@DrHenley
I have a question. How long will an unopened can (metal can, plastic can) of ground coffee beans last? I've had a can on the shelf for almost two years now and I don't want to open it because the coffee in there isn't what I like, although I'd consider it a blessing if there was none of the good stuff left. So it's just sitting and I'm worried it'll go bad eventually. Do you have any experience with that?
"Bad" is relative. It's not going to kill you no matter how long it's been in the can as long as it's well sealed. It just tastes progressively worse. James Hoffman did some YT videos in which he drank coffee that was decades old out of curiosity. (video below).
Back in the dark ages before whole bean coffee was a "thing", I bought ground coffee for many years and paid attention to how it tasted when I first opened the package, and how the taste changed thereafter...whether it was a bag, a brick, or a can. The best was vacuum packed in a can with CO
2.
Whenever coffee is ground, oxygen comes into contact with the grounds. Even if they vacuum pack it after grinding, it has begun to oxidize already. Unless their grinder is in a pure CO
2 environment, which I doubt.
This is not true with whole bean coffee. After roasting, the beans give off gasses (mostly CO
2) for a few days. They package it while it is still offgassing in bags with one-way valves, and the gas that comes out of the beans purges most of the oxygen from the bags. Unless the ground coffee you buy is in that type of bag, it was not offgassing when it was bagged. Most ground coffee does not.
However, those "one way valves" aren't perfect and the do let some air in.
If vacuum packed in CO
2 immediately after grinding, you have a chance of the coffee lasting a good while in a controlled environment (no heat getting to it)
But there is no way I can quantify that.