In order to keep abreast of current trends in gluten-free technology from the consumer perspective, the author recently purchased the gluten-free cookbook put out by the writers at
America’s Test Kitchen. The
company’s so-called The How Can It Be
Gluten Free Cookbook (2014) is something of a mixed bag; many of the
recipes are retooled versions of their particular recipes, such as their
five-banana banana bread, for particular gluten-free reformulations available
to the lay cook. Some of the recipes are nothing more than a bit of legerdemain
to fill space and were never contaminated by gluten to begin with, however, and
the book does lose some points for this bait-and-switch maneuver. For the
recipes that are present, however,
the cogent and usually decently accurate depictions of the chemistry
accompanying the processes and the storytelling of how each variation of a
recipe was tested are useful guides to the home cook.
This post is not intended as a review of the book, although I consider it a worthy enough text. Rather, I want to dedicate the present discussion to a curious observation made within its pages on the superiority of psyllium husk in yeast-dough baked goods, such as pizza crust and sandwich breads. The Editors at
Test kitchen attribute this to the fact that it “binds more effectively with
water… [as] a result, psyllium does a better job of strengthening the protein
network so it is capable of holding in lots of gas and steam during baking” (p
16). Later, the Editors write that “its chemical composition is similar to that
of xanthan gum, but it has a higher viscosity, so it is able to bind water even
more effectively… psyllium interacts strongly with the proteins in gluten-free
flours… providing a strong enough structure to support highly leavened bread
once the bread cools” (p 21). The Editors note that this advantage is only
observed in yeasted products; chemically-leavened doughs and batters were
generally drier and had an objectionable texture when psyllium was used (p 16).
These statements are, to my eye, somewhat conflicting. They raise several key questions that will be explored here:
1.) Is the mechanism as to why psyllium works in the way that it does strictly related to its viscosity?
2.) Is the chemical structure of psyllium truly comparable to that of xanthan gum?
3.) What is the reason for psyllium’s superior performance in yeasted products in particular?
4.) What is the reason for the comparatively poorer performance of psyllium fiber in chemically-leavened breads.