What does it mean if your coffee glows under UV?
Quality Control. It’s intricately built into the fabric of speciality coffee, a part of the daily routine for roasters, baristas, importers, exporters, and farm managers. After all, how can we ensure the quality that speciality is built on if we don’t control it?
Putting aside the slightly ludicrous idea that we can somehow control the quality of a natural product that is prone to the whims of the ecology it grows in, let alone all the hands it passes through to get to the cup (frankly it’s a miracle coffee tastes so good so frequently!). The largest issue with QC is the binary nature of its application.
Raw Material Timor-Leste operates a number of washing stations in remote areas of the district of Ermera. Infrastructure here is lacking as a rule, and the climate in recent years has made efficient processing a challenge, specifically in regards to drying.
How the parchment is dried is crucial to ensuring both quality and shelf life. In 2022, we found that the coffees landed exceptionally better than the preship samples. However, a month later the washed coffees had not only faded, they had dropped off a cliff of quality. Complex acidity and sweetness had faded to papery and woody notes seemingly overnight. A tell tale pointer to why was revealed in the QC.
As a matter of course, we conduct a UV analysis.
The number and state of the glowing beans can tell us things about the history of the coffee's processing. For instance, bright spots often indicate pulper damage. In this case, the coffees were devoid of the bright glowing beans often associated with fermentation issues and often indicate a shorter shelf life, and instead exhibited an intense mottled glow across the whole bean.
This mottled glow can come from two major sources;
Intense heat during the initial drying
Heat build up during the milling process.
The first was easier to diagnose and correct, it turns out it was an unusually hot year and the beans were being laid out to dry at the peak of the day with no shade. Naturals and Honey processed beans can handle this as they have a built in heatsink to protect the bean from this exposure, but the washed coffees in their parchment do not. This explains why the washed coffees exhibited faster fade than the naturals. The solution was a change in process and shade netting for the washed drying beds, practical infrastructre changes that were low risk and easy to implement.
The second reason was harder to diagnose, whilst training on the UV process at our farm in Colombia we micro-milled some coffee for extended periods to see if there was any change in the UV. The longer periods created more heat and the beans exhibited identical edge glow levels to the beans from Timor-Leste.
An exploration of the milling revealed that a different mills was used for that harvest. Specifically, a commercial mill that runs continuously and as such gets very hot and is not designed for speciality lots. The solution? Build our own mill… in the future, but in the meantime work with another mill. Following seasons crops have landed with far lower edge glow and much longer shelf lives. The impact here is a growing market for Timorese coffee allowing us to purchase more at sustainable prices.