What It Means If Your Coffee Beans Have A Wet Or Oily Sheen

For those of you who grind your own coffee, you've probably noticed that sometimes the little roasted bean halves can have a slightly shiny or, for lack of a better word, "wet" look to them. First off, that sheen is perfectly fine, and it's actually to be expected. What looks like dampness is actually natural oil from the coffee beans, which can weep out to the surface during the roasting process.

That oil you see is a significant part of why coffee smells and tastes the way it does. And if you notice carefully, you'll find that darker roasts tend to sport that oily coating more often than light ones do, because the longer the beans have been roasted, the more that oil is drawn out. 

That being said, if you have a lighter roast bean whose appearance is oily, there's a possibility that those beans have been sitting in storage for a while. In those cases, you might already have a stale batch, which means the resulting cup of coffee isn't going to be as full-flavored as it should have been.

If you've got an oily batch of beans, you'll want to pay extra attention to cleaning your equipment. That oil can cause additional caked-on buildup that drier beans wouldn't, so a more frequent wipe down of your grinder is recommended after processing them. If you happen to be lucky enough to own a super automatic espresso machine (lucky you!), which are those high-tech coffee makers that grind whole beans and brew complex espresso drinks with the touch of a button, you'll want to avoid oily beans altogether. 

Manufacturers warn against them because they can gunk up the burrs and gears within, and considering these types of machines can cost well into the thousands of dollars, you don't want to risk losing the money you spent on something like that. 

Instead, you'll want to find an alternate way to brew with those beans (a French Press, would do nicely), or at the very least, grind them externally, then brew them with the automatic espresso maker, which is always an option. That way you can at least wipe down your standalone grinder rather than risking the native one on your super automatic device. For those of us who don't own one, brewing a perfect cup at home is achievable using regular equipment, however, as long as you follow some of these tips.