Sironko Station Natural Anaerobic Fermentation with PK-1 Yeast

About
Processed at Mountain Harvest’s central hub of innovation and research—Sironko Station, this lot is carefully overseen by Ibrahim Kiganda and his assistant, Ruth Chebet. Located at the base of Mount Elgon, Sironko Station serves as the collection point for cherries sourced from some of the mountain’s most remote communities, including Yilwanako, Mayiyi, Buginyanya, Bushiyi, Makali, Bukalasi, and Sipi. Unlike the traditional homestead processing common in Elgon, this centralized approach allows for precise control over processing variables—essential for refining best practices and reshaping the global perception of Ugandan coffee.

As part of Mountain Harvest’s annual Innovation Series, this lot represents our commitment to exploration and progress. Each season, we dedicate a portion of our production to experimental processing, allowing for a cycle of testing, learning, and refining. These experiments often begin with small batches, undergo quality feedback and adjustments, and then scale up to production lots. More than just developing new flavor profiles, this process empowers Uganda’s next generation of coffee professionals, giving them ownership over research, methodology, and market feedback. Too often, coffee processing research is based on Latin American models that don’t fully translate to Uganda’s unique context. Through our Innovation Series, young Ugandan professionals gain the tools to conduct and analyze research, ensuring that best practices are shaped by those on the ground. The result? New techniques, exciting flavors, and truly exceptional coffees for our roasting partners.

Process
A meticulously crafted lot from the Buginyanya and Mayiyi farmer groups, Sironko NAF-PK1 Yeast represents the intersection of tradition and controlled fermentation innovation. Only cherries meeting 80% cherry board selection with a Brix reading of 17% are selected, ensuring the highest quality raw material.

This lot undergoes 120 hours of anaerobic fermentation in sealed barrels, submerged in a carefully prepared PK1 yeast dilution, enhancing complexity while maintaining balance. After fermentation, drying follows a two-stage approach—first, sun-dried on raised beds for 3-5 days, allowing initial moisture loss, then slow-dried in shade until reaching 10.5% moisture. Once dried, the coffee is transported to a temperature-controlled warehouse, where it rests to ensure optimal flavor development.

This lot is the result of our partnership with Novensis, a yeast and bacteria company dedicated to advancing coffee fermentation. Through this collaboration, we are not just exploring new profiles—we are shaping Uganda’s future in coffee processing, ensuring that every experiment is rooted in both scientific rigor and respect for origin.

The result is a structured, fruit-driven cup, showcasing clarity, sweetness, and depth—qualities that earned it 4th place in the 2025 Africa Taste of Harvest (Natural Category). This lot exemplifies Mountain Harvest’s commitment to fermentation precision, pushing the boundaries of Ugandan coffee while keeping balance at the core of every experiment.