As ubiquitous as pizza is in America, it proved very hard to perfect as a field ration. Make the crust too dry, and you end up with hardtack; too moist, and it molders in the pouch. It took years to develop a spongy, stable bread with just the right amount of moisture, trapped with a blend of gums, oils, sugars and a touch of glycerol.
Adding cheese, sauce and meat brought a barrage of new problems. Moisture would migrate from one ingredient to another, drying out the sauce and turning the crust to mush. Oxygen hiding in the hole structure of the bread turned the cheese brown and the pepperoni rancid. (The same issues ultimately sank the directorate’s attempt to make an M.R.E. peanut butter and jelly sandwich.)
The food scientists kept tweaking the pizza’s cheese, bread and sauce until they all had the same level of moisture and the same pH, so they would not interact and spoil. And to fight oxidation, the team added a small sachet of iron filings to the sealed pouch, which will bind any free oxygen.