It would seem that the ultra-cold vacuum would kill off most of the bacteria, etc in the body, as well as quickly boil off all of the water content. Here's a lovely description of the process from Focus magazine:
In space we can assume that there would be no external organisms such as insects and fungi to break down the body, but we still carry plenty of bacteria with us. Left unchecked, these would rapidly multiply and cause putrefaction of a corpse on board the shuttle or the ISS. Drifting exposed in the vacuum of space itself, however, this process would rapidly slow to a halt.
The low pressure would initially boil off most of the water and what was left would freeze, halting any biological processes. Depending on the trajectory of the corpse, there might be some warming from the side facing the Sun, but all this would do is accelerate the rate of water loss, leaving only a dried husk.