The external void space for coffee beans is probably something around 50%. So for a pint mason jar filled to the brim you'll still have about half a pint of air. A typical food vacuum will remove around 80% of this so the difference between filled to the brim and then 80% vacuumed and half filled and then vacuumed is not very large, and either is less air than a filled jar that has not been vacuumed.

But if simply "minimizing" air contact is good enough then why bother with a rigid jar or a vacuum in the first place? Why not just package the coffee in ordinary ziplock bags, wrapped with elastic or packed tightly in place so that they do not inflate with air?

jpender wrote: But if simply "minimizing" air contact is good enough then why bother with a rigid jar or a vacuum in the first place? Why not just package the coffee in ordinary ziplock bags, wrapped with elastic or packed tightly in place so that they do not inflate with air?

Precisely. Why not indeed.

Aside from personal choice and having a test to backup the validity of your choice you can read this thread (Mason jars versus zip lock bags for storage of roasted coffee) for another long discussion on the same subject. I believe it comes down to adequate storage techniques and I don't think there is a school of thought that thinks minimizing air using a ziplock bag is inadequate. It is very easy to fill a mason jar tightly and just screw on the lid without a worry about punctures. Having said that, I do like the idea of using an elastic if using a ziplock so the container changes in size with usage. I just never thought of that...