Wednesday, June 24, 2009

Formula for Hydration Percentage

The new GQ magazine features a list of what Alan Richman (GQ's resident food critic) believes are the 25 "best" pizza places in the U.S. I won't go into the details of which restaurants made the list (you can find them online already) or why they made the list. The pizza issue did get me thinking about once again making pizza at home. I saw an interview with Anthony Mangieri, owner/pizzaiolo of New York's Una Pizza Napoletana, where his advice to home cooks was to use a very wet dough since home ovens lack the required juice to cook a pizza properly (in excess of 700° F) and will dry out the dough due to its relatively low temperatures (in an excellent resource for pizza making, Jeff Varasano wrote: "Try baking cookies at 75 instead of 375 and see how it goes").

So all this talk about pizza and pizza dough got me thinking about Baker's Percentages and subsequently Hydration. Certain formulas called for hydration to be at around 65-70% (again for the home oven). Immediately I went searching for the mathematical formula for hydration but to no avail. I began to wonder why it was so elusive? I recalled Ruhlman's most recent book Ratio:The Simple Codes Behind the Craft of Everyday Cooking. I reasoned that where there were ratios, there were percentages. The book states that the basic bread dough has a ratio of 3 parts water to 5 parts flour and the quantity of any other ingredients are negligible.


I have checked the (mathematical) formula against existing dough recipes (formulas) with known hydration percentages and, lo & behold, the numbers work. What follows is a brief excerpt from my personal recipes which I have in HTML format; very much a work in progress but getting closer to done every day. Also, if you spot an error either in concept or computation please let me know. Thank you.

From the file:

"Dough Formulas: Hydration, Measures, & Process

The two most important factors to keep in mind when making bread are Hydration and Process. As far as hydration goes, here's a little equation that explains it all: Hydration = (liquid/dry). Whether you're measuring in grams, ounces, or pounds is irrelevant so long as the units are consistent. Problems arise during inconsistencies in metrics, if you measure your flour by weight and the liquids by volume there is going to be an issue. Without getting too much into the Physics involved (Density as it relates to Mass as it relates to Volume as Mass relates to Weight relates to etc.....) long story short: a fluid ounce of water is close enough to its ounce by weight (an avoirdupois ounce) such that it is negligible for baking if not space travel (1 fl. oz. of water =approx. 1.043 avoirdupois oz of water).
In conventional home cookbooks liquids and dry ingredients are both specified by volume. I suppose the thinking there was a "close enough" approach with respect to varying densities of all liquids and dry goods (both in and of themselves AND how they interrelate!!!!!), and figuring that home cooks will never, ever, need to scale a recipe or formula. What it all leads to is inconsistency. If you measure by volume exclusively and, all things being equal, your breads result in varying degrees of success from batch to batch now you understand why. If you can live with that more power to you and on with the formulae. If you want consistency and the ability to scale up or down, invest in a decent scale and weigh everything. You will yield consistent results and play with hydration to adjust end product to your tastes using the equation above.

Quick example: to find the hydration percentage to Michael Ruhlman's White Bread Ratio (5 flour:3 water)
Hydrtn% = (liquid/dry)*100
Hydrtn% = (3/5)*100
Hydrtn% = .06 * 100 = 60%
Simple algebra will show you how to adjust liquids and/or dry ingredients to achieve a desired hydration (assuming units are in grams for this example)

65% = (liquid/400 g Flour) * 100
.65 = liquid/400 g Flour
400 * .65 = liquid
260 g = liquid "

QED! (well...not really)

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