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Culinary Lesson #19 - Flour

Monday, October 21, 2013

We've all probably experienced this (or something similar) at least once in our lives.  You find the perfect baking recipe to try, but notice at the last minute that it calls for cake flour rather than the more common all-purpose flour.  If you don't have cake flour, can you use all-purpose flour?  Or is there a substitute for the job?  What's the main difference between common types of flours?

Images from www.kingarthurflour.com.
Before we look into the similarities and differences between common types of flours, let's go over a few key terms.

  • The 3 Parts of a Wheat Berry:
    1. Bran is the hard outer layer that contributes to roughly 14% of a wheat berry, by weight.
    2. Germ is the embryo of the berry and contributes to roughly 3% of a wheat berry, by weight.
    3. Endosperm is the starch of the berry and contributes to roughly 83% of a wheat berry, by weight.
  • Bleached vs. Unbleached Flour:
    • Bleached flour is any flour that has been chemically altered (typically using benzoyl peroxide or chlorine gas) to speed up the aging process while also whitening the flour.  Typically bleached flours have less protein than their unbleached equivalents.  Although some people can taste the difference between products made from bleached versus unbleached flour, the main reason consumers buy bleached flour is for the 'improved', whitened color.
    • Unbleached flour is any flour that has not been chemically altered and has thus been allowed to age naturally.  Unbleached white flours (such as all-purpose) will have a slight yellow tint to it.
  • Protein Content:  The protein content of flour directly indicates the gluten potential (as was briefly mentioned in an earlier culinary lesson).  The higher the protein content, the more gluten can be produced, and the chewier the baked good will be.  The lower the protein content, the less gluten can be produced, and the more tender and crumby the baked good will be.  Flours ground from hard wheat contain higher protein contents than flours ground from soft wheat.

The following is a list of what I feel are the five most common types of flour in a home cook's kitchen.  They are organized by protein content (lowest to highest) and include general descriptions and substitutions (if applicable).

  • Cake Flour:
    • General Description:  Known for its low protein content, cake flour is used in baked goods that aim for light, tender textures.  It is usually bleached (chlorinated) and used in recipes that call for chemical leavening agents rather than yeast.  Unlike most flours, cake flour is usually sold in a box rather than a bag in grocery stores.
    • Average Protein Content:   6% - 8%.
    • Substitution:  Take 1 cup all-purpose flour, subtract 2 tablespoons of all-purpose flour, and add 2 tablespoons cornstarch.  Pass the mixture through a sifter twice to ensure that the cornstarch is evenly distributed.  Thus, cake flour is 12.5% cornstarch and 87.5% all-purpose flour, by volume.
  • Pastry Flour:
    • General Description:  Pastry flour falls in between cake flour and all-purpose flour when it comes to its properties.  Because of this, baked goods that use pastry flour are slightly chewier than if they would have used cake flour, but more tender than if all-purpose flour would have been used.
    • Average Protein Content:  8.5% - 9.5%.
    • Substitution:  Although the exact ratio will change depending on the protein content you're starting with, a common substitution includes combining 1 cup cake flour with 2 cups all-purpose flour.
  • All-Purpose Flour:
    • General Description:  As the name suggests, all-purpose flour is the go-to type of flour when it comes to baking.  Its white color comes from the fact that only the endosperm is ground and used (rather than the outer bran layer and germ, in addition).
    • Average Protein Content:  10% - 12%.
  • Bread Flour:
    • General Description:  Known for its ability to produce gluten, bread flour is used for any type of bread that is meant to be chewy and is often used with yeast rather than chemical leavening agents.
    • Average Protein Content:  12% - 14%.
  • Whole Wheat Flour:
    • General Description:  Known for its nutritional benefits, flavor, color, and high protein content, whole wheat flour is most commonly used in rustic yeast breads.  As the name implies, the 'whole' wheat berry (bran, germ, and endosperm) is used.
    • Average Protein Content:  14+%.

So now looking back at the original question, you can see that there are several factors that come into play when determining the best type of flour for a recipe and if a substitution would make sense, if needed.  Questions you need to ask yourself include (1) what type of protein content your base flours have, (2) what type of texture you anticipate the final product having, (3) the age and condition of your flour, and so on.  Thus, there is no such thing as a cut-and-dry substitution for flours since the properties vary so much.  But (luckily) there are general guidelines to get you started.  It's all about making educated decisions and judging how you did through trial-and-error.

Information for this post came largely from The New Best Recipe, theKitchn, and King Arthur Flour.

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