When you open up a bag of coffee? pick up a small handful of beans. Are they glossy or matte in appearance?
As you roast a coffee you break down the cell structure of the bean, releasing CO2. When the CO2 comes into contact with oxygen, it creates a chemical reaction that leaves behind the oily or wet appearance that we can sometimes see on the bean.
Though oxidation is a natural process, and will happen over time with all coffees; the oily sheen will appear more quickly as the result of a high-heat and/or high-duration roast (typically used to achieve a dark roast). This is not a sign that the coffee seed was of a lower quality (but that it is either a darker roast or has been sitting on a shelf for a while.) These oils, like all oils, have the potential to go rancid over time, causing a sour flavor in your coffee, but that could take a while.
At Progeny we’re committed to showcasing the best single origin, micro-lot, coffees from Colombia. Coffees which have been roasted perfectly to showcase their balance while highlighting what makes each coffee unique. We find that this is usually achieved by a light to medium roast. This means that most of our coffees will arrive at your home without an oily sheen on our beans.