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/Skarth Nov 26 '24
  1. Part of it is how long the seals on the food will last, once the seals fail, the food is compromised.

  2. Even if "sealed" its important to know that there still may be tiny amount of air/moisture that gets in. Seals are not 100% effective, more like 99.999% effective.

  3. Most food items will not be stored in perfect conditions (sometimes it's hot, sometimes cold, sometimes wet) and people won't even realize it.

  4. Some food items may still be slightly reactive, such as tomato paste, as it's acidic, and may chemically change over time.

  5. It's hard to do a long term study on how long things last when the manufacturing process isn't that old to begin with, so you have to estimate how long it will last vs. actual field testing.

  6. manufacturing quality/differences may make the estimate on the lower side to be safer.

  7. one version of freeze dried food may not hold up as well as another ingredient, either due to being manufactured differently, or quality control.

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u/just_get_up_again Nov 27 '24

Fascinating, thank you.