Espresso beans: Oily or dry - which is best?

Discuss flavors, brew temperatures, blending, and cupping notes.
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Postby Tod » Aug 09, 2008, 4:57 pm

I have been using beans that were roasted daily by a roaster/coffee shop. The coffee and espresso she served was always top-notch. The beans she sold were always oily, which she stated was the only way you could get some of the subtle flavors in a brew, whether coffee or espresso.

Then I bought a Gaggia Synchrony and it had fits with the oily beans. The delivery system from the built-in grinder to the filter would get clogged with the grind. Tech Support at the place where I bought it told me that was because the beans were too oily. My friend at the coffee shop said "nuts" when i told her. She told me that if I wanted dry, go to the supermarket. But the brew wouldn't taste half as good as she made. An experiment bore her out - the brew from dry (and probably months old) whole beans was terrible. I finally convinced the reseller that the machine was defective (since there were no pre-sale caveats about not using oily beans) and I got most of my money back.

So what's the opinion on this board? Oily or dry for espresso?


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Randy G.
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Postby Randy G. » Aug 09, 2008, 6:06 pm

I have had beans that were oily and were good, but in my experience oily beans are one indication of over-roasting, poor storage, or age.

For example, I will soon be posting a review of some excellent Kona I roasted at home. The pictures of the beans were taken at about 4 days after roasting and the beans were showing spots of oil. If they had been sitting for about another four or five days they would have been oil-covered, but at that point they would have been about at the end of their useful life (IMO) for espresso... maybe a few days left for drip.

Beans stored in a hot roastery, shipped in the back of a hot truck, and stored n a hot storage room at a coffee shop will also become oily far faster than beans stored in a cool place.

Low quality beans are often over-roasted to a dark, oily state because it is the only way to burn off their natural flavor so that they become drinkable (Vietnamese Robusta comes to mind- there you get your choice of a rubber taste, or a burnt rubber taste).

So, generally, both of your sources are generally correct, but you cannot take "oily is bad" as a rule— much like the "Golden Rule," it is a guideline.
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Postby another_jim » Aug 09, 2008, 6:18 pm

Beans get oily when they have been roasted beyond the point where the cell walls rupture and the oils stored inside the cell wall vacuoles are released. This stage, while roasting, is roughly marked by a crackling noise called the 2nd crack (the first crack happens at a lower temperature when the water turns to steam).

If the roast is very dark, so the beans are a dark chocolate color or darker, the oil will be on the bean from the day of the roast and stay there until it is about 3 to 4 weeks old, at which point it will all have evaporated. The sight of beans this color without oil is a warning that the coffee is stale. If the roast is a bit lighter, milk chocolate color, the oil will take about 3 days to a week to appear on the bean surface. In some parts of Europe, which like this level of roast, the saying is that a bean without oil is either too old or too young. Beans lighter than milk chocolate have intact cell walls and will never get oily, and that will not be a clue about freshness or otherwise.

So much for the facts, what about the taste?

Advocates of lighter, oil-free roasts claim oily beans taste rancid. Advocates of oiled roasts say that without them appearing through roasting, the oils cannot get into the cup, since grinding alone leaves most cell walls intact. There is a bit of truth to both these statements, and in terms of the flavors in the coffee oils, a medium, milk chocolate roast, fairly new, and just showing a few spots of oil, will taste the best.

However, not all things are equal. The darker one roasts, the more one roasts out the fruit and floral flavors in the coffee. On the other hand, very dark roasts have spice and smoke flavors that many people enjoy. These flavors have nothing to do with the oils.

Finally, among people who make a hobby of espresso, you will probably find nobody who will willingly drink a coffee whose beans are so oily that they foul the grinder. I hesitate to say that roasts this dark are the Thunderbird or peppermint schnaps of coffee, but it wouldn't be an entirely unfair statement.

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Postby Tod » Aug 09, 2008, 8:09 pm

@ RandyG: Thanks for your comments and clarifications.

@Another_Jim: Your explanation is just about the best I have ever heard or read in terms of the processing and tasting.

The beans I purchased were from the same container that Sophia (the owner and roaster) stores her beans for on-site grinding and brewing. She always grinds freshly before making a cup of espresso. Her grinder, to my knowledge, has never fouled. The grinder built in to my Briel has never fouled. In the case of the Gaggia I am certain that the problem lay in the "transport" mechanism from the grinder to the filter as that is where I found the mess when I cleaned the unit (several times). I worked in several European cities and our team rented apartments from time to time. The locals when we were in Madris and Barcelona always brought over roasted beans for our standard drip coffeemakers and they were fairly oily. But I never knew how fresh they were but I do know that the drip coffee was always good (and compared favorably to espressos at coffee bars) even though we were using an el cheapo blade "grinder" (which I always think of being nothing more than a spice grinder).

Thanks for the responses!


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Postby cafeIKE » Aug 10, 2008, 2:49 pm

Tod wrote: el cheapo blade "grinder" (which I always think of being nothing more than a spice grinder).

Just FYI, no self-respecting chef uses a blade grinder. Depending on the spice and the dish, it's either a mortar and pestle or a ceramic mill.

A blade grinder is a POS, regardless of what gets whacked therein!