June 24, 2020

How to Roast Kenyan Coffee


Kenya is Africa’s fifth-largest coffee producer, and its six producing regions are known for growing many varietals of high-quality coffee – thanks to the country’s high altitudes, moderate temperatures, even rainfall patterns and volcanic soil. 

While Kenyan coffees are known for being complex, fruity, full-bodied, and acidic, developing this flavour profile to its full potential will depend just as much on how the coffee is roasted as it does on the coffee’s origin and inherent qualities.

Here’s what makes Kenyan coffee unique, and what to consider when roasting it. 

Lee este artículo en español Consejos Para Tostar Café de Kenia

Coffee pickers sorting Kenyan beans

What Makes Kenya’s Coffee Unique For Roasters?

For roasters looking to make the most of their green beans, care needs to be taken during selection, as the type of beans used will impact the roast outcome. Here are a few factors that uniquely impact Kenyan coffee beans.

Bean Size Matters

Kenyan coffee is sorted and graded by size, with common categories including E (Elephant, which is the largest found in Kenya), PB (Peaberry), AA (the largest specialty bean), and AB (a mixture of large A and slightly smaller Bs). After being sorted by size, beans are graded by quality using a scale of one to ten and then separated into different lots. 

The type of beans you buy with will impact how you roast it. Mikkel Selmer is Head of Coffee at La Cabra Coffee Roasters in Denmark. He says that if roasting AA beans, their higher density should be taken into account and your batch size lowered. Eros Ceresa is Green Bean Buyer for Falcon Specialty Coffee, and also has insight into the size differences between different grades of Kenyan coffee beans. He says that while there isn’t a significant difference between AA and AB, PB will require a different approach to charging temperature, and how heat is applied and then reduced during ROR descent. Here, he keeps temperatures lower to avoid these smaller beans tipping or scorching. 

You may also like What’s an AA SL-28? Get to Know Your Kenyan Coffees

Kenyan coffee beans being processed

How Processing Impacts Your Roast

The processing that many Kenyan coffees undergo should be taken into account, as while many still favour the traditional double processing methods, others use natural and honey processing. Casper Rasmussen, Co-founder of the Coffee Collective in Denmark, has some insight into this. He says, “So far, we have only had experience with pulped naturals from Kenya in our production. They acted surprisingly like a normal washed Kenyan in the roaster. Normally you have to roast a natural quite different to a washed”.

Eros has found that natural and honey processed coffees can be roasted slightly lighter than washed coffees. He explains, “If I’m trying to stay as light as I do for a natural, my washed coffee will have the herbal, creamy, grassy flavour, which personally I deem bad.”

Knowing the characteristics of your beans and how they’ve been developed will keep you from making unnecessary mistakes and ensure the beans you select will release the flavours you’re looking to showcase with roasting.

Kenyan coffee beans being graded

Managing The Roasting Process

Having a predetermined flavour profile in mind and understanding what you want to stand out in a cup will help you guide your roast to where you want it to be. Using your experience with roasting other beans and having a general idea of how to get there is a great start – as is understanding that tweaks will always need to be made throughout the process. It’s also worth note that most roasters have their own ideas and thoughts when it comes to roasting this bean.

Mikkel says that when he roasts Kenyan coffee, he usually has an idea of the general notes he wants to highlight with roasting, which he describes as “undiluted Ribena juice.” However, he adds that “it’s easier to distinguish that fresh blackcurrant note that we want in a light roast… so that’s what we aim for… we look for cleanliness and importantly, that sweet and sour balance.” He adds that while he usually focuses on density over origin when roasting, that “ [Kenya is one] of the countries we buy coffee from where we have the clearest idea of what we’re looking for in terms of cup profile.”

On the other hand, Casper has found that as we generally know what flavours we expect from a Kenyan bean, we can look more closely at their individual characteristics. He says, “As with all coffees we source first and foremost we look for sweetness. For us, this is the best indication if the coffee is well produced.”

Keep your customer’s tastes in mind, as many potential customers can be put off by coffees with too much of a “sour” flavour, while coffee connoisseurs with more experience tasting specialty might expect its bright fruity punch. 

Finding a profile pleases everyone is the challenge. However, there are few general guidelines worth observing, no matter who you’re roasting for. 

  • Drop Temperature – as Kenya’s AA beans grow at exceptionally high altitudes, it produces a very dense bean. This means you’ll need a drop temperature high enough to create enough energy to see the roast through to the end. 
  • The drying phase – if you want to preserve the fruity acidity of your coffee without giving it a heavy body, shorten your drying phase by applying extra heat shortly after the turning point on the roast.
  • The Maillard phase – to prevent the acidity present from overwhelming the coffee, its tartness must be countered with some sweetness. Stretching out the Maillard phase will help find that balance.
  • Roast Duration – The longer the roast, the more body is created. Here, finding the right length of roast is something that may need to be tuned in over time, and will also depend on whether you’re roasting for espresso, filter, or omni. 
  • Development time – Depending on your roast duration and chosen extraction method, development time can differ. To retain as much acidity as possible, shorten the development time, but ensure the bean fully develops – as a failure to reach this can leave too much fruity acidity. Eros says, “Don’t be afraid of building up heat approaching the first crack… If you don’t have enough heat to sustain in the second part of the development… you’re going to end up baking the coffee and that will really cancel everything”.

Finishing Off

Once your Kenya coffee has been roasted, it should have enough time to degas. Their high density and lighter roast can slow the degassing process, which can take up to a month of resting for full flavour development to occur.

If you’re planning on using it in a blend to balance or complement another coffee, remember that Kenyan coffees can easily hold too much acidity for the day to day espresso drinker, and in some cases curdle or sour a milk-based beverage. This will allow you to adapt your roast for sweetness and dial down its natural acidity. A high altitude Colombian coffee’s complex, delicate acidity would balance a Kenyan coffee.

Casper has worked with a Kenyan blend for quite some time now, “As for any coffee for brewing as espresso we tend to have a longer profile to ensure that the brew does not become too acidic. Sometimes a Kenyan coffee can be too overpowering and just take all the attention from the other coffees.”

While Mikkel and Casper might take different approaches to roasting, they both agree that it starts with sourcing quality coffee. Mikkel recommends looking for high-quality beans and to ensure you follow your roastery’s existing quality control procedures, and Casper adds that with a quality green coffee, the roasting process is much easier. 

Ultimately, roasting Kenyan coffee requires fully understanding it and treating it with care, in order to uncover its full potential and create a clean profile free of roast defects. While following the steps above can help finetune your roasting efforts each batch needs to be treated individually, and just because you have roasted a Kenyan coffee previously doesn’t mean that you will get perfect results straight away with a similar profile. 

Enjoyed this? Then Read Kenya AA, Colombia Supremo: Understanding Coffee Grading

Photo credits: Coffee Collective

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