#How can I keep a sample of blood recognizable after being stored for centuries?

How can I keep a sample of blood recognizable after being stored for centuries?

I have a race of carnivorous mammals (the same from this question) for whom blood plays an extremely important role in cultural rituals. For complex cultural reasons, a member of this race (call him Fred) decides it's a good idea to preserve a few milliliters of his blood so that another member of his race will be able to perform a ritual using it several centuries later, at which point the main body of my story takes place.

I have a race of carnivorous mammals (the same from this question) for whom blood plays an extremely important role in cultural rituals. For complex cultural reasons, a member of this race (call him Fred) decides it's a good idea to preserve a few milliliters of his blood so that another member of his race will be able to perform a ritual using it several centuries later, at which point the main body of my story takes place.

Edit:

I suppose it doesn't have to be a liquid while in storage as long as it's immediately convertible back to a liquid upon recovery.

If it makes any difference, it's going to be stored at extremely high elevation. Low temperature, moisture, and air pressure. No soil, but maybe a few handfuls of rock dust. And of course Fred's body, which I imagine will mummify.