There are four types of coffee beans: Arabica, Robusta, Liberica, and Excelsa. Among the four varieties, arabica and robusta are the most well-known.
Coffee characteristics are measured by the quality of the bean and the intensity of flavor, aroma, acidity, and taste (body) mild or bold.
Arabica
Arabica coffee beans have a smoother, sweeter, and more nuanced flavor than other coffee types, with notes of fruit, chocolate, nuts, and caramel. They are also lower in caffeine and more acidic, making them less bitter and easier to drink.
Arabica beans are the most widely consumed coffee beans worldwide, making up approximately 60% of the globally produced coffee. It is believed to be among the very first coffee beans ever consumed. That was first cultivated in the highlands of Ethiopia centuries ago.
However, they are more challenging to cultivate compared to other coffee beans. Arabica beans need extra shade, water, and a high altitude of at least 2,000 feet to grow properly. This makes them more expensive.
Robusta
Robusta coffee beans are the second most common type of coffee, accounting for around 40% of coffee production. The plants earn their name due to being hardier than Arabica plants, having reduced susceptibility to disease, and thriving in diverse environments, including low altitudes.
Robusta beans are smaller, and rounder and have a higher concentration of caffeine than Arabica beans. Robusta coffee has many unidentified heirloom varieties, but you can categorize them into Erecta (upright varieties) or Nganda (spreading varieties). The flavor profile is dark and earthy and can have bitter or burnt flavors. Although it is considered inferior to Arabica, it can add complexity when used as an Arabica-Robusta blend.
Liberica
Liberica coffee beans are a distinct and less common species of coffee beans. It originated in Liberia and is primarily cultivated in Southeast Asian countries like the Philippines, Malaysia, and Indonesia. Liberica beans are known for their bold, full-bodied flavor with woody and smoky undertones, accompanied by a unique aroma that can be described as floral or fruity. The beans are large and irregularly shaped, often exhibiting a “peaberry” appearance. Liberica coffee faces cultivation challenges due to its susceptibility to diseases and pests, requiring specific climatic conditions for successful growth. Although less prevalent in the global coffee market compared to Arabica and Robusta, Liberica beans are sought after by those seeking a distinct and uncommon coffee experience.
Excelsa
Excelsa coffee beans were once considered a different type of coffee but have now been reclassified as a subtype of Liberia. Like other Liberica coffees, it grows on tall trees rather than shrubs.
Excelsa coffee offers coffee enthusiasts an intriguing taste experience with its distinctive flavor profile. While not as widely known or cultivated as Arabica and Robusta, Excelsa beans provide an opportunity for coffee lovers to explore different flavors and expand their coffee palate.
THE ORIGINS OF EXCELSA as a must read…
While today, excelsa is cultivated in southeast Asia (including Vietnam and the Philippines) and India, it was actually first discovered in 1903 in Central Africa, where it was also known as Coffea dewevrei or dewevreié.
Until around 15 years ago, excelsa was believed to be a species of the Coffea genus in its own right. It was only in 2006 that it was officially reclassified as the dewevrei variety of the liberica species.
The resulting confusion has underpinned most of excelsa’s recent journey in the modern coffee market. This has also been driven by the fact that the “excelsa coffee” label is often used when selling liberica varieties (much like how the words “robusta coffee” are broadly used to describe all C. canephora varieties).
The confusion in turn leads to more generalisation and synonymous use of these terms, which consequently means less reliable data on accurate production levels. It may also be responsible for decreases in the quality of excelsa coffee. Altogether, this gives farmers little incentive to implement quality control measures.
Ultimately, the International Coffee Organization (ICO) offers no official statistics on the production or trade of excelsa coffee. When we reached out to the ICO to ask why, secretariat and communications officer Rena Gashumba said that “the demand for excelsa and liberica coffee is not considered commercially significant”.
EXCELSA PLANT PROFILE
Despite the 2006 reclassification of excelsa as the dewevrei variety of the liberica species, researchers continue to debate whether or not it should be recognised as a species in its own right.
Excelsa coffee grows best at altitudes of between 1,000 and 1,300 m.a.s.l., and unlike arabica and robusta, it is an arboreal (tree-like) plant, rather than a shrub. This means it requires vertical space to grow, rather than growing into the area around it on the ground. And while it is productive and resilient, excelsa is difficult to manage and requires extensive care.
The leaves of the excelsa plant are large (on average, 26cm long by 13cm wide) and leathery. Its flowers bloom multiple times throughout the harvest season, despite the fact that fruit maturation takes around a full year. These flowers are bigger than those on arabica and canephora plants. Excelsa also produces asymmetrical beans that are, on average, around 9mm long and 6mm wide.
Excelsa beans are also lower in caffeine than both canephora and arabica. Dr. Oliveiro Guerreiro Filho is a senior researcher at the IAC in Brazil. He tells me that the organisation’s germplasm bank shows that the caffeine levels in excelsa beans range from 0.86 to 1.13g per 100g, compared to 1.2 to 1.5g for arabica and 2.2 to 2.7g for canephora.
However, despite this, excelsa trees are resistant to many of the common diseases and pests that other plants are not. These include coffee leaf rust, nematodes, and the coffee leaf miner moth. Excelsa is, however, susceptible to trichomycosis, a fungal disease.
Variety or species?
Komal Sable is a fifth generation coffee farmer working at South India Coffee Co., a producer and exporter that works with specialty Indian arabica, robusta, and excelsa beans from farms in the Western Ghats.
She notes that despite excelsa’s classification as a variety of liberica, there are key differences in even the shape of the beans between the two. The liberica bean, she tells me, is shaped like an almond, whereas excelsa beans are smaller and rounder.
Komal goes on to tell me that any differences between the two beans are typically overlooked. As a result, in India, she says the tendency is for producers to group them together. Both trees are often referred to as “mara kaapi” in the local language, which directly translates to “tree coffee” – leading to further confusion.
Oliveiro says that the species vs. variety debate has continued despite the reclassification in 2006. This, he says, is largely down to conflicting results between the genetic studies of the liberica and excelsa species.
According to Oliveiro, there are findings that indicate high levels of genetic differentiation between excelsa dewevrei and other cross-pollinating liberica varieties. Further studies comparing the structure of chromosomes in both species also suggest that despite their similarities, excelsa and liberica should be considered separate species.
GROWING EXCELSA: THE CHALLENGES
As well as having larger leaves, excelsa trees can grow to be more than 15m tall, with a treetop diameter of 6m to 7m. Thanks to the plant’s high productivity levels, farmers need to frequently prune the trees, which can be difficult to manage at these heights. This means more labour is required, further increasing the cost of production. This is just one of many reasons that excelsa hasn’t spread further afield among coffee producers.
Oliveiro also points out that the species’ prolonged ripening period contributes further to a higher production cost, and also makes it difficult for farmers to implement any kind of plan for cultivation.
However, he says the lack of awareness is arguably the most significant barrier. “Contrary to what happens with the other marketed species, there are no improved cultivars or technological packages based on solid and well-established research for the cultivation of both excelsa and liberica coffee varieties,” he notes.
Ultimately, the market for this species is minuscule. Even in the communities where excelsa is grown, knowledge is usually shared from generation to generation. Furthermore, farmers often keep the beans for their own consumption, as there’s no real demand.
Finally, even if there was interest in producing excelsa at a larger scale, there’s no established commodity market or standardised price, making regular trading at any kind of major volume practically impossible.
ROASTING AND CUPPING
Despite the issues with its production, when excelsa is farmed and processed with care, it can yield a complex and interesting cup profile.
Komal says: “In 2020, we processed 200kg of excelsa [coffee] for specialty consumption. We started 2021 with orders that would require us to process at least 5 tonnes of [coffee] to fulfil them.”
She says that the excelsa bean has a denser mucilage than arabica, and has far fewer soluble solids. This means that existing roast profiles for excelsa shouldn’t be derived from any other bean, and that new curves and best practices must be used.
In addition, its lower solubility means that excelsa beans may need to be roasted at higher temperatures or for longer periods to reach optimum flavour profiles.
Roasters who work with excelsa state that medium-light roasts can produce berry-like and fruity notes, as well as woody and popcorn-like flavours. As the roast gets darker, the bean yields a fuller body with notes of chocolate and cream.
Finally, while natural processing is by far the most common, Komal notes that South India Coffee Co. currently offers double fermented black honey excelsa, with “complex, very berry-like” notes.
DOES IT HAVE POTENTIAL?
Despite its insignificant presence across the global coffee market, excelsa’s lower optimum altitude may be an indirect solution for farmers who are affected by climate change.
In theory, cultivating excelsa could prevent them from continually moving to higher altitudes to achieve target growing temperatures. However, without any kind of commodity market and the current, minuscule levels of demand, a full switch is highly unlikely and an unrealistic proposition.
More realistic, perhaps, is the possibility of excelsa trees being used as grafting rootstock for arabica and robusta plants. This is because its roots grow faster and are more resistant to certain diseases and pests in some coffee producing countries.
For the specialty coffee sector, which places high value on rarer and more exclusive beans, Komal says that “there is a market”.
However, she adds: “Due to the challenges in harvesting, I think growing it at scale may be a problem. The lack of a C price for this [type] of coffee is a challenge too.
“The art and science behind the farming of excelsa is still very much in its nascent stages. However, we hope that with continued experimentation and buyer feedback, we can help establish it as another specialty option for the consumer.”
It’s clear that the biggest barrier for excelsa coffee is its lack of awareness. This has in part been driven by confusion regarding the debate on whether or not it is a species, which has likely led to inaccurate reporting.
In time, with more research, more data, and more production, there could be more of a market for this unusual bean, but as it stands this does not seem likely. That said, with climate change already affecting the area suitable for coffee cultivation, it seems more important than ever to investigate more resilient and robust varieties. Even if excelsa isn’t suitable for widespread cultivation, its genetic makeup may offer a “hidden” solution.
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