Three weeks back I dumped a quarter cup of rice through my old Capresso and the next morning my Sumatran beans tasted like someone washed the mud off them. That same bag had been giving me this dull, heavy cup for a week, kind of like drinking dirt water, then suddenly it was all bright and clean with a weird citrus pop I never tracked before. I was honestly pissed at first because I thought the rice messed up my machine, but turns out it just stripped all the stale junk that was choking the flavor. The difference was so huge I ran a second batch of rice through just to see if it changed again, and it didn't, so it was definitely the cleaning. Now I do it every month or so and my beans always taste fresher, even the cheap grocery store stuff.