Vol. XXIV · Bread Plate 3 of 12hydration, dough hydration, wet dough, stiff dough, bagels, sandwich bread, ciabatta, open crumb, sticky dough, water absorption, milk, egg, 含水率MT

Hydration.

The same flour and salt make a bagel at 57 % water and a ciabatta at 78 %. The water is the recipe.

Hydration is the simplest number in a formula and the one that most changes the bread. Low hydration (55–60 %) gives a stiff dough that is easy to shape and bakes dense and chewy: bagels, pretzels, many 馒头 (XXVI.3). Around 63–68 % gives the soft, smooth doughs of sandwich loaves, rolls and baguettes. At 70–75 %, rustic loaves are slack and sticky but bake into open, irregular crumb with glossy, gelatinised cell walls (VII.1); above 75 %, ciabatta and focaccia doughs are almost pourable and need folds rather than kneading (XXIV.4). More water also loosens gluten so it extends more easily, lets yeast work faster and slows staling (XXIV.11).

Hydration counts all the water: milk is about 87 % water and egg about 75 %, so an enriched dough with milk instead of water is less hydrated than its "liquid" figure suggests. And flour itself varies: high-protein and wholemeal flours absorb more water for the same feel (XXIV.1), as do fresh-milled and dry flours, so a formula's hydration is adjusted a few per cent to the flour in hand. The workshop sets the hydration.

Below: the hydration of a dough from the water, milk and egg you choose per 100 of flour (exact, counting their water content), placed on the scale from stiff bagel dough to wet ciabatta, with a cross-section of the crumb it tends to give.

What you will learn

Calculate hydration including milk and egg.
Match hydration to a bread.
Handle wet doughs.
Adjust hydration to the flour.

Workshop

Hydration = (water + 0.87 × milk + 0.75 × egg) ÷ flour, exact for those water contents. Bands from common bakery practice: stiff below 60 %, standard 60–68 %, rustic 68–75 %, very wet above 75 %. Crumb sketch: a teaching drawing, larger holes with more water.

Count all the water, then read the dough

A dough made with 60 % milk and no water has a hydration of only about 52 %, because milk is 13 % solids — which is why milk breads feel firmer than their liquid suggests and why recipes moving from water to milk add a little more liquid. With egg the same: a brioche with 50 % egg and 20 % milk is near 55 % hydration, firm until its butter softens it (XXIV.10).

Working with wet doughs: do not add flour to stop the stickiness; wet your hands and the scraper instead, and use stretch-and-folds in the bowl (XXIV.4); give them time — gluten develops by itself in a wet dough; shape with a bench scraper and a lightly floured surface, and bake on a preheated stone or in a covered pot for a strong oven spring (XXIV.9). If a new flour makes your dough feel too stiff or slack, change the water by 2–3 % next time and note it on the formula.

At the stove

Make the same small dough at 60 % and at 75 % hydration. Note how each feels, how fast it rises, and cut the baked rolls to compare the crumb.

Very wet doughs owe much to a 1982 invention: ciabatta was created by Arnaldo Cavallari near Venice as an Italian answer to the French baguette, at a hydration few bakers then thought workable.

Terms

Hydration: Water as a percentage of flour, counting milk and egg water.
Slack dough: A wet, loose dough that spreads.
Open crumb: Bread with large, irregular holes.
Stretch and fold: Lifting and folding a wet dough to build strength (XXIV.4).

Hydration sets the dough and the crumb: ~57 % stiff (bagels), ~65 % standard (sandwich bread), 70–75 % rustic and open, above 75 % very wet (ciabatta). Count milk and egg water, and adjust to the flour.

Sources

A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.