title_body: How quickly does ground coffee get stale?
upvoted_answer: I can say, by experience, that it's not a superstition. Maybe not seconds, but for sure it's just a few minutes.
  
  Maybe someone could find a reference to an experiment or I may encounter and add it later. But, you can easily observe it by your nose.
  
  The aromatic components are the source of the flavor in coffee beans. When you ground them, you crack them fine. The components get free and start to evaporate. That's why you can smell them. However, we want to taste them so badly. So, we need to trap then into the water as quick as possible, before most of them evaporate.
  
  
  
  Below is a nice chart that shows how quickly coffee goes stale when it's stored as whole beans. Ground coffee, I assume, would be similar, but so much quicker as the surface area is greater for evaporation this time.
  
  When does coffee go off?