Or, at least when your food was packaged and sealed?
I think that commercial aircraft are pressurized to 8,000 foot level when actually much higher, but clearly a lower pressure than sea level. I recall back when I did fly and you either got a bag of something like chips or pretzels for 'free' or bought one, the little bags were blown up light air pillows.
Today I was going to make a quick cup of coffee and turned on the Keurig machine we have in the corner. I had recently bought a box of the flavor we like, and got one out. The top was sort of sucked in a bit. Coffee was very good, but I recall usually seeing the top seal of aluminum foil puffed out, as if processed and sealed at a lower altitude.
The coffee, of course, is stored and brewed at a constant altitude, but I'm thinking after looking at the whole box that all were sealed at the same time (slightly sucked in) and peaked at another box from another purchase and there was the slight pillowing of the top of the container, so it wouldn't be subject to the extreme altitude changes that I noticed with the airplane cabin.
Are there any other packaging expansions that I've not paid enough attention to in order to notice this effect?
Just curious.
Dale