He told MailOnline: 'Bacteria could be printed on the packaging in some pre-determined location.

When the product arrives at its destination, someone would take the packaging material, print it on an agar plate [a petri dish] and then grow the bacteria under a pre-arranged growth condition.

When you buy a pre-made sandwich, you're really just paying for its elaborate packaging — plus a whole lot of salt, fat, and unnecessary additives.