be careful using colour to determine doneness in a burger.
game meats like bison and elk take a very long time for the "red" to be cooked out in the center. if you cook it that long, you'll end up with something better suited for a hockey rink than a bun.
as far as contamination goes, i prefer my burger rare and bloody, but i would never serve one that way unless requested.
in nomine patri, et fili, et spiritus sancti.
beidh ar la linn.
wisdom is often in short supply within ones' ego.