Deb M., of Charlotte, N asks, “What makes some coffee beans oily and others dry in appearance?”

You open up your bag of freshly roasted coffee beans, scoop out some, and then notice they're bright with an oily residue. Is this a good or bad thing? What should fresh roasted coffee beans look like?

First and foremost, they should look, smell, and taste FRESH. Nothing makes a worse cup of coffee than stale beans. Some of the tests for freshness are vibrant fragrance that's a little peppery, a little sweet, an intensely deep coffee essence.

Next, the beans should be as uniform as possible, with no burnt edges, no ugly cracks or bits scattered throughout the bag, and no half beans (broken literally at the crack that appears naturally in a coffee bean). Oh, yes, they should be a deep chocolatey brown (for most beans from Indonesia through the Americas), and a mellow softer brown (for Yemen and Ethiopian beans and, often, for Kona and Jamaicans).

As for the oily appearance, on fresh beans that is more of an indication of the roast than the country of origin or any other factor. For example, the lighter the roast means that the beans are finished roasting before any oil appears on the bean; so their rather matte-like finish indicates both the lighter roast and, quite often, a light acidic taste. Darker roasts (French/Italian/Vienna) occur with various stages of the oils seeping out to coat the surface of the beans naturally. The oil actually seeps out in stages, first a few dots, then some blotches or splotches, and then finally an overall glossy sheen all over the bean.

Coffeol or the oil that occurs naturally in coffee beans is about 15% in the green bean. After roasting, the oil is released because the bean becomes porous.

These are sometimes referred to as "volatile" oils and do contribute to the taste, albeit a subtlety of the coffee, and filtering, especially through paper filters, eliminates most of this oily residue, something viewed as undesirable by some coffee fans who believe that the oils contribute considerably to the final taste of the cup.

An oily appearance may have another root cause and that's flavoring oils added to the bean after roasting to infuse the coffee beans with the essence of vanilla, cinnamon, chocolate and a whole host of other flavors. When buying these flavored coffees, buy in small quantities, keep them tightly packaged (even more than your usual beans), and use promptly as there is more possibility for rancidity.

Do you have a question? Send me an email at Phil@SupermarketGuru.com. If we use your question we will send you an extra large SupermarketGuru.com canvas tote bag and autographed copy of my book, Healthy, Wealthy & Wise!