Our final measurement involves looking at the coffee under a UV light. Beans that are high in moisture, unripe, or defective will light up brighter than the rest. The UV light can even identify defects that aren’t visible yet, like phenolic beans or fungi. These types of defects can spread in transit and eventually affect an entire 60 or 70kg bag of green beans, which is why this step is incredibly important.
UV luminosity usually correlates with our other measurements. For example, if UV is high and moisture and water activity both low, we know to re-calibrate our equipment and check again. If the results still differ, this could be an early sign of moisture problems.
Spot the defect