Oily Beans, Oily Coffee - Beans - Coffee Forum

kibblesplace said:

Why is it that when I open a package of whole beans, sometimes they are oily and other times they are completely dry.  I purchase all types of coffee, some are flavored, some are not.  Even after it's brewed, the oily beans will make an oily coffee.  You can see a layer of oil floating in my cup.

Judy, there are two primary explanations as to why some coffees have an oily surface and some have a dry surface and you hint at one of the reasons in your question.  Some flavored coffees (vanilla, cinnamon, chocolate, etc.) are infused with flavor by use of flavored oils.  Use of these flavor oils on normal coffees can result in the beans becoming "oily." 

A second reason relates simply to how long, or rather to how dark, the coffee is roasted.  The really darkly roasted coffees are roasted to a point that the physical structure of the coffee bean begins to break down.  As the structure of the bean breaks down it releases oils that exist in the bean naturally.  Coffee beans contain about 15% oils naturally and those oils contribute greatly to the flavor profile and the nuances you taste in that cup of coffee you brew.  When coffee is roasted very dark and these oils are released in the roast rather than in the grinding and brewing process you lose most of those flavor nuances.  That is why what type of coffee it is matters less and less as the coffee is roasted darker and darker — those subtle flavor oils are "cooked-off" and the coffee just tastes darkly roasted.

I hope this helps, but if you still have questions please post them.