somewhere else. This is water's enigma: it doesn't stay put. Its molecules are never still, even when present in solid material. It flows, to areas of lower concentration (or altitude or pressure), or evaporates.

There's a saying, you cannot stand in the same river twice. You can try. The river might be there, but the water molecules you stood in won't be. They moseyed on downstream, replaced by other water molecules. This adage applies to all bodies of water, solid, liquid or gas. The molecules in a still cup of water aren't still; they only appear to be at our scale of interaction.

The concept of scale lengths will be a central theme in my exploration of bread's many facets. Our understanding of the world comes through observation, and every observation has a time-and-space scale length. There is a tendency in the physical—especially applied—sciences towards reduction, and this is heavily evidenced in food science. If a problem's not easily understood at one level of observation, then it's broken down into smaller units, and the results recorded. Unless such experiments are thoughtfully designed (and they rarely are, in my opinion), the results simply yield more data, not understanding.

The current paradigm in science is informational (i.e., computational). That is, data gathering. The more data, the better. The biological sciences wallow in it, like a pig in mud. We are in the “multi-omics era,” where you take any discipline and whack an -omic onto its tail end, Eeyore-style, to receive funding: epigenomic, exomic, genomic, glycomic, holobiomic, interactomic, lipidomic, metabolomic, proteomic, transciptomic.

The approach uses high-throughput biomolecular sequencing techniques to acquire and process data in order to characterise a system. Such a method is inherently empirical, often problematically so. First, you're only as good as your sample, both in size and quality. Often it's hard to see your sample's limitations. Second, it's exceedingly difficult to draw deeply meaningful conclusions or build fundamental models of the world using statistical input-output procedures. It can amount to fancy census-taking.

Reduction in and of itself isn't bad, when an understanding of the spatiotemporal scale length is contextualised and interrelated within, and to, the entire system being studied. For me, that “system” is bread, starting with the plants and ecosystem that give us the raw, biological starting material and stretching through to the final, baked product we stuff down our pieholes.

This series begins by exploring the structure of dough, which is really about the way water is partitioned in dough and batter systems. While ostensibly simple at a molecular level—it's all just hydrogen bonds that last less than a millisecond—the picture that emerges becomes dizzingly complex as we level up to the macromolecular, supramacromolecular or colloidal, and ultimately macroscopic scales. Understanding how and why water is distributed in a dough or batter sheds light on many topics, from rheology to microbiology, and answers questions such as:

How does hydration affect the quality or rate of fermentation?

Why is the outside of a dough smooth but its inside sticky?

Why is a dough's “optimal,” or maximal, hydration well below the cumulative water-absorption capacity of its principal parts (namely, proteins, starch and pentosans)?

What, exactly, does it mean for a dough to be under-, optimally-, and over-mixed?

Why is it nearly impossible to make a naturally-leavened croissant with normal levels of sugar (<15%) that's not sour?

Why do we lower a dough's hydration in summer but increase it in winter?

Of all the grains we eat, why are the wheats the only ones that exhibit elasticity?

Functionally, water wears many hats in food and biological systems, acting as a diluent (increasing free and overall volume); plasticiser (by hydrating and softening rigid macromolecular components by increasing mobility); solvent (by dissolving soluble molecules, ions or compounds); lubricant (by decreasing friction between between larger molecules and macromolecules); and the medium for biochemical reactions.

But not all water in a food system is available as solvent water, which is essentially the aqueous fraction where fermentative microbes live. Another way of conceptualising human food fermentations is to say that all microbial fermentations are a battle for solvent water. It is the fundamental resource in microbial warfare, literally the battleground where territorial disputes occur. Whosoever controls this “space” determines the outcome of a fermentation. In spontaneous or one-off fermentations, successions occur, with microbial dynasties rising and falling through time, each leaving behind a legacy, and shaping the landscape in ways we can taste.

Most of the principles I will cover have application to other food, biological and even physical systems. My aim is to elucidate what I see as the shared attributes of these systems, the commonalities that emerge due to unseen biophysical properties, and how we, as organisms ourselves, interact with these features.

Bread is often taught in a vacuum, with flour seen as an inert, passive ingredient whose functional characteristics are dumbed down to a “strength” exponent (e.g., W values, protein content, or flour usage type). The two primary goals of milling, reduction and purification, can likewise be seen in the entirety of our agricultural and food education and production. My hope is to connect the lifestyle of the things we ferment with or choose to eat to a much larger understanding of why our food is the way it is.

1. For total hydration: [14% moisture + 66.66% added water] / 86% flour solids, and then multiplied by 100. For total moisture, 94% water is divided by [94% total water +100% total solids] and then multiplied by 100.