THIRIKU, AA Washed

Showcasing the finest qualities of Nyeri County, Kenya, the Thiriku Farmers Cooperative Society produces an exceptional single-factory coffee with distinctive characteristics in every cup. Guided by the core principles of transparency and trust, this award-winning cooperative consistently delivers accountability, consistency, and excellence for all stakeholders.

Thiriku is located along the Nyeri–Giakanja–Ihithe road, in a lush region with rich volcanic soils from the Aberdares, ideal conditions for cultivating coffee. The county itself is centred around a hill historically known to the indigenous Kikuyu as “Kia-Nyiri,” a name dating back to 1902, when local warriors fiercely defended their homeland, giving the renowned Nyeri region its modern name.

Operating independently as a single-factory cooperative, Thiriku is a dedicated community of 2,000 active members. By sourcing farm inputs for farmers and maintaining a dedicated demo farm, the society supports remarkable consistency, recently achieving a harvest in which an impressive 89 percent of the yield was classified as premium grade. With multiple trophies for being the highest payer and for winning the EAFCA Cup, the wet mill remains highly active, gathering a small early crop between April and July, followed by a substantial main harvest from October to December.

To ensure the highest quality, Thiriku uses a meticulous, tightly controlled wet-processing method. Ripe red cherries are selectively handpicked and carefully sorted, then pulped and fermented for 12–24 hours. The sticky mucilage is then washed away in clean water channels and soaked in fresh water for a further 12–24 hours, a crucial step that enhances clarity and acidity, before being slowly sun-dried on raised beds to the ideal moisture content.

This post-wash soak was originally employed to ease peak-season bottlenecks, when drying beds were full. By soaking, producers could buy time for coffees to finish drying and for fresh beds to be cleared. It’s widely speculated that this practice contributes to the classic Kenyan profile of sparkling acidity and deep purple-fruit flavours. In recent years, volumes in Kenya have declined in part due to rising real estate prices and reduced interest in coffee farming among younger generations. As a result, these soaked coffees are becoming less common, and some attribute the changing flavour profiles of this origin to this shift. Whatever your take, Kenyan coffees continue to deliver on quality expectations despite the many challenges facing the industry there, and have always held a special place in our heart.

SL28 is one of Africa's most renowned and esteemed coffee varieties. Scott Laboratories originally selected it in the 1930s from a drought-resistant population in Tanganyika (now Tanzania). The initial tree caught attention due to its resistance to both drought and disease. SL28 was then developed through pedigree selection, a breeding method where ancestry records are meticulously maintained. In this process, selected parent plants are crossed, and their offspring are carefully segregated. Seeds from plants displaying desired traits are chosen and grown over several generations until the characteristics stabilize.

Initially widespread in Kenya, SL28 has since expanded to other African regions and even Latin America. Recent genetic studies have linked SL28 to the Bourbon genetic group. It's highly valued for its superb cup quality, especially when grown at high altitudes. While SL28 is drought-tolerant, it remains susceptible to major diseases. Remarkably, it's known for its resilience to minimal plantation management, even 60-year-old, neglected trees can remain highly productive.

SL34 was originally selected in Kenya in the late 1930s at the Scott Agricultural Laboratories. The variety was selected from a single tree on the Loresho Estate in Kabete, Kenya, as research at Scott Laboratories was often conducted in cooperation with local, private estate owners. The tree was labelled "French Mission."

French missionaries known as Spiritans established a mission in 1893 at Bura (Taita Hills, Kenya), where they planted Bourbon coffee seeds from La Réunion island. Seedlings from Bura were brought to another French Mission in Saint Austin (near Nairobi) in 1899, and from there seeds were distributed to settlers willing to grow coffee. This is the origin of "French Mission" coffee.

Because coffee seeds came directly from La Réunion via French missionaries, French Mission is widely understood to be another name for Bourbon. However, recent genetic tests have indicated that SL34 is related to the Typica genetic group, suggesting the original story about SL34 being selected from a French Mission population might be incorrect.

SL34 is adapted to high-altitude areas with good rainfall. It is characterized by dark bronze-tipped plants with some green-tipped strains. It's well-known for its exceptional cup quality but is highly susceptible to coffee berry disease.

Ruiru 11 was developed following a coffee berry disease (CBD) epidemic in 1968 that decimated 50% of Kenya's coffee production. In response, an intensive breeding program was established in the 1970s at the Coffee Research Station in Riuru. The program focused on creating a compact variety suitable for intensive planting, with high yields and excellent cup quality.

In 1985, Ruiru 11 was released. This variety is a complex hybrid created through a two-step process. First, varieties chosen for CBD resistance (Rume Sudan, Timor Hybrid, K7) were crossed with others selected for good cup quality (N39, SL28, SL34, Bourbon). The resulting progeny was then crossed with various Catimor lines, chosen for their compact size and resistance to both CBD and leaf rust.

Batian was developed through a breeding program at the Coffee Research Station in Ruiru, Kenya. Released in 2010, Batian is a tall, high-yielding variety with good cup quality, tolerance to leaf rust, and resistance to coffee berry disease. This hybrid was created over several generations by crossing SL28, SL34, Rume Sudan, N39, K7, SL4, and the Timor Hybrid.

he washed process was designed to minimise the risk of off-flavours caused by uncontrolled fermentation during the natural process. Cherries are typically sorted using a flotation tank, where under-ripe or defective fruits float to the top and can be removed. The remaining cherries are then pulped and left in a tank to ferment until the sticky fruit mucilage is soft enough to be washed off the parchment, a paper-like layer surrounding the seed.

The design and cleanliness of the tanks used for fermentation are crucial, and the type, degree and speed of microbial activity depends on various factors. These include the amount of fruit remaining, the presence of bacteria and yeasts, whether the tank is filled with water, and the environmental conditions.

Once the mucilage has sufficiently degraded, it's washed away with water. The remaining parchment coffee, as it's commonly called, is then dried until it reaches a safe moisture content. The bacteria rich and sugary water used in the process must be treated carefully, as it can cause algae blooms if it enters streams and rivers.

In situations where large amounts of coffee are processed in bulk, such as in Ethiopia, some operations have found it economical to use a mechanical de-mucilager. This device removes all the fruit from the parchment with minimal water, bypassing the fermentation stage entirely. However, some believe this leads to a reduction in cup quality, as many flavour precursors are created through fermentation.