The Weird, Underappreciated World Of Plastic Packaging
Like it or not, plastic packaging has become an ingrained part of the food system.
While it's clearly wasteful to buy salad, sandwiches and chips encased in plastic and then promptly throw that plastic away, we take for granted how it keeps so much of what we eat fresh and portable.
And behind many of those packages that allow us to eat on-the-go or savor perishable cookies or fish imported from the other side of the globe is a whole lot of science and innovation.
The plastic revolution in food packaging began in the 1960s, says Aaron Brody, a food packaging consultant and an adjunct professor of food science at the University of Georgia. It took off because plastic was lighter than glass, more protective than paper and relatively cheap.
"But there is no such thing as the perfect plastic material," Brody says. So a lot of our packaging is made by combining different types of food-grade plastic.
Take a bag of potato chips. It's mostly made out of a plastic called oriented polypropylene. "It's an excellent moisture barrier," Brody notes. And that's key, "because potato chips first start to deteriorate by absorbing moisture. People don't like soggy chips." To further strengthen the material, many chips bags have a thin aluminum coating on the inside.
A layer of polyethylene (the stuff plastic grocery bags are made of) is sandwiched between this inner layer and the outer layer, which displays the brand and nutrition info.
Before the bags are all sealed up, most companies fill them with nitrogen gas, Brody says. "It keeps the chips from getting crushed," he says. And whereas oxygen would cause the fat in the chips to oxidize and taste funny, nitrogen doesn't cause any chemical reactions that affect the flavor.
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