It was debunked years ago. https://en.wikipedia.org/wiki/Five-second_rule https://en.wikipedia.org/wiki/Five-second_rule . In addition to the links given there,

It was debunked years ago. https://en.wikipedia.org/wiki/Five-second_rule https://en.wikipedia.org/wiki/Five-second_rule . In addition to the links given there, http://www.aston.ac.uk/news/releases/2014/march/five-second-food-rule-does-exist/ http://www.aston.ac.uk/news/releases/2014/march/five-second-... . Though as this new paper points out: "The rule has been explored by a single study in the published literature and on at least two television shows. Results from two academic laboratories have been shared through press release, but remain unpublished." That second URL is not peer-reviewed, and may be one of those press release results.