ambience: soda pouring, fizzing
Anyone who’s ever opened a bottle of soda knows that sound. But why is it that even unopened plastic soda bottles lose their fizz over time? I’m Jim Metzner, and this is the Pulse of the Planet.
“The carbon dioxide that gives soda what people normally associate with as fizz is soluble and will dissolve into the wall of the plastic and be transported through the plastic and escape. In much the same way that air in your tires will eventually escape and the tire pressure goes down with time.”
Benny Freeman is an Associate Professor of chemical engineering at North Carolina State University. He’s been studying the effectiveness of plastic packaging.
“Any plastic will permit leakage of small molecules through the plastic. The current packaging materials for things like soda bottles have leak rates that are acceptable for large sizes, but become unacceptable for smaller size bottles or for applications like beer packaging which are more sensitive to things like oxygen coming in from the outside of the package.”
And that’s why you don’t currently see beer packaged in plastic containers.
“For an application like beer where beer is very very sensitive to even small amounts of oxygen, the major factor limiting the use of plastic packaging for beer is that oxygen from the surrounding atmosphere gets into the package and causes the beer to get stale or taste flat.”
But Professor Freeman and his colleagues are on the track of using new kinds of plastic which form more effective barriers. We’ll hear more in future programs.
Pulse of the Planet is presented by DuPont, makers of better things for better living.
