Anaerobic, carbonic maceration, co-fermentation and barrel-aged lots.
Anaerobic and fermentation lots are the most exciting and most divisive corner of specialty coffee right now — cherries sealed in oxygen-free tanks, sometimes with added fruit, yeast or spirits, before being dried as natural, honey or washed.
By controlling oxygen, temperature, pH and time, producers can guide which microorganisms work on the cherry — yeasts, lactic acid bacteria, acetic acid bacteria — and the resulting flavour compounds get absorbed into the bean.
Expect intense, unusual cups: passion fruit, lychee, mango, red wine, whisky, strawberry candy, ripe banana, cinnamon, jasmine, and sometimes a deep boozy or fermented-fruit funk.
Sub-styles on the labels include anaerobic natural, anaerobic washed, carbonic maceration, co-fermentation, thermal shock, lactic ferment and yeast-inoculated lots — every origin on this page experiments differently.
The trade-off is price and consistency. Good experimental ferments are harder to produce and command higher grades. Bad ones taste like solvent. Stick with reputable producers and roasters.