FERMENTATION PROJECT: James Hoffmann x Lucia Solis

Lucia studied Viticulture and Enology at the University of California, Davis, specialising in microbiology and fermentation science. She spent nine years working in wine production in Napa Valley before transitioning her focus to coffee in 2014.

Today, she is a coffee fermentation and processing specialist with over 12 years of international experience, having worked alongside producers in more than 15 countries.

Lucia supports coffee producers in rethinking processing as a strategic opportunity to add value and reduce risk at the wet mill. Her work centres on simplifying and streamlining protocols from fermentation through drying, creating greater clarity and operational control.

By applying microbiological principles, she helps producers develop reproducible cup profiles while bringing stability to one of the most variable stages of coffee production. Her approach emphasises scientific rigour combined with practical simplicity — ensuring that innovation remains accessible and scalable.

The coffee was harvested at Finca San Miguel Urias, a farm owned by Hector and Lilian Leal and operated under Rueda Farms. The farm is located in Guatemala's Antigua Valley, between Ciudad Vieja and San Miguel Dueñas, at 1,460 - 1,540 masl.

The coffee is predominantly Caturra, making up approximately 85% of the lot, alongside around 15% H1 and a small amount of Bourbon. Harvest began on 10 December 2025, with the final coffee used for this project coming off the drying patios on 23 February 2026.

Each of the four coffees began with the same starting material, allowing us to look more closely at how different approaches to fermentation can influence the final cup.

Mechanically Demucilaged:

The first coffee acts as the control for the project. After pulping, the mucilage is mechanically removed rather than broken down through fermentation, significantly limiting microbial activity during processing. As a result, the cup offers a clearer look at the characteristics coming from the variety, growing conditions and agricultural practices at Finca San Miguel Urias.

Wild Fermentation:

For the second lot, the coffee undergoes a 48 hour submerged fermentation using the naturally occurring microorganisms present on the coffee and in its environment. These local populations of yeasts and bacteria break down the mucilage surrounding the seed, making this closest to a more traditional washed fermentation. Because the microbial population isn't controlled through inoculation, this is also the least predictable of the four processes.

Lactobacillus Fermentation:

The third coffee is also submerged for 48 hours, but this time the fermentation is inoculated with Lactobacillus bacteria. Introducing a selected microorganism gives greater control over which microbes dominate the fermentation and the metabolic activity taking place. Lactic acid bacteria can contribute to the production of organic acids during fermentation, influencing the coffee's perceived acidity and complexity.

Saccharomyces Yeast Fermentation:

For the final lot, the 48 hour submerged fermentation is inoculated with Saccharomyces yeast. Yeasts metabolise sugars within the coffee's mucilage and produce a range of metabolites during fermentation, some of which can contribute directly or indirectly to aroma and flavour development.

Together, the four coffees aren't intended to demonstrate that one fermentation method is inherently better than another. Instead, they give us a controlled way of tasting how microbial activity and fermentation can influence a coffee while the variety, farm and starting material remain the same.

Caturra is a pure-line dwarf mutant of red Bourbon, discovered in Minas Gerais, Brazil in 1937. Its leaf and fruit characteristics resemble Bourbon, with cherries that can be either red or yellow, known as Caturra Vermelho and Caturra Amarelo, respectively. The plant is short with abundant lateral and secondary branches, giving it a vigorous and compact appearance. Due to its susceptibility to coffee diseases and lack of hardiness in frost-risk areas, Caturra was never cultivated in Brazilian lowland plantations. However, its broad adaptability has led to its widespread cultivation across Colombia and Central America, where it thrives at higher altitudes.

The variety H1, or Centroamericano, is a first-generation (F1) hybrid. It originates from a cross between the rust-resistant variety Timor 5296 and the Ethiopian landrace variety Rume Sudan. Timor 5296 itself is the progeny of a spontaneous interspecies cross between Robusta and Arabica, discovered on the island of Timor in the 1920s. As a first-generation hybrid, Centroamericano isn't considered stable, seeds from these plants won't necessarily produce offspring with the same qualities. However, Centroamericano boasts impressive traits: it's resistant to coffee leaf rust, extremely high-yielding, and has proven to have exceptional cup quality potential when well-managed at high altitudes.

Bourbon is one of the most culturally and genetically significant varieties of Arabica coffee in the world. This tall variety is characterised by relatively low production and susceptibility to major diseases. However, it produces excellent cup quality when grown at high altitudes.

The first Bourbon plantation dates back to 1715 when the variety was introduced from Yemen to Bourbon Island, now known as La Réunion. Bourbon traces its origins to a broad group of C. arabica specimens that developed naturally and is still cultivated in Central America today.

Depending on the sub-group, Bourbon coffee can produce red, yellow, or orange-coloured cherries. The plant's shoots initially grow upwards at a 45° angle to the stem, and the stems are sturdy. Young leaves are green, and the plants generally have broader leaves and rounder fruit and seeds than Typica and its descendants.

The 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.