They call it the holy grail of ready-to-eat meals for soldiers in combat or remote areas — a pizza that can stay on the shelf for up to three years and still be edible.

Researchers at a U.S. military lab in Massachusetts are closing in on the pizza that soldiers have been asking for since 1981, when lightweight individual field rations replaced canned food in combat zones or areas where field kitchens can't be set up.

On-and-off research over the past few years has helped them figure out ways to prevent moisture from migrating to the dough, creating conditions for potentially dangerous bacteria.

Researcher Jill Bates says the latest prototype batch of pepperoni is like a typical pan pizza, with a crust that's a little moist and not super-crispy.