coffee society journal — fermentation, part three
“Anaerobic” is probably the most used and least explained word on modern coffee menus. It means one simple thing: the coffee fermented in a sealed tank without oxygen. Take the air away and a different set of microbes takes over, and they produce flavors an open tank never could, like cinnamon, tropical punch, and wine gums. Here's what's actually happening, and how to buy one you'll like.
01what “no oxygen” changes
In an open washing tank, the organisms that like air dominate and the fermentation stays relatively polite. Seal the tank and those oxygen breathers stall while others take over, and those others produce a much wider, wilder range of flavor compounds. Producers often add a one way valve so gas can escape without air getting in, then hold the tank for anywhere from a day to over a week.
The result is usually unmistakable in the cup, with bigger fruit, spice notes, and a syrupy weight. People either fall in love or ask if the coffee has gone off, and both reactions make sense.
02carbonic maceration is the fancy cousin
This one is borrowed from Beaujolais winemaking. The tank is flushed with carbon dioxide before sealing, and whole cherries go in uncrushed. Inside each intact cherry, fermentation starts within the fruit itself, a slow, cell by cell process that tends to produce remarkably candy like, floral results. It's expensive, slow, and easy to ruin, which is why true carbonic lots are rare and priced like it.
03how to buy your first one
Brew them as pour over or drip first. Under milk the wild notes can turn a little odd, but on their own they're about the most fun a cup of coffee can be.
04common questions
The word gets used as one, but the technique is real. Removing oxygen genuinely changes which organisms ferment the coffee and what it tastes like, so judge the cup, not the label.
Tanks, time, and risk. The producer ties up equipment for days and can lose the whole batch if it overshoots, so when it works, it's worth the extra cost.
Maybe. If you love clean washed coffees, start with an anaerobic washed lot rather than a double fermented natural, since it keeps one foot in familiar territory.
when we find a great one, it goes in the rotation
Experimental lots come through our rotating subscription when they beat the classics on the cupping table, and only then. Labels don't win here, cups do.
rotating single-origin fermentation, part twocoffee society · specialty micro roaster · berkeley, ca · est. 2023