Food Unwrapped's Lunch Box

Kate Quilton finds out if there is any difference between soft and crusty bread rolls, and Andi Oliver reveals why chocolate chips don't melt when baked in cookies. Andi also asks why pre-made sandwiches always seem to have mayonnaise in them, Matt Tebbutt uncovers some of the secrets of ready meals and Briony May Williams discovers the surprising science of how canned food can last so long.