27 Feb 2014 Three-year pizza to join US Army MRE delicacies
Military science, or rather food science, is close to completing its most epic and delicious quest yet — to put pizza in the US Army’s infamous rations or MREs, aka Meal, Ready to Eat.
MREs have a long and checkered history, acquiring such nicknames as “Meals Rejected by Everyone” and “Materials Resembling Edibles”. Pizza has long topped the list of requested meals by soldiers, but the task of providing a palatable slice of this complex food that will survive the required three-year shelf life has foiled all attempts.
“Since the dawn of time — almost — pizza has been one of the most requested and sought-after components in an MRE,” said Jeremy Whitsitt, of the Army Natick Soldier Research, Development and Engineering Center in Massachusetts. “We’re finally cracking the code in getting the crust and the cheese and the meat to all live happily in a pouch for three years, without refrigeration.”
MREs are the basis for feeding assault troops engaged in battlefield combat action. Each MRE provides 1300 calories of high-fat, high-sodium nutrition suited for active combat duty.
The nominal shelf life of an MRE is three years at a storage temperature of 27ºC, but they must also be able to survive short exposure to temperature extremes from -51ºC to 49ºC. MRE packaging must be able to survive parachute deployment from an altitude of 380m, and a free fall drop from 30m.
Much more difficult than satisfying these physical and chemical requirements, however, is satisfying people’s instinctive response to a food. The problem is well known in humanoid robotics, where it is called the uncanny valley.
If the characteristics and behaviour of a humanoid robot are very close to those of a natural human, people will accept the robot as an entity that might be a friend. If the approximation of human characteristics is poor, the robot will still be acceptable as a separate, non-humanoid entity. However, if the robot appears close to human norms, but not close enough, the robot will be rejected as strange and dangerous.
People also have an uncanny valley when it comes to food acceptance. It is often easier to come up with a new dish than to try to reproduce one that is enjoyed and valued. A new dish will be evaluated on its own merits, while a reproduction will be compared to an existing standard.
For example, a slice of pizza which has a soggy crust and an oversweet taste will be evaluated differently than a sweet tomato bread pudding with cheese and meat topping. It all comes down to expectations, but our expectations can present extremely powerful barriers to surmount.
So how do you make a slice of pizza that will survive three years unrefrigerated that still appears, smells, tastes, and has the mouthfeel of a fresh slice of pizza? Natick senior food technnologist Michelle Richardson took on the task after non-soggy sandwiches entered the MRE choices in the 1990s.
Pizza is a complex food consisting of four major components: bread, sauce, cheese, and sausage (pepperoni in this case). Each of these components has different characteristic levels of moisture, acid, and texture, which must combine harmoniously to produce a slice that will generally be viewed as a “good pizza.”
In contrast, another combination of bread, sauce, cheese, and sausage made from a hardtack biscuit covered with ketchup, Roquefort cheese, and finely chopped hot dogs won’t remind anyone of a good pizza.
Richardson had to reach deep into her bag of tricks to pull off the new pizza. The pizza dough had to be enhanced with humectants, substances like propylene glycol or sorbitol, that bind moisture within the bread. This both reduces the possibility of bacterial growth and the tendency of the sauce to make the crust soggy.
Another problem encountered with bread products is that they go stale with time. Contrary to popular opinion, staling is not caused by the bread drying out (which would be counteracted by humectants). Instead, the moisture in the bread migrates within the bread, causing the starch granules to recrystallise. In the end, Richardson and her assistants used gums and enzymes to hold the water within the starch granules, making the pizza crust shelf-stable…..