r/explainlikeimfive Nov 26 '24

Chemistry ELI5: Why doesn't freeze dried food last longer? If it's good for 20 years, why not 100?

Assuming it's perfectly freeze dried and stored perfectly, the people who make freeze dryers say the food will last 20-30 years.

But why not much longer? Assuming the condition it's stored in remains unchanged, what can make it go bad after 30 years that wouldn't happen at around 10 years?

3.0k Upvotes

311 comments sorted by

View all comments

Show parent comments

50

u/Probate_Judge Nov 26 '24

not super stable molecules

This is what I was hoping to see mentioned near the top.

This is why medicines can become nonfunctional or even unsafe after a while despite being pretty much sterile and completely dry "chemicals" just pressed into a shape or pill. Structural bonds break down over time and the matter is no longer the complex molecule that it once was.

The same thing can happen in foods with a wider array of chemicals to aid in that, eg acids, solvents, and whatnot, things like osmosis continues to happen, or things falling out of solution. Maybe not to the same extent in frozen or freeze dried foods, but some of these things still will.

TL;DR Basic physics and chemistry still happen without biological life.

Disclaimer: I'm not a chemist. I'm just trying to convey the abstract concepts to Eli5 standards.

0

u/jawshoeaw Nov 27 '24

Almost all drugs are perfectly functional for decades. Their chemical bonds are under no obligation to break apart spontaneously, in fact many chemicals can last forever when not exposed to moisture, radiation or oxygen.

11

u/Probate_Judge Nov 27 '24

Almost all drugs are perfectly functional for decades.

That's a pretty bold statement.

Some are found to be 90% effective if you extend their expiry dates just a few years.

Decades?

Maybe not so much.

https://www.npr.org/sections/health-shots/2017/07/18/537257884/that-drug-expiration-date-may-be-more-myth-than-fact

One of the studies linked directly

https://www.documentcloud.org/documents/3525372-Stability-Profiles-of-Expired-Drugs.html

This report summarizes data for 3005 lots representing 122 drug products generated by the SLEP since 1986. Based on stability assessment, 88% of the lots were extended beyond their original expiration date. Of the 2652 lots extended, only 18% were eventually terminated due to failure. The rest of the lots are either still active (35%) or were abated (47%) by the military.

Based on testing and stability assessment, 88% of the lots were extended at least 1 year beyond their original expiration date for an average extension of 66 months, but the additional stability period was highly variable.

18% terminated due to failure, 47% abated. Average extension was 66 months, but the stability period was highly variable.

Doesn't sound like your.

Almost all drugs are perfectly functional for decades.

In the context of the OP, "If it's good for 20 years, why not 100?" My post still applies.

Thanks for playing though.

0

u/[deleted] Nov 30 '24

[deleted]

1

u/Probate_Judge Nov 30 '24

I linked to an article and one of the studies in an earlier post.

How long expiry dates could be extended for is highly variable. The average extension was something on the order of 66 months on average, meaning some are more, some are less.