What property does rice flour add to a shortbread recipe?

Question

I bought a book with recipes for shortbread as I wanted to try making my own shortbread. However, most unusually (given its general availability in shops), many of the recipes call for rice flour in addition to wheat flour.

What would be the effect expected from rice flour in a shortbread recipe and is there a more commonly available substitute (I was thinking potato or corn starch, but I am unsure)?

Answer 1

There are numerous recipes also calling for corn flour or corn starch instead of rice flour; so you can substitute with any gluten-free and low-protein flour or starches (also potato starch). The idea, is pretty simple actually, cutting down the protein content of the mixture.

Considering there's a good amount of fat in the shortbread, it will inhibit the development of gluten.

Adding riceflour will help you utilize these two measures, in our battle against gluten development, resulting in moister and less chewy end results.

And please note that, afaik, the traditional recipe actually calls for oat flour. (which, i believe, is also gluten-free)

Answer 2

The purpose of the rice flour is to add starch without protein, thus reducing the overall protein content of the dough and making it "softer" and more tender. Its inclusion is traditional in some recipes, and older than you'd think (19th century). It's also supposed to make cookies "crisper", but I haven't observed this myself. There's a number of ways to work around this requirement if you don't have rice flour on hand. Note that all of these will change the resulting shortbread from the exact texture of the original recipe, but you might like the result anyway.

• use all wheat flour, but use a lower-protein flour if you have it (e.g. "pastry flour" or "cake flour")
• use another short flour in place of the rice flour, such as fine-ground corn flour or tapioca flour (not starch). This will change the flavor, but might be interesting.
• use a pure starch to soften the flour, such as corn or potato starch as you suggested

For the last option, since those starches have no "body", I'd suggest changing the ratio. While cookie recipies may be up to 1/3 rice flour, a more reasonable portion of corn starch is 1/8th portion corn starch, as you would to substitute for cake flour.

Finally, note that if you can't find rice flour near you, you can make your own using a high-speed blender or a food processor and white rice. Might take a bit of work, depending on the amount you need, though.