How to keep wheat
flour tortillas (the soft, white tortillas shown here) fresh is the subject of
ARS studies on staling. Click the image for more information about
story to find out more.
A Tortilla's Freshness Is Wrapped Up in Its
Wheat By Erin
September 13, 2004
They're the foundation for burritos, tacos, sandwich wraps and
other popular foods, but wheat tortillas are most tasty and functional when
they're soft, tender and less than a couple of weeks old.
Hoping to give tortillas a longer shelf life to satisfy frugal
consumers, Agricultural Research Service
chemist George Lookhart is studying the causes of staling in aging tortillas.
With that insight, he'd like to someday stall the everyday occurrence of
staling, which scientists have been trying to explain for more than 150
According to Lookhart, the perfect tortilla is about 2
millimeters thick and evenly opaque, with ample diameter and at least a 3-week
shelf life. He recently developed a test that can determine whether a
particular wheat flour will yield this ideal tortilla.
His research and the new testing method could eventually help
the tortilla industry and breeders develop wheat varieties ideally suited for
Lookhart, who works at the ARS
Grain Marketing and Production Research
Center in Manhattan, Kan., bases a tortilla's quality partly on how strips
of the flat breads perform when being stretched across a special plate. He then
measures the forces involved in this stress test and determines the level at
which they cause the tortilla strips to break.
A wheat tortilla's tenacity is largely dependent on the kinds of
proteins that are found in its flour. Known as gluten, the proteins can impart
strength to a tortilla, allowing it to endure the stress of being rolled up
But when flour from a particular wheat variety has excessively
strong gluten, says Lookhart, the tortilla made from it will have too much
"spring"--causing it to shrink in and lose valuable surface area when the dough
is released from the tortilla press. Finding the right balance of proteins is
an important part of the wheat-breeding research.
more about Lookhart's wheat tortilla studies, see the September issue of
Agricultural Research magazine.
ARS is the chief scientific research agency of the
U.S. Department of Agriculture.