Roast Approach: Rwanda Nyamasheke Muhororo Natural

Today's coffee that we are going to approach is the Rwanda Muhororo Natural.  The coffee comes from the Nyamasheke region of Rwanda, on south western edge of Lake Kivu.  The coffee is 100% Red Bourbon, characteristic of Rwandan production.  The coffee is natural processed.  

Arrival QC:

The coffee arrived in February, 2026 to the United States, at which point part of the lot was taken up to the Swiss Water decaffeination plant in Vancouver, British Colombia.  When the coffee arrived to the United States, it had a humidity level of 11.8% and density of 1.15 g/ml. 

The sample roast was preformed on an Ikawa with the roast profile that can be found on our website.

The Roaster:

For these roasts, I'll be using a Proaster 1.5 kilo drum roaster hooked up to natural gas.  Batch size is 400g, approximately 35% of roaster capacity.  I've used a small batch size on this roaster to get closer to mimicking the gas power that you might find on a larger production roaster.  It must always be mentioned that each roaster is different.  The type of probe, placement of probe, and batch size will all influence the way in which bean probe temperatures are registered in a roaster.  With that said, don't read too much into the exact temperatures, but look more closely at the theory behind the approach, time spent in different development periods, and rate of rise to get a better idea of how to translate this profile over to your own machine. 

The Goal:

When I started roasting this coffee, I began with roasting 4 different roast profiles.  I played around with heat application during various phases of the coffee roast.  I also roasted one of the profiles with 3 different charge temperatures to see how the coffee reacted to initial heat application and momentum.  On the cupping table, all of the coffees were tasting "green", underdeveloped and lacking in sweetness.  I had cupping notes of "lemongrass", "lemon balm", and sharp tart acidity on all of them.  Even when I was trying to give more development, I ended up jumping right to bitterness and totally seemed to bypass caramelization.

I also noticed something very odd in my roasts of this coffee.  Typically, when I roast a coffee that has approximately this density and humidity level, I experience a roast loss that is between 12-13%.  However, I was getting over 15% roast loss on these roasts, even with minimal post crack development.  In any other coffee, I would say that a 15% roast loss is a medium-dark roast.  Yet, these coffees were exceeding 15% roast loss and still tasting underdeveloped.  What in the world is happening here?

In a 2017 article by Chris Kornman in Daily Coffee News,Kornman details experiments with roasting high water activity vs. low water activity coffee.  From these experiments, we know that a low water activity can interfere with the Maillard reaction, which can result in a lack of sweetness.  We also know that most of the roast loss that occurs in a coffee comes from evaporation.  Water molecules are necessary to the Maillard reaction occurring.  The chemical reactions of Maillard (first early Maillard reactions, the followed by the reactions of caramelization and the eventual development of mellanoidins) are a cascade of reaction, with early Maillard creating the precursors necessary for the later reactions.  At the foundation of this house of cards is the proper amount of water molecules.  

In these roasts, I had a high roast loss (more of something than normal is missing in this bean by the end of the roast), and it tasted like I had rushed through the roast with minimal time spent in the Maillard phases.  My working theory became that the coffee lost more than a normal amount of water during drying, leaving it with less water molecules than it needed for Maillard.  The result, not enough Maillard reaction, not enough precursors for caramelization.  Sour coffee, high roast loss.

Hopefully this will provide you with the background you need to confidently approach this coffee in your own roasting adventures.

If you would like to learn more about my four phase approach to roast profiling, check out my “Roast Approach: Roast Strategy” blog.

The Approach: 

To address the issues I was experiencing with development, I wanted to try and keep as much moisture as possible in the drum of the roaster through the roast.  My theory was that if there was more moisture in the drum, the coffee would experience less evaporation and, in turn, would have the precursors necessary for proper Maillard development.

My strategy was to use a very restricted air flow schedule.  I roasted with as little airflow as I could, being mindful to not create a high fire risk and to try and give enough airflow at the end that I didn't end up with "muddy flavors" in my coffee. 

I still ended this roast with a roast loss of 14.5%, which most roasters would equate with a darker roast (although it clearly did not taste like a dark roast).  My first round of roasts had roast loss of 15.25%, with a similar end temperature and development time.  My strategy kept an extra 0.75% of the coffee weight, which I assume is likely attributed to internal moisture.

In the cup, the coffee had more of the fruit forward characteristics that I would look for in a natural.  The fragrance was of fresh strawberry, peach, white chocolate and cream.  Peach, white grape, Fuji apple were predominate tasting notes for the cup.  The acidity was finally balanced and reflected the malic acidity of white grape and apple.  I also experienced more developed body and a coating mouthfeel. 

The Takeaway:

This is definitely a coffee that I think requires more experimentation with.  It's curious to me that in the sample roast, which was done on a fluid bed Ikawa with convective heat transfer, the coffee did not have the flavor deficits that I found on the traditional drum roaster.  I am curious if the Ikawa was better at maintaining a more moisture rich environment through the drying phase.  Hopefully one day I will have a lab full of extravagant tools and unlimited time to test these theories.   

This is yet another instance where my knowledge of roasting chemistry came in clutch for problem solving and troubleshooting this coffee.  I'm really excited to hear how everyone's coffee turned out.  If you experienced any of these challenges in roasting this coffee, be sure to leave a comment and let me know how you approached it!

Happy roasting and best of skill to all of our competitors!