Cheers! Thanks for getting back to me.
Food poisoning is unappealing and it's why I've put it out there. I was at boarding school...
"Resists cooling to a safe temperature" had me thrown though. I apologize if my response seemed a touch ungracious.
Anyway, so I've scraped the still warm Hollandaise from the siphon into a plastic container and put it in the fridge. Usually there's only about 100ml leftover Hollandaise (don't scoff, it's enough to put on a Benedict), The fridge is at 2 deg and I'm not too worried about it (100 ml) adversely effecting the temperature of the surrounding food.
So, if the egg has been cooked at 65 deg for 30 min and then gets 2 hours more at 55 deg. It's got salt and Citric Acid. Does that count as pasturised?
My BIG question is: "does anyone actually know how long you can safely keep it in the fridge?".
PS. But you could have just said "are you reducing the kinetic action of molecules in the bounding material faster than the perversely thermal properties of the foam - by using nitrogen? ", and I would have been right there.