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Coffee & Roasting

Dark roast, light roast, oily, caffeine levels, antioxidants, bitter, strong….aaaah, what does it all mean!?

There is a whole subset of espresso drink related terminology that we are not going to discuss.  As Silver City’s specialty coffee roaster, our focus is on roasting and cupping.  This post is going to look at roast degree and a few other properties that respond to different roast levels.

Roast Degree

Light Roast
Sight:  Splotchy, light brown, very slight expansion (generally smaller)
Taste:  Bright, light body

Medium Roast
Sight:  Even, medium brown, moderate expansion
Taste:  Balanced, full body

Dark Roast
Sight:  Dark, oily, full expansion
Taste:  Bitter, thin body

These are broad descriptors based on a very generalized roast degree.  However, the nature of the green coffee bean plays a huge role in how it responds in the roaster and what ends up as the cup characteristics.  For example, a bean with high moisture content taken to the same temperature (and therefore same roast degree) as one with a lower moisture content, can end up tasting and looking lighter.  This is because it is less responsive to the heat of the roaster.

Additionally, in terms of body (a quality many people assume is 100% controlled by how dark the bean is roasted), roast degree is only part of the equation.  Two different beans taken to the same final roast temperature can end up with completely different bodies.  Furthermore, the brew method plays a big role in perceived body.

Chemical Properties that Change with Roast Degree

Oil on the beans
We want to address this first because a lot of people are unaware of a little dirty secret.  Yes, darker roasted (actually – ‘overroasted’ ie burnt) coffee is oilier.  However, OLD coffee is also oilier. And once the oil is on the surface of the bean, it is more prone to going rancid.  Fresh roasted coffee that is not burnt should be consumed with 1-2 weeks after it has rested (and may never reach the point of looking oily).  Oily beans are often poorly roasted coffee and/or old.

Note:  In contrast to that description, beans that have been decaffeinated can end up looking oily after roasting (and not be burnt or old).

Antioxidants
Antioxidants are substances that inhibit the oxidation of other molecules and may prevent or delay some types of cell damage.  You can find antioxidants in both food and beverages.  Coffee is not the most antioxidant-rich food available but because people do not generally consume large amounts of berries, it is often the source of the majority of one’s antioxidant consumption (see chart below).  So what happens to antioxidants over the course of the roast?

As we pointed out in our post on Fresh Roasted Coffee, the darker the roast, the fewer the chlorogenic acids (CGAs), which are a known to be biological antioxidants.  This graphic says it best –

The darker the roast, the fewer the antioxidants. (For more info, see http://www.scaa.org/chronicle/2014/07/11/coffee-roasting-chemistry-chlorogenic-acids/)
The darker the roast, the fewer the antioxidants. (For more info, see http://www.scaa.org/chronicle/2014/07/11/coffee-roasting-chemistry-chlorogenic-acids/)


Also, in case you’re curious –

Antioxidant amount based on food

Caffeine Content and Roast Degree
We get asked this question a lot in the drive-through in Silver City!  Which bean has the most caffeine?  Give me your darkest, most caffeinated bean!!  Or even more imprecise – Which coffee is your boldest?

We are not always certain whether the people who ask for ‘strong’ or ‘bold’ coffee are looking for caffeine or a stronger coffee flavor. When we ask, many people say “both” – as in, give me something with lots of caffeine and that tastes like coffee.  Since we are all about the taste of coffees here and don’t water anything down (at least 20 grams of coffee/12 oz water), a ‘bold’ cup refers to everything.  Caffeine – that’s a different story.

Yes, roasting dark causes degradation of the caffeine molecule.  But in reality, that change does not happen until the bean is roasted really dark.  To be precise, over the course of the roasting process, “Caffeine did not undergo significant degradation with only 5.4% being lost under severe roasting.” (Trugo & Macrae).

A much bigger player in caffeine content is the bean varietal.  Some are bursting at the seams with caffeine (often times descendants of the unsavory Robusta species) and others will have less.  Because Silver City is a friendly city, we receive great feedback from our regulars about how the coffee makes them feel.  The black coffee drinkers who travel the world (on our coffee map) are the most reliable because they aren’t under the influence of sugar and they’ve tried everything.  But we take comments from everybody.  Once enough people say something like, “Wow, that Costa Rica really gave me a buzz,” we know that that particular bean varietal likely contains more caffeine and we know to encourage or discourage others accordingly.

Bitter Beans
[Good] coffee should not taste bitter and should not be a menu option.  Another common request is “the least bitter coffee bean.”

“Bitter” can be the result of bad beans (under ripe, over ripe, moldy, tainted etc.), bad roasting or over-extraction when brewing.  We sometimes hear people describe our really bright coffees (such as the brilliant, grapefruit explosion Kenya we had at one point) as bitter but they’re confusing the two terms.  Bitter is sharp, pungent, offensive – like moldy bread.  Brightness can occasionally be overbearing – like, say, in grapefruit juice – but even then, it should not be revoltingly offensive.  Often, roasting a little bit darker can temper a really bright tasting coffee.

Roasting to Serve

As the only coffee roaster in Silver City limits, we strive to serve the most amazing coffee available locally.  Being a small operation and roasting in small batches gives us a great deal of flexibility.  Those willing to purchase a whole batch are welcome to ask for a custom roast.  Everything on our Silver City drive-through window and listed on our online store is roasted somewhere from a light to a medium-dark level – depending entirely on which roast level best represents a given bean.

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