But Butter Goes Rancid In The Freezer

A quick Google search suggests that rancidification/peroxidation rates under LN2 storage are considered negligible for food storage purposes: LN2 is being investigated as an alternative to freezing for this very reason. LN2 also appears to slow down or stop rancidification in cryopreserved tissue (paper). Nevertheless, there are concerns about rancidification during the freeze/thaw process. Also, this does not give much info about the outcomes of long-term storage (decades and possibly centuries) as required in cryonics.

Noticing my confusion: I do not believe that butter goes rancid in the freezer.

See Alcor's stock answer to this. The Arrhenius equation is mentioned.

I'm an biochemistry major, so organic chemistry takes up a large part of my time. I'm still just a lowly undergrad, though, so Google will probably do as well as me. In any case, here are my thoughts:

1. Rancidity is caused by several mechanisms: mostly hydrolysis, various microorganisms about which I know nothing, and oxidation. I do not think butter will go rancid in liquid nitrogen, since it would need water, microorganisms, or oxygen to do so. I imagine rancidification is slowed at cryogenic temperatures, but I'm not sure if oxidation and hydrolysis would completely stop.

2. I don't see why they wouldn't be... but given the site we're on, I'm hesitant to come right out and say yes.

3. I would suspect this question is not answerable with any precision at this time.

4. The presence of oxygen is certainly relevant to randification normally, so I would guess so; but don't quote me on it.

I can't answer your specific question about rancidity, but it's no secret that the whole process causes pretty severe molecular damage, so either way you'll be counting on future science's ability to reconstruct you with less-than-perfect information.

1. Chemistry pretty much stops at LN2 temperatures. You're not going to go rancid.
2. If your brain is frozen in LN2, you have pretty big problems already. But it appears the information is not lost. (As far as we presently understand.) Just we don't know how to get it out again.

1. The boiling point of oxygen is about 90 kelvin (13 degrees higher than nitrogen's boiling point). If the liquid around a cryo-patient is not changed over time then we might expect the ratio of liquid oxygen to liquid nitrogen to increase over time. Is the presence of the liquid oxygen relevant to rancidty issues or not?

probably not:

At the temperature of liquid oxygen, most bimolecular chemical reactions are largely inhibited. The rates of these reactions, in general, decrease rapidly with decreasing temperature. At very low temperatures the rates become too small to be measured, and for practical purposes it may be said that reaction ceases. This is especially true of oxidations, since, for example, neither sodium nor phosphorus immersed in liquid oxygen undergoes any apparent oxidation.

Based on my even more limited high school chem knowledge, I would say that oxygen turning into a liquid would speed up the process (faster than it would have occurred at 77 Kelvin), as things dissolve in liquids more readily than gases. So, if oxygen is in the rate law for fats turning rancid, this would increase the rate that it happens at.

Of course, there's a very good chance that due to the dependence on microbes this reaction wouldn't occur at all.

One elementary point I have not seen made yet is that a superintelligence can probably extract information from a rancid brain as easily as a non-rancid one although before the arrival of the superintelligence, it might be more likely for certain kinds of damage to happen to a rancid brain. Like others, I almost did not participate in this thread because someone who really knows the subject matter could probably give a vastly more definitive and credible answer.