US Army's hi-tech, two-year-old sandwich served fresh

A sandwich which stays fresh for up to two years has been developed for the US army as Dr George McGavin found out as part of his investigation into what happens when food rots.

After Life: The Strange Science of Decay will be broadcast on Tuesday, 6 December, 2011 at 21:00 GMT on BBC Four. Or watch online later via BBC iPlayer at the above link (UK only).