What did edward throw on his plate in the lunchroom and why?

As they were filming the scene, for some reason the Cullen cast were eating. In one shot it is clearly seen Kellan Lutz (Emmett) is chewing on a rice krispie treat. In another Rosalie is chewing and holding a cookie. Edward is throwing down a cookie. He explains to Kristen Stewart (Bella) and Catherine Hardwicke (director) in the audio commentary That he threw down a cookie and said "Havn't you guys read the book? We're not supposed to be eating!"