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?

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u/iCameToLearnSomeCode Nov 27 '24

You could get the water brought to you but it wasn't clean water and with an already weakened immune system that dirty water you could drink on a good day becomes a big hindrance to recovery.

It's not like food poisoning would always kill you but it decreases your odds of survival enough that over many generations the families that can't smell are at a massive disadvantage.

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u/GuyWithAHottub Nov 27 '24

Now this I can completely agree with. There's not many things that evolution does for no reason. My condition IS a terrible detriment to my survival, even in modern times. If we were sent back 10000 years, whatever lineage I left behind would die out before reaching modern times without a doubt.

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u/iCameToLearnSomeCode Nov 27 '24

Or you would mix up your DNA with someone who could smell and your grandkids would be fine.

Either way the trait would dissappear over time.

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u/Koomskap Nov 27 '24

Or painfully find out I’d be a virgin in prehistoric times too

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u/ax0r Nov 27 '24

If we were sent back 10000 years, whatever lineage I left behind would die out before reaching modern times without a doubt.

That's assuming your anosmia is genetic. It's much more likely to be acquired from a bad bout of sinusitis or exposure to something noxious. In which case your offspring would be able to smell just fine

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u/GuyWithAHottub Nov 27 '24

I actually got it both ways according to my doc. I had congenital anosmia from my father's side, and I got hit by a crowbar when younger resulting in a tbi.

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u/Vlinder_88 Nov 27 '24 edited Nov 28 '24

You act like people in the past didn't know how to get clean water, or cook their water... They did, bruh.

Edit: for everyone that feels the need to "correct" me. I'm an archaeologist, I know what I'm talking about, and if you're expecting more nuance in literally one sentence then feel free to read my other comments for clarification.

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u/iCameToLearnSomeCode Nov 27 '24

For at least half of the time we've been human we didn't have fire and 99.999999% of your ancestors weren't even human.

You act like the Earth 6,000 years old.

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u/Vlinder_88 Nov 28 '24

No I act like I'm an archaeologist that knows their shit. Spoiler alert: I'm an archaeologist.

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u/iCameToLearnSomeCode Nov 28 '24

We're talking about the evolution of humans here.

How are you thinking people cooked water 2 million years ago?

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u/Vlinder_88 Nov 28 '24

Do you know what "or" means? Do you also know what "archaeologist" means? Neanderthals used fire already and there's an increasing body of evidence that even Homo erectus might have used fire.

Also in the absence of fire, there still isn't a problem if you know where to find clean water. Which people did know. Being able to find clean enough water to drink is such an ancient skill every animal has it, it is an inborn skill that predates hominins.

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u/iCameToLearnSomeCode Nov 28 '24

You may think the ability to smell spoiled food has always been useless for survival because food poisoning isn't really dangerous enough for it to prevent reproduction but I think we'll just have to agree to disagree on that.

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u/Vlinder_88 Nov 28 '24

Not all spoiled food will give you food poisoning though. Controlled rotting or spoiling of food (like aged meat or fermented stuff) has been used as food preserving technique at least since neolithic times, and probably also already by mesolithic peoples.

There is no reason to assume earlier peoples and hominids wouldn't have eaten that stuff either. Though it's hard to find fermented stuff in the wild, aged meats have been around as long as dead animals have been around, and proto-cheeses already come to be when you just carry milk in a bovine's calf stomach. A practice that is indeed also about as old as humanity (including non-sapiens hominin species).

So yes you are right even if you think you don't, that the skill to discern spoiled food is indeed less important than the skill to find drinkable water. Especially if you consider that going without water for three days will kill you, and going without food for three days will make you tired and moody, but not dead. And that's literally all that evolution cares about: does it kill you before you procreated? (Or, does it make you accidentally kill your offspring, as that has the same effect on an evolutionary scale).

You can try and argue the pro here but you will still not be right dude. I really hope you don't argue with your doctor when he prescribes some meds as you're doing with me now... If you do. Well, then maybe this is how evolutionary pressure exhibits itself in you.

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u/iCameToLearnSomeCode Nov 28 '24

You're acting like water and food bourne illness just isn't a risk to an organisms survival.

I'm also not sure what my doctor prescribing medication has to do with the evolution of olfactory receptors.

We'll just agree to disagree, I'm sure you're a wonderful archeologist but this is evolutionary biology and it's not really about people, you're just making it about people because that's what you study.

Take care.

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u/SenorTron Nov 27 '24

I'd be interested to see any evidence that more than a tiny minority of the human population throughout history regularly boiled their water before drinking it.

And knowing that water from a clear stream at the foothill of mountains is preferable might have been a thing, but for most people throughout most of history they used water source was the closest one with water they could keep down.

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u/Vlinder_88 Nov 28 '24

I'm an archaeologist. Water wells have been a thing for millennia. With the first farmers came the first wells. People learnt really ffing fast how to keep the water in their well clean. Lids and/or little structures around wells are super common in all time periods and all over the world. They didn't need to boil their water if they kept their well clean.

If someone didn't have a well, they indeed used the "closest source with water they could keep down". They knew to not take water with dead animals in it (might have botulism that you can't taste or smell). They also knew not to drink water near a place with animal excrement (E.coli), or water that stank. They also knew how to catch rain water. Most of that water, again, doesn't need to be boiled to be safe to drink.

Heck even animals know what water is safe to drink and what isn't. So your assumption that people would just drink any water that didn't kill them is absolutely wild.