Hambela is the new Yirgacheffe! So says Satta in part 1 of this blog series, about how Ethiopian coffee profiles are changing. Read it here.
In this post we look at what actually impacts the flavour profile of the cup. In the case of most Ethiopian coffees, it comes down to nature’s circumstances and phenomena, including the micro-climate, altitude, surrounding vegetation, and the soil composition. Of course, human intervention is a big part of the cup too. Read on to discover more.
The richer the soil, the more nutrients will be made available to the coffee tree, the better the cherries will mature and generally that will result in a more complex cup. Hambela coffees are a good example of such a profile, as it is a relatively new coffee growing region so soils are virgin. Healthy, uncultivated soils are usually porous and “lively”, meaning full of movement from worms and other mico-organisms. The more commercially cultivated the soil, the less porous, nutrient rich and structured it will be, and the harder it is to cultivate higher yielding trees that bear complex cherries. Keeping a soil healthy requires planting leguminous herbs and nitrogen emitting trees to create an environment where micro organisms survive. It is possible to revive commercial soil using these practices, but it takes many years before it returns to its original state.
Altitude and temperatures
Altitude is usually correlated to cooler temperatures. The colder the temperature, the slower the maturation of cherry and the drying of harvested coffee, which equals more acidity and complexity in the cup. Chelbesa coffees are a great example of this. Chelbesa is located in a valley close to Worka town at 2300 masl. During the day the temperature rises to 30 degrees and decreases to as low as 8 degrees some nights. We believe that these temperature fluctuations affect drying in a positive way which increases acidity and lifespan of the greens. The downside for areas at these altitudes is that they are generally more likely to be cloudy and rainy, especially with recent climate changes, which can negatively affect quality. Chelbesa has so far been spared these issues.
Shade and leguminous vegetation is another way to cool a farm. Not only are they important for soil health, they also protect the cherries from heat and sun. Indigenous trees such as Wanta, Corch, Birbira and Shola are common on coffee farms, and crucial for maintaining a farm’s biodiversity.
Many human interventions can impact the cup profile, including methods of processing coffee from pre-harvest to dry milling such as:
- Pre harvest practices
- Harvesting; ripeness of cherries
- Fermentation; anaerobic, dry
- Drying; thickness of layer on drying beds
Pre harvest usually includes pruning the trees to increase yields and quality of cherry. The fewer branches the tree has to send nutrients to, the more it will focus on developing cherries, enabling them to fully ripen. Pruning is usually practiced where agronomists actively educate farmers.
Harvesting practices are different in all the micro regions. Some farmers are used to washing stations buying any quality available from the farmers. Others, like in Worka Chelbesa area, the farmers wait until their whole tree is full of ripe cherries and then harvest. This last practice is great for consistency and quality.
Fermentation is said to be the creator of flavour in coffee. It depends on a lot of factors. Water quality can accelerate the development of specific bacterias that might be positive or negative. The cement in the fermentation tanks holds bacteria and can affect the fermentation volatility. Outside temperature can affect the rate of fermentation and prolong or shorten the time. Generally, cold weather and longer fermentations of 48-72 hours create more complexity in the cup. Finally BRIX (sugar level) and pH (4.0) can be monitored to find the optimal fermentation time, though this is not normally practiced in Ethiopia.
Drying might be the most crucial part of processing coffee. Too fast and the coffee could age quickly. Too slow and the coffee might develop moldy or phenolic defects. Not enough and the coffee might never show it’s true flavors. Optimal drying for washed coffees is 12-15 days and for naturals 15-20 days. We look for moisture content of 10.5% and a water activity of 0.55.