Coffee Damage under UV Light


Coffee Damage under UV Light, originally uploaded by sweetmarias.

Ultraviolet light is useful to see problems with coffee like mold and
bacteria, but these are things that affect low grade lots that are
already quite damaged. However, when I suspect drying problems with
coffee, I check it out anyway. Some recent Sulawesi wet-hulled lots
have been very surprising under UV light, and in general UV shows the
problems with the wet-hull process overall (although our Blue Batak
Sumatras fare well under UV light. This was a surprise. An Ecuador
Cariamanga lot with a nice cup, but some odd off notes cropping up
way too often. The green coffee loots PERFECT. But under UV light,
small nicks, little marks were I suspect the pulper scraped against
the coffee seed due to misadjustment. Then in fermentation the
damaged areas are in contact with mucilage and bacteria, rather than
being protected by the parchment layer. The result is some off cups,
but mysterious since there was little clue under normal light. I
could not get the coffee to "light up" completely under UV for the
photo so the arrows assist in seeing the glowing areas, and then the
little pulper kiss marks can be seen.
--
-Tom