Based on the evidence at WORLDS OLDEST HAMBURGER: The Hamburger’s Story, the answer seems to be “forever.” The hamburger in this picture rolled out from under McDonald’s heat lamps back in 1999 (you know, back when Slick Willie was in the White House), making it now 13+ years old.
Yet, the meat and bun (or maybe it should be “meat” and “bun”) somehow have no visible signs or smells of aging. Interestingly, the burger’s owner, David Whipple, noted that the pickle rotted away some time ago – you know, like real food is supposed to do.
What’s the secret to its youthful look, you may be asking. I don’t know, but it’s a little bit scary, isn’t it?
Photo courtesy of David Whipple at http://oldesthamburger.blogspot.com (thanks David!)