Why does cinnamon in the grounds make older coffee taste better? If I go to make coffee and find that the coffee is a little old, I'll sprinkle a little ground cinnamon in the grounds in the basket before brewing. I won't use enough cinnamon that you can actually taste it in the coffee, but it seems to cut the acidity and bitterness. 

Does anyone know why this works? Is there anything other than cinnamon I can do this with?
I would say that the cinnamon restores some of those floral top-notes that have likely evaporated from older ground coffee, and hides some of the mustier, oxidized flavors.