Making flour tortillas softer and more elastic
Taken from http://en.wikipedia.org/wiki/San_Francisco_burrito


  Two key technologies that made the San Francisco burrito possible are
  the large flour tortilla and tortilla steamers, which together
  increase the flexibility, stretch, and size of the resulting tortilla.
  The tortilla steamer saturates the gluten-heavy tortilla with moisture
  and heat, which increase the capacity of the tortilla to stretch
  without breaking. This in turn allows for the size of the San
  Francisco burrito. Corn tortillas, the original indigenous
  pre-Columbian form of the tortilla, cannot achieve either the size or
  the flexibility of the flour tortilla, and thus cannot be used to make
  a San Francisco burrito. A few San Francisco taquerias grill the
  tortillas instead of steaming them, using heat and oil instead of
  steam; and a few grill the finished product before the final step of
  wrapping it in aluminum foil.
  
  The aluminum foil wrapping, which is present whether the customer is
  eating in the restaurant or taking out, acts as a structural support
  to ensure that the tortilla does not rupture. One of the main
  difficulties of the San Francisco burrito is the issue of structural
  integrity, but skilled burrito makers consistently produce huge
  burritos that do not burst when handled or eaten. A successful large
  burrito depends on an understanding of the outer limit of potential
  burrito volume, correct steam hydration, proper wrapping/folding
  technique, and assuring that excess liquid has been removed from the
  burrito ingredients prior to inclusion.