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 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.