A method used to protect valuable treasures, such as the Declaration of Independence, now preserves everyday grocery items.
To guard food from oxygen-induced spoilage, producers often blow pure nitrogen into packages to replace air, which is about 21 percent oxygen and 78 percent nitrogen. Typically, it takes about eight volumes of nitrogen to blow just one volume of air out of a package, says Kevin C. Spencer, a consultant who advised the British grocery chain Safeway Stores. Even then, 5 to 6 percent of a package’s gas remains oxygen, he says.