Coffee Roasting: Shorting the Color Spread
Like many things in life, consistency is important. There is nothing more disappointing than going to your favorite restaurant and getting your favorite meal and it’s just not up to par with your visit.
Well, the same is true in coffee. While taste and aromatics are key factors in our roast profiling, consistency is crucially important as well. Keep in mind this is an organic product. The coffee bean is actual the seed of the coffee cherry and, prior to processing, is still alive. Add to that fact, that we are human, you have a recipe designed for inconsistency not the consistency we all desire.
As the coffee roaster, there are many variables outside of our control. However, much of what is good or bad about coffee is contingent on the roast. So it has been our endeavor to not only provide an enjoyable cup of coffee, but just as important as taste, is the ability to deliver that same experience over and over again.
In science, repeatibility is the foundation for the scientific model. With over 100 data points that we collect on each roast and any number of variables from temperature, humidity, and other roast conditions, including differentials in the coffee from crop to crop, we try to apply those scientific concepts and principles to our coffee profiling. Each roast profile is designed to keep taste and other sensory experiences in mind, while we also what to design the roasting profile of each coffee for consistency.
If things are repeatable in our roast process, then we can reproduce a coffee just like the previous bag of Mavericks you bought or the last cup of Mavericks your drank. One factor that we have to focus on it our roast is the color spread. Coffee beans are roasted primarily with conductive and convective heat, while radiant heat can be factor, conduction and convective heating are the primary areas of focus.
For more information on these two methods of heat exchange, you can see our article here. In layman's terms, conductive heat roasts the coffee from the from the outside of the coffee bean inward and convective heat roasts the coffee from the inside of the coffee bean outward. When I am referring to the spread, I mean the difference in the coffee beans color after it has been roasted between the inside and the outside of the bean.
For a coffee roaster, you cannot visual see the coffee beans’ inside color until after the roast, so this like other quality control processes, such as cupping, is after the coffee has been roasted. This post-roast analysis, can be very instructive. To measure the spread in color from the outside to the inside of the roasted coffee bean, we simply grind a sample of coffee beans and compare the color of the whole beans coffee with the color of the ground coffee.
In basic terms, the wider the differential between the whole bean and ground coffee the less uniform the coffee bean developed during the roast. A wider spread would mean that while a coffee bean might look very developed on the outside based on the beans appearance, on the inside, the coffee might be underdeveloped or not developed to the same point as the outside of the bean.
The wider this spread is between the outside and inside color, the more dissimilar the application of conductive and convective heat in the profile.
It has been our observation and our experience that by “tightening the spread”, which is minimizing the difference between the inside and outside roast colors, we can improve the taste and provide a coffee that is more consistent from batch to batch.