coffee society journal — fermentation, part one
Here's a surprise: every coffee you've ever tasted was fermented. It isn't a style so much as a stage, the hours between picking the cherry and drying the seed, when microbes (the yeasts and bacteria living on the fruit) eat the fruit sugars and quietly shape the flavor. The only real question is whether that fermentation was managed with care or left to luck. This is the first post in a short series on how it works.
01fermentation isn't optional
The moment a coffee cherry comes off the tree, the clock starts. Yeasts and bacteria that already live on the fruit skin begin eating the sugars in the mucilage, the sticky layer between the skin and the seed. That's fermentation, and it happens whether anyone wants it to or not, in the washing tank, on the drying bed, or inside the whole cherry of a natural process.
So when a bag says “fermented coffee,” it's a bit like a menu saying “cooked food.” The more useful questions are how long, how warm, and how controlled.
02what good fermentation does
Temperature is the big lever. A warm afternoon at a low altitude washing station can push a tank in six hours to where a cool mountain night takes twenty-four. The best producers track time, temperature, and sugar levels the way a baker tracks a sourdough, by habit and with numbers.
03how to taste it at home
Brew two coffees side by side, a washed lot and a natural. The washed one had a short, water-rinsed fermentation, so it's clean and bright. The natural fermented longer inside the whole fruit, so it's jammy, wine-like, and heavier. That difference is mostly fermentation, and once you can taste it you can't un-taste it.
Our bags print the process on the front for exactly this reason. Every lot we buy scored 85 or higher, which among other things means the fermentation was controlled, since flaws like vinegar and ferment funk cost points fast.
04common questions
No. A trace of alcohol forms during fermentation, but it disappears in drying and roasting. A boozy flavor in some experimental lots is an aroma, not a proof.
Longer, oxygen-starved fermentations push big fruity compounds. When it's controlled, that tastes like tropical fruit, but when it isn't, it tips into vinegar. The line between the two is usually a producer paying attention.
No, it's a seasoning, not a goal. Some of the best coffees in the world are simple, precise washed lots. What matters is that someone chose the fermentation on purpose.
taste fermentation done right
Every coffee we roast names its process on the bag, whether that's washed, natural, honey, or experimental, so you can taste the difference on purpose. Roasted to order in Berkeley, CA and shipped within 24 hours.
shop current lots processing 101coffee society · specialty micro roaster · berkeley, ca · est. 2023