I had a conversation the other day about the oiliness of coffee. My mother was saying that she tends to go for the shinier coffee because it is clearly more fresh and oily. This means she’s looking at the beans and choosing to go for the “wetter”, shinier looking beans because she wants freshness and quality. But should coffee be oily or dry? Which is better?

Oil greatly affects the flavor, so you want to protect it. Air will make it oxidate and go rancid. Therefore, oily beans are leaking their “goodness”; you want their outsides dry and insides oily.

Myth 1: Shiny beans are fresher; dry beans are dried out

Generally, through the roasting process, the shell of the bean will crack because the liquids and gasses expand, needing somewhere to go. This is normally carbon dioxide (CO2) and water turning to steam. However, the longer the bean is roasted, the weaker the shell is, and the more the oil will leak out. 

The oil on the outside comes from somewhere – the inside of the bean!

That means that the oil that would otherwise be preserved is now sitting completely exposed to the air, resulting in a drier, less flavorful bean and a shorter shelf-life.

Light roasts tend to be better in this area, as they will be less likely to leak the oil as quickly.

Make no mistake: the oil will eventually find its way out; the vast majority of beans crack through the roasting process. It’s just a matter of speed. But in general, oily beans means they’re closer to expiring.

Myth 2: A Good Dark Roast/Espresso blend should be oily

Once again, darker roasts are more likely to leak oil because their outer shell weakens and is more likely to crack wider due to a buildup of internal pressures.

However, there are some beans that have tougher shells and are more resistant to cracking so quickly, which means they are more well-suited for darker roasts.

One such example I’ve read is that old Starbucks favorite, Sumatran coffee. Apparently, the beans from this region of Indonesia are more robust.

But no, again, you don’t necessarily want them to be oily – it’s not a prerequisite. Some roasters seem to argue that you can make a dark roast that isn’t oily from the jump. They claim it’s a matter of roasting skill. I guess there’s room for debate.

Others believe that the darkest of roasts will be oily from the time they’re roasted onward. Some have pointed out that ultra-dark, dry beans have likely expired because that level of roast has almost certainly leaked oil. The lack of sheen indicates it’s evaporated away.

Europeans tend to like medium roasts, so they have a saying for that level of roast: dry beans are either too old or too young.

Myth 3: Oily Dark Roasts are Required for a Bold Brew

Darker roasts are more likely to be oily due to the roasting process, and some believe the oily exterior is essential. As I mentioned, some roasters claim that a “properly” roasted dark coffee won’t have that sheen for a few weeks after roasting. Others believe a dry, dark roast means it’s already expired.

Why do people like dark roasts?

It’s often because they like their coffee with a bolder, punchier flavor. However, dark roasts can lose some of the nuance that comes with lighter roasts. Through the extra roasting, they can often burn away some of the components that give it that little bit extra, that oil included, while caramelizing some of the sugars.

And it is for this reason that poorer quality coffee will most likely appear on shelves as dark roasts. It covers up the lack in the quality of the bean. This is not to say that dark = low quality, but it will sometimes hold true.

Bear in mind that the roast is not the only way that roasts can get bolder. The method for brewing is an important factor in how the flavor comes out.

For dark roasts, they’re inevitably going to be bold. But for light roasts, you have the option to brew for longer or to use a finer grind level. These will increase the amount of extraction and will pull out some of the more bitter flavors so that your coffee will be bold enough to punch you in the face.

Alternatively, you could use a higher ratio of coffee to water with light roasts.

In my opinion, lighter roasts have more versatility and have a longer shelf life, so I tend to gravitate toward them.

Myth 4: Dark Roast Beans are Naturally Oilier

This just seems silly. The argument is that darker roasts are oilier on the outside simply because they contain more oil to start. 

First, how do the roasters know the inner contents of the beans? I’ve never heard of them cracking them open to measure the average oil content.

Second, how would roasting it somehow conjure up a deeper well of oil?

Nah, I’m not buying this.

TL;DR

• Light- and medium-roasted beans tend to be oily as a bi-product of over-roasting, poor storage, or age.
• Dark roasts tend to be oilier because the bean’s shell gets weaker from longer exposure to heat. This leads to more oil escaping and oxidizing from the time of roasting.
• Oil is a major component in a coffee’s flavor, which means that the more you lose, the more flavor you’re wasting.
• Poor quality beans tend to be disguised through longer roasting times.
• Darker roasts do not contain more oil
• Dark roasts will commonly be oily due to the roasting process; some roasters claim this can be avoided.
• It seems widely believed that a very dark, dry bean is expired. Best to avoid.

One Last Note

I read on some message boards that people found that oily beans clumped and clogged up their grinder. This should never happen, but if it does, you may want to consider tossing the batch.