Coffee Wine Processing Method? What Are Coffee Green Bean Processing Methods? Coffee Anaerobic Fermentation Principles

The Evolution of Coffee Processing

As coffee has reached ever more drinkers in recent years, we've watched processing methods evolve in parallel: from the original washed and natural processes, to honey processing and wet-hulling, and on to the wine-style fermentation and carbonic maceration methods that have taken off recently.

Pressure Honey Processing: Anaerobic Fermentation Goes Mainstream

Pressure honey processing is what's currently everywhere — anaerobic processing, also called oxygen-free fermentation.

This is pressure honey processing, run much like winemaking: the depulped beans, still coated in mucilage, are sealed together in stainless-steel tanks to ferment. The pressure inside the tank slows fermentation dramatically, letting the coffee build more sweetness and a wonderful, distinctive acidity — the ultimate goal of the method.

Carbonic Maceration: Borrowed from Wine

Carbonic maceration is a technique from winemaking in which whole grapes are placed in a carbon dioxide atmosphere to create an anaerobic state. Even without added yeast, the fruit converts its own sugars into alcohol, developing special aromatics. Wines made this way show soft aromatics, a rich mouthfeel, and stable color.

Applying It to Coffee

So how does this translate to coffee?

Step 1: Vessel Selection and Temperature Control

Depulped coffee goes into stainless-steel containers. Why stainless steel? As Sasa explains, it keeps the flavors clean. Different temperatures are then used to govern the pace of the reactions.

Step 2: Managing Temperature

The containers are held indoors where temperature is easier to control. The producers found that if you want more complex acidity, hold the temperature at 4–8°C; if you want higher sweetness, hold it at 18–20°C.

Step 3: Sealing to Build Aromatics

Sealing the fermentation tanks allows more aromatic compounds to develop.

Step 4: Adding Carbon Dioxide — The Crucial Step

This is the decisive step. Carbon dioxide is denser than oxygen, so injecting it pushes the air out and plunges the coffee into an oxygen-free environment. Without oxygen, the breakdown of sugars in the mucilage slows, and the pH falls more gradually.

With carbon dioxide's help, a fermentation run at 22°C stretches out by 3 days — and at lower temperatures it can last even longer. The payoff is a cup with less astringency and none of the vinegary harshness.

FrontStreet's Panama Hartmann

FrontStreet's Panama Hartmann is processed exactly this way. The wine-style fermentation gives the beans a rich, vinous aroma that makes a real impression.

FrontStreet's Pour-Over Recommendations

Recommended parameters:
V60 / 90°C / 1:15 ratio / 2-minute brew time

Flavor profile: grapefruit, low acidity, rich fermented wine aromatics.

FrontStreet Coffee Recommendation

If anaerobic processing intrigues you, FrontStreet's Colombia Sidra is the most vivid expression of it in the lineup. Grown at 1,650–1,800 meters on Colombia's Borderline Estate — the same source whose Sidra carried 2022 World Barista Champion Anthony Douglas to the title — this competition-grade variety receives a double anaerobic natural treatment: whole cherries are sealed in tanks and injected with carbon dioxide to drive out the oxygen, slowing sugar breakdown in the mucilage and letting the beans build extraordinary sweetness, complexity, and a silky, dense texture before finishing on raised drying beds.

Roasted medium-light, it shows jasmine and citrus on the dry fragrance, then passion fruit, blueberry, grape, and apricot in a dense, juice-like body, with a faint spice in the mid-palate and a lasting cocoa finish. It suits pour-over, espresso SOE, and cold drip alike — and an iced pour-over brings out an especially fresh, smooth grape-juice character. For a gentler take on innovative processing, the FrontStreet Costa Rica Mozart uses raisin honey processing — cherries pre-dried on raised beds for at least three days before the skin is removed with 100% of the mucilage retained — yielding osmanthus, pineapple, and raisin aromatics with a white-wine texture and beautifully balanced acidity.