Why does my cat maul our bread?

My 13 year old cat has a strange behavior that we're curious about. If I leave any loaf bread or pastries (such as doughnuts) anywhere she can get to them, she will maul them. It looks like she chews on them through the plastic packaging, just enough to make it inedible for us. However, if I put the bread, etc., right in her bowl, she won't eat it. Why does she do this! Is it fun? Is she lacking something? Is it a combination of things? It's really irritating!