Among the infinite variety of Easter candies, Peeps are unique. It’s not their shapes (they come as eggs, bunnies or chicks) or their shrieking neon colors. What sets these ubiquitous treats apart is their texture-a squishy-soft mixture of marshmallow and sugar kind of like a tiny seat cushion. Crafting that sugary sponge involves some simple food chemistry, says CALS food scientist Rich Hartel, who writes about Peeps in his new book, Food Bites. Here’s how the perfect Peep is hatched:

Mix the basic ingredients. Like most candies, Peeps start out as a warm solution of sugar and corn syrup. Colors and flavors are added to this gooey slurry, as well as gelatin.

Add air. The slurry passes by a heating tube to whip in zillions of tiny air bubbles to make the mixture foamy. Here’s where the gelatin comes in. Gelatin adheres to the surface of air molecules, surrounding the bubbles and keeping them intact throughout the process. Sugar and starch molecules slide in between the gelatin-encased air bubbles.

Squirt the shape and sugar up. The fluid marshmallow goo is squeezed through a nozzle that traces the desired shape on a conveyor, like using a tube of icing to decorate a cake. Colored sugar crystals rain down to coat the newly hatched Peeps as they rush by. Eyes, made of carnauba wax, are then painted on.

Sink your teeth in. Fresh Peeps should have a pillowy softness in your mouth. But if a package is left open in low humidity, the matrix of sugar molecules can dry out, creating what Hartel calls “petrified Peeps.” Some fans claim that’s the only way to eat them.

This article was posted in Food Systems, Know How, Spring 2009 and tagged Food and drink, Food Bites, Food science, peeps, Rich Hartel.