If mold and bacteria need moisture to grow, how can sealed powdered food expire?

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Realized some vacuum sealed meal replacement powder had an expiration date, but I’m trying to see where the danger is. If it’s added to boiling water, and had no exposure to sunlight or moisture inbetween, where and how does the danger/expiration occur?

In: 16

That’s not what “expired” means. The company did a scientific test and will guarantee that if you eat it before that date it won’t be bad. After that date, they don’t have any scientific facts and the lawyers aren’t good with “probably safe”. The date tells you a lot about the test and only a little about the food.

**Don’t eat expired food, experimenting on yourself is not what I’m advocating.**

Mold and bacteria aren’t the only factor for spoilage on foods. They may absorb materials from their container that could make them unpleasant or unsafe, the chemicals in them may break down on their own or they might feel the packaging isn’t likely to last a very long time.

Some nutrients and substances just break down over time. In a snarky way if you wait long enough, EVERYTHING expires because of radioactive decay. It’s just “long enough” might be “millions of years”.

Some of this is related to liability. In theory yes: if a powdered food is kept absolutely sealed away from anything that could promote decay or growth of bad things, it is good forever. But how long until a plastic wrapper degrades or the metal in a can starts to leech? In some climates that could be as little as a couple of years, in others it could be decades.

If they put “never spoils” on the bag and you don’t notice that the plastic degrades enough to let air in at the 5-year-mark, then you get sick from 10-year-old powdered whatever, you could argue they made a false claim and potentially sue them. So it’s in their best interest to make some random guess that’s well within the expected life of the storage medium and argue that’s the cutoff. If you eat it after that period, it’s up to you to make sure it’s safe because they’ve told you it might not be. (It’s also reasonable to say you should inspect your long-term storage of supplies regularly for contamination!)

Also note a lot of times it says “best by” instead of “use by”. That usually indicates the concern is not so much spoilage as that the volatile compounds that make it taste good will have decayed and it won’t taste good. That’s not “dangerous” but might not be “pleasant”.

The true limit is the packaging. The expiration on military meals is when you need to inspect the packaging for failure. Properly refrigerated dried food can last for a decade. In a cool environment, 3-5 years, in an outdoor environment but shaded, a year. Out in the daily sun, a few months.

UV and thermal cycling degrades the packaging, that’s the practical limit on food safety.