This is a guest post from a My Coffee Pub member and friend Kane Holbrook. Kane is a micro entrepreneur living in Louisville, KY. He has been in the coffee industry since 2005, working as a barista, roaster and now offers consulting services. He is the author of www.CoffeeSuplex.com.
I have been a member of My Coffee Pub for almost a year now. The thing I like most about the subscription is the experimental element that is inherent to the service. Receiving coffees from different roasters across the country, each month, serves to increase my exposure to the greater specialty coffee culture as a whole. This is important. It’s important because coffee is the most complex culinary beverage that we know of today. There are over 1000 volatile organic compounds in coffee that contribute to its overall flavor profile and we are still discovering more of them. To put that number in perspective, red wine has around 600 observed compounds that contribute to flavor. Therefore there is a lot of variety when it comes to coffee, especially when one considers all of the steps it goes through to make it into your coffee mug. From planting to harvesting, processing to shipping, roasting to brewing, there are a host of variables that can affect the finished product. So, being able to try different high quality expressions of this complex culinary item, enhances the enjoyment of the beverage and expands my palate in exciting ways. I have also been consistently impressed at how good of a job the guys at My Coffee Pub curate great selections of coffees from talented roasters across the U.S.
So in the spirit of experimentation I wanted to share some of the fun things I have been able to do with the coffees from My Coffee Pub. When I first get a coffee I want to “dial it in” to my preferences. Dialing it in involves discovering the optimal brew method, water-to-coffee ratio, grind setting, temperature and dwell time that suits the particular coffee at hand. My two favorite ways to brew coffee at the moment are via a Chemex and an Aeropress. It is the Chemex, however, that is my daily brew method and probably a more common brew methodology amongst those who manually brew at home.
At the beginning of March I bought a Pal Coffee digital refractometer. A refractometer measures the refractive index of light through a solution and tells you the total dissolved solid contents of the extract. You can take that data point and derive the extraction percentage yield for your particular coffee brew. Basically this just means how much of the finished product coffee were you able to pull out of the grounds. The optimal range for drip and pourover coffee is between 18%-22% extraction. So with my new coffee toy in hand, it was time to get down to business using my Chemex. While seeking to dial in the Papua New Guinea from Argo Sons last month, and the Ethiopian Yirgacheffe from Tinker this month, I decided to see the effect of temperature on my cupping scores for each coffee. The challenge with coffee is that there are so many variables. I had to make sure that as many of them as possible were controlled. I controlled for grind size (same setting on Baratza Vario), water-to-coffee ratio (30 grams of coffee to 450 grams water), pre-infusion time (45 seconds), total pour time (2 min and 30 seconds, also each brew finished up at around 4 minutes) and final extraction percentage (all 12 brews were kept within a parameter band of 2.49% (18.9%-21.39%)). The cupping scores were derived from a proprietary cupping form that I designed for personal use, so the numbers do not indicate quality compared to other cupping score ranges, just my in-house numbers. In other words, a score of 50 is not out of 100 or based on traditional cupping score convention, but a higher score is better. Below is a plot of the results.
The results were very interesting (note: The Ethiopian Yirgacheffe is the blue line and the Papua New Guinea is the orange line). The first thing I noticed was that there was a clear general trend for both coffees. There was a low end peak and a high end peak for each coffee, resembling two humps. I was also struck by the fact that at 198 degrees both coffees got very high marks but then dipped low on the 200 degree brew. From 200 degrees they got better at 202/204 and the Ethiopian coffee scored it highest mark at 206 degrees. The Ethiopian coffee had a lot of symmetry on each side of the 200 degree mark whereas the PNG increased in cupping score after 200 degrees but never quite got the results that it did at the cooler end of the temperature spectrum.
Clearly, the Ethiopian took the higher brew temperatures much better than the PNG. The PNG preferred the lower temperature with 198 degree water resulting in an optimal brew. This preserved all of the great sweetness in the coffee without bringing in a lot of negative bitter compounds. For the Ethiopian I found that the 206 degree water brought out excellent sweetness and acidity but did not bring out negative bitters. The results also point to a “safe zone” of around 198 degree water where both coffees performed very well. This may be a good place to begin when brewing coffees for the first time. I look forward to continuing to find the optimal brew parameters for the coffees I get from My Coffee Pub and will keep an eye out to see if these trends persist. If so, I may be writing about the “200 degree slump” on my blog sometime soon.