The Science Of Feeding Soldiers in Chemical & Engineering News
Marines warm up with a hot MRE during a cold-weather training exercise.
May 5, 2010 - Washington, DC
By Bethany Halford
When Neil Gussman joined the Army in 1972, meals for the battlefield were served in little green cans. Open those tins, recalls the Chemical Heritage Foundation's communications manager and Army sergeant, and you were likely to find culinary delights like "gelatinous, fat-coated Spam slices" and "big wads of grease."
Known as C rations, "the 12 main courses were ham and eggs, beans and franks, spaghetti, ham slices, and permutations of Spam," Gussman says.
He reenlisted in 2007 and, to his pleasant surprise, found that the green cans had been replaced with sleek tan packages stamped "MRE," for Meal, Ready-To-Eat.
"When I got my first MRE, I was in gastronomic love," Gussman says. Inside were crunchy crackers, brand-name candy, and a heating bag that gave off no smoke or light signature. Tactical eating no longer meant meals of congealed fat, he says.
But moving from cans of "green eggs and ham" to pouches of moist lemon poppyseed cake and hot beef ravioli requires a lot of scientific innovation. "Everything in the MRE involves chemistry in some way," says Jeremy Whitsitt, the Department of Defense's combat feeding outreach coordinator. From the packaging designed to withstand downpours and airdrops to the chemical heater that warms meals and beverages, the Combat Feeding Directorate at the U.S. Army Natick Soldier Research, Development & Engineering Center (NSRDEC), in Natick, Mass., has spent years developing the modern MRE.
The unpredictable nature of military life means that battlefield meals must meet a set of strict criteria. MREs need to maintain their freshness for three years when stored below 80 °F, or six months when stored below 100 °F. "They must also be able to withstand rough handling conditions and airdrops from altitudes of 100 feet by helicopter, without a parachute, or 1,200 feet by plane, with a parachute," Whitsitt says.
An MRE's packaging presents the first line of defense in keeping it from getting beaten up during transport and in preventing oxygen, water vapor, and insects from infiltrating and spoiling the food. "It's a critical part of the overall MRE," says Danielle Froio, an NSRDEC materials engineer.
It's also the first thing you notice about an MRE as you pull apart the seal of its tough, tan meal bag made of low-density polyethylene. The food inside this bag is stored in two types of pouches, Froio explains. There's the retort pouch, which holds food that's been sterilized, and the nonretort pouch, which houses food that doesn't need sterilization.
Both pouches have a polyester outer layer that's easy to print on, so nutritional information is included with each of the MRE's components. Beneath the polyester is a layer of foil, which, Froio says, is the ultimate barrier to oxygen, water vapor, and light. A polyolefin layer also makes it possible to seal the package. And retort pouches have a fourth layer of nylon to make them durable enough to withstand the rigors of the sterilization process...
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