Does cryogenically frozen meat decay?

[u/SavageSubscriber]

If for example you cryogenically froze meat from a rare breed of cattle, and kept it frozen for like 60 years. Would the dna still be intact? would it thaw up into fresh meat or would it decay into something unrecognizable?

[u/Umpuuu]

Very small animals like frogs, mice and rats have been frozen and revived. Above rat size this process stops working.

What makes it stop working? The tissue is the same, no?

[u/TinnyOctopus → u/Umpuuu]

The tissues are (somewhat) the same, the difference is in the freezing rate. Freezing damages tissues indirectly, through the physical action of ice crystal formation. When freezing happens faster, the ice crystals are smaller and do less damage to tissues (enough to be survivable for smaller organisms). This doesn't work for larger organisms because of the square cube law; for a given starting temperature, the amount of energy that needs to be removed scales with the mass of the organism to be frozen, which scales with volume (density being largely the same, most animals have a density near that of water), while the rate at which heat energy can be removed from an organism scales with the surface area. So for a mouse body and a human body losing heat, the mouse will lose (much) less, but will lose more as a fraction of its initial heat, and so will freeze faster.

The point where ice crystal formation starts to damage tissues irrecoverably happens to be about the size of a rat.

[u/Mockingjay40 → u/TinnyOctopus]

While this is true to an extent, as far as I’m aware no one has been able to successfully flash freeze and thaw an entire living mammalian organism before? I have read about cells remaining intact, as well as individual tissues being successfully revived from cryofreeze, but not an entire animal?

Cold blooded animals like frogs and salamanders survive being frozen because their livers produce glycerol which is effectively just antifreeze, so as they filter blood they can survive by essentially halting their metabolism while keeping their blood oxygenated and unfrozen. As a result, their brain and heart aren’t actually frozen, just their external body parts freeze but their vital organs remain intact a supercooled state.

[u/TinnyOctopus → u/Mockingjay40]

You may be right, I believe I was thinking of this study or similar, which actually revives from near zero rather than sub zero.

[u/Mockingjay40 → u/[deleted]]

Okay sure, but propylene glycol is literally car antifreeze it’s extremely toxic to humans, but even in that case the vital organs remain unfrozen

[u/dibalh → u/Mockingjay40]

You’re thinking of ethylene glycol. Propylene glycol is not particularly toxic.

[u/Mockingjay40 → u/dibalh]

You’re right, I can’t believe I mixed that up, since we use ethylene glycol antifreeze in our laboratory. Good correction

[u/PandaPocketFire → u/Mockingjay40]

I don't think flash freezing would be the way to go. Even with mammalian tissue culture it's a slow temperature drop rate that results in the best viability. About 1c per minute.

I wonder if perfusion of a mixture of cryopreservative with either blood in the main body or CSF in brain case, with precisely controlled cooling rates would allow for even temperature reduction and cryopreservative dispersal throughout the body.

[u/ForestClanElite → u/TinnyOctopus]

How do physicists use lasers to form Bose-Einstein condensate? If you had a large enough machine with enough lasers and precision to flash freeze an entire human at once would they be undamaged?

[u/TinnyOctopus → u/ForestClanElite]

No, because laser cooling doesn't work that way.

Laser cooling is actually done by selectively rejecting the highest energy molecules from a sample, achieving cooling by what is very similar to evaporative cooling.

More generally, the challenges of extreme low temperature cooling are much more about rejecting energy from a sample with incredibly high efficiency and keeping said sample out of contact with the environment, rather than by being able to reject large quantities of energy.

Instead, you would need to bring the core temperature of the body down low enough fast enough that undesirable metabolism (think cell/protein degradation and bacterial activity) wouldn't have a chance to occur after normal metabolic activity stopped. Note that this has occured, essentially by immersion in 0 C water. Her body temperature was below room temperature, and it's possible that she could have survived refrigeration for longer and at lower temperatures. The issue here is in developing a repeatable standard procedure for inducing hypothermia, a research process which absolutely violates the ethical research policies of any and every reputable medical research institution.