Filed by KOSU News in Science.
December 15, 2011

For the U.S. military around the world, the enemy can be hard to pinpoint and even harder to defeat. But back at home, the Army has a tiny and vexing foe in its sights: the bacteria that cause food to rot.

In this bacterial battle, though, it’s clearer who’s winning, and the evidence is a humble pocket sandwich, which looks from the outside no different than your average hot pocket in the frozen foods aisle.

But this sandwich is spectacularly resilient to threats (or hurdles, in Army speak) that would turn it into a dry, moldy mess if they could. Unlike probably any other sandwich out there, this one keeps the microbial forces of nature at bay for up to two years.

How on earth could a BBQ chicken sandwich stay fresh for two years, you ask? And is it even edible? (Yes, according to soldiers interviewed by the BBC. One said, “I’m a big fan.”) We were still puzzled, but fortunately senior food technologist Michelle Richardson was happy to explain.

According to Richardson, who concocts food for the armed forces as part of the Combat Feeding Directorate at the U.S. Army Natick Soldier Research, Development & Engineering Center in Natick, Mass., the trick to extending shelf life is figuring out how to control pH, water activity, moisture content, and oxygen inside the packaging.

“If you think about bacteria as sprinters in a food system, what we’re trying to do is put enough hurdles in so they can’t survive,” Richardson tells The Salt. She says the hurdles include lowering the pH, binding the water to something the bacteria can’t use it, and adding a packet of “oxygen scavengers,” or iron filings, to absorb the oxygen so that it’s not available to bacteria, yeast and mold. “All this keeps the bread, meat and filling from going rancid,” she says.

Her Army laboratory might seem an odd site for some of the most sophisticated thinking on food preservation. But the CFD has a tough directive — to provide soldiers with something to nosh on while in perilous and eatery-free environments — that seems to inspire creativity.

The food they make has to be easy-to-eat, relatively tasty, nutritious and long-lasting. Rations typically make a long journey from the plant where they’re manufactured to the troops in the field; they could easily sit in storage on a base for several months before ever seeing the light of day.

The Natick lab is also the home of the famous Meal-Ready-To-Eat, or MRE – the main sustenance for troops in the field, which is designed to be stored for up to three years without refrigeration, and survive a drop from a helicopter.

But it became clear in the early days of the Iraq and Afghanistan wars that some troops in “high intensity combat operations” were weighed down by the MREs and couldn’t heat or prepare some of the entrees. So the CFD scientists began looking for another way to feed them.

Richardson says troops had always been requesting sandwiches, so they developed the First Strike Ration, which can include the long-lasting pocket sandwich.

Even though she’s proud of the resilience of the pocket sandwich, Richardson says there’s another big challenge looming on the horizon: pizza cheese.

“It would be really nice if we could make a pizza ration,” says Richardson. “The problem is that when you make it shelf-stable, you have to remove the moisture. Then it won’t melt and the eating quality is totally different.” [Copyright 2011 National Public Radio]