Why Funky Coffees Taste the Way They Do

We’ve talked about what funky coffee tastes like, let’s get to the bottom of why funky coffees taste the way they do!

It All Starts with Fermentation

Every coffee cherry goes through some kind of fermentation after picking. The sticky layer of mucilage on the bean is loaded with sugars (glucose, fructose, sucrose). Yeasts and bacteria love sugars,  it’s their favourite food.

As they feed, they produce a cocktail of by-products: acids, alcohols, esters, and other aromatic compounds. Some of these bind to the coffee seed itself, and others get trapped in the parchment and transfer during drying. The result? A profound impact on how the coffee will eventually taste in the cup.

Why Funky Coffees Are… Well, Funkier

In most “safe” washed coffees, fermentation is short and controlled,  just long enough to loosen and clean the mucilage. Think of it as the “rinse cycle” of coffee processing.

But in experimental or extended processes, that window is stretched from hours into days. This is where things get interesting:

• Yeasts (especially Saccharomyces cerevisiae and wild strains) pump out fruity esters like ethyl acetate and isoamyl acetate, which give those big tropical fruit, banana, or wine-gum flavours.

• Bacteria — mainly lactic acid bacteria (LAB) and acetic acid bacteria, produce lactic acid (smooth, creamy tang) and acetic acid (sharp, vinegary edge).

• Extended Time means more secondary metabolites: phenols, aldehydes, higher alcohols. Some create funky berry-wine notes; others can push into boozy, fermenty territory.

• Oxygen Levels matter too: anaerobic (low oxygen) tanks tend to suppress some bacteria and boost different yeast pathways, leading to punchy, winey funk. Aerobic ferments bring brighter, more volatile aromas.

It’s just like bread dough, a short ferment is clean and mild, but let it go longer (or use a sourdough starter), and you unlock depth, character, and wildness.

The Role of the Producer

Producers like Pil Hoon Seu (who grew and processed our current funky lot) don’t just leave this to chance. Experimental processing has become a fine-tuned craft:

• Selected Yeast Strains are often pitched into the tank, just like in winemaking, to guide flavour.

• Temperature Control ensures consistency: warmer ferments run faster and funkier, cooler ferments preserve more delicate aromatics.

• Fermentation Vessels matter: sealed stainless tanks, clay amphorae, or even plastic barrels all create different microclimates. Amphorae, for instance, allow slow oxygen ingress, adding depth.

• pH and Brix Monitoring helps producers know when to stop the fermentation before off-flavours creep in.

This is where coffee really becomes art + science: centuries of tradition meeting microbiology and chemistry.

Why It Matters in the Cup

All those compounds formed during fermentation don’t vanish in roasting — many are volatile but survive long enough to dissolve into your brew water. That’s why:

• Your cup might smell like tropical fruit salad.

• You might taste red wine, balsamic tang, or ripe berries.

• You sometimes catch that unmistakable fermenty, boozy edge.

And this is why brewing with a lighter hand (as we covered in Part Two) helps: a lower brew ratio or shorter extraction can emphasise the fun esters and acids, while keeping the heavier fermenty compounds in check.