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Coffee Q&A | Espresso, Bean Density, and Crema

Posted on April 17, 2013 by Venia Coffee Roasters | Keith There have been 0 comments

Q: I like to experiment with what coffee I use in my espresso maker.  I notice some coffees work really well, producing lots of crema, well while others are hard to grind (using my hand grinder), taste sour, and produce a thin espresso.  What is happening?

 

A: Experimenting with different coffees when making an espresso is a lot of fun.  I still remember the first time I tried a Brazil based espresso blend side-by-side with a natural processed Ethiopian Harrar.  It was a wow moment in my life when I realized how deliciously different coffees from around the world can be.

For understanding, espresso is a preparation method and roasters roast coffee specifically for the espresso preparation method. Say a roaster has a single origin lot of Ethiopia Harrar, for example.  A typical roast profile for a pourover (drip) will be lighter than one for espresso.  Using the lighter roast profile in an espresso will produce a very bright (sometimes sour / sometimes pleasant) and lemony cup, lacking the caramels, chocolate, toffee and body compared to the same bean roasted a bit darker for espresso.

Some coffee beans are more difficult to grind because of density.  Bean density is impacted by multiple factors, most common are plant variety (compare a Pacamara's soft bean structure to a Typica), growing altitude (generally higher is denser), and bean ripeness when harvested.  Processing, as far as I know, does not have a substantial effect on density (natural, washed, semi washed, etc...).

 

Coffee-Roast-Progression-Light-to-Dark

 

When roasting coffee, several things happen that affect bean density: the loss of water and the expansion of the woody structure of the bean.  Much of the expansion happens at the onset of first crack and continues through second.  Most palatable lighter roasts can end as early as the end of first crack where the beans are still relatively dense, while espresso roasts tend towards the onset of 2nd crack or beyond (of course it is a subjective choice).

As for crema production on an espresso extraction, again, many things affect this including those things mentioned above (variety, process, and roast degree).  Anecdotal-y, it seems natural and honey process coffees tend to have more crema than washed, but I could also point out hundreds of exceptions to that observation. Elapsed time after roast has a big impact on roast degree.  A huge decrease in crema is seen after around 14 days after roast.  A tasting attribute we call "body" increases through the roast spectrum until around 2nd crack and then it drops off.  I would speculate that there is a correlation between a coffee's body and the amount of crema produced in espresso, although I don't remember seeing any studies on this topic.

 

If you have a coffee question you want answered, send us an email and we will try to give you an answer.


This post was posted in Coffee Education and was tagged with Coffee, Coffee Roasting, Ethiopia, Ethiopian Coffee, Natural Processed Coffee, Washed Coffee, Espresso, Q&A, Coffee Density, Crema, Dark Vs. Light Roast

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