I think I know what you're talking about. I used to really like Tchibo
coffee and a few months back I bought some and it had this weird taste
which I would describe as similar to gypsum (dry wall dust).
These days I buy fresh roasted beans from local roasters or online and
grind it at home. Much better quality and taste than preground.
--
Adam Mickiewicz on coffee:
https://www.youtube.com/watch?v=3J-L5mRoc6c
"Coffee is a great power in my life... it chases away sleep, and it
gives us the capacity in engage a little longer in the exercise of our
intellects."
- Honoré de Balzac