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Coffee Color Spectrum: How Roast Levels Affects Taste

Good morning, coffee students! We hope you're all having a great summer filled with late nights full of Dizzy Three (if you’re old enough) and early mornings full of Ready-to-Drink Cold Brew. But learning is never over, even if the school year is. And today we're going to learn about the coffee color spectrum!

Here at The Roasterie, we love giving our coffee students lessons about the wonderful coffee bean.  But before we swan dive into today’s lesson, let’s set something straight: Coffee beans aren’t beans; they’re seeds. We call them beans because a long time ago, people would see stuff and just call it what it looked like. The “bean” category just stuck and ever since, people have been too busy drinking the stuff to ever stop and vote on a proper name change. The coffee color spectrum is a range of colors that coffee beans turn to as they're roasted. It is usually a good indicator of the flavors you should expect when you buy a bag of coffee! 


Image Source: Sweet Maria’s Coffee Library

As you may remember from our previous lessons, raw coffee “beans” are green; roasted beans range from light brown to dark brown to black. That’s why roasted beans make the brown coffee we all know and love! A coffee bean’s final color before it is ground is dependent on when we decide to stop the air roasting process. The color of coffee is directly related to its roast level.  As a general rule, the darker a coffee bean is, the longer it was roasted. That’s because the natural sucrose (sugar) within the bean goes from sweet to caramel to burnt as it goes through the roasting process. Ready to go more in-depth in the coffee color spectrum? Let’s dive in.
  1. Green unroasted coffee
    • Raw
    • Room temperature coffee
    • Sweet and fruity
  2. Starting to pale
    • A lighter green
    • About 275 degrees
    • If it were steak, it’d be really rare
  3. Early yellow
    • Lime yellow in color
    • 330 degrees, give or take
    • Moisture from the beans starts to steam off
  4. Yellow-tan
    • Golden in color
    • About 345 degrees
    • Starts to give off a toasted bread fragrance
  5. Light brown
    • Slightly darker than a pair of khaki chinos
    • 370 degrees, almost at the important first crack
    • The coffee starts to shed its chaff
  6. Brown
    • Knocking on the door of the first crack
    • The sucrose starts to brown (the Maillard reaction is really responsible)
  7. 1st crack!
    • Color hasn’t changed much
    • The beans sound like a bowl of Rice Krispies, only louder and better
    • As a result, beans start to increase in size and release carbon dioxide
  8. Middle of 1st crack
    • The bean starts to climb towards an internal temperature of 370 degrees (this is critical because this is the melting point of sucrose)
  9. 1st crack finishes
    • Beans reach what is known as a city roast
    • The beans are now considered “coffee”
  10. City +
    • A more dark brown
    • On the cusp of a light French roast
    • Starts eyeing the 2nd crack
  11. Full city
    • AKA a light French roast
    • The bean has swelled considerably since roasting started due to the release of CO2
  12. Full City+
    • Resembles a lighter dark chocolate
    • At this point we start to hear some soft snaps; the 2nd crack begins
  13. Vienna- light French roast
    • Darker in color
    • The origin flavor begins to be overtaken by the roasting characteristics
  14. Full French
    • The bean starts to blacken
    • Sucrose is heavily caramelized
    • This is dangerous territory, as beans can burn very quickly
  15. Fully carbonized
    • Looks like black licorice
    • The beans start to become charcoal
    • Open a window because there is probably a lot of smoke!
  16. Imminent fire
    • Piano black in color and shine
    • Get the fire extinguisher ready!

How can you tell what roast a coffee bean is?

But how do we know what color indicates what roast style a bean is? Lucky for you, we’ve been doing this for a long time so we can look at a bean and identify its roast in the blink of an eye.   We also have what’s called an Agtron machine to help us make faster (and maybe even a little more accurate) identifications. An Agtron machine reflects near-infrared light on a sample of coffee to analyze and assign a number to the beans' roast color. The larger the number, the lighter the roast.  We have found certain numbers that match our taste preferences, and then we use the machine to get as close to perfection as we possibly can. 

Why does the coffee bean color matter?

The key to roasting great coffee is consistency, which is why we use the air roasting process. This process allows us to control the temperature precisely and roast each individual bean consistently as it floats on the fluid bed.  But we wouldn’t be able to replicate our perfect roasts time and time again if we didn’t do countless trial and error, of which we would have had extreme difficulty if we didn’t have our trusty Agtron!  So what’s the true lesson here kids? If you’re going to roast your own beans, invest in an Agtron!   Want to see our Agtron up close and personal? Come see us on a tour!