Processing Coffees

The coffee bean that we roast, grind and drink is a seed that originates at the center of the coffee fruit (or cherry) that grows on coffee plants.

Most coffee beans grow in pairs, each forming half of the center of the coffee cherry, but some cherries have only one seed, which is known as a peaberry.

Surrounding the coffee bean are numerous protective layers that must be removed after harvesting, and the method of this removal also impacts the quality and flavor of the resulting roasted coffee in complex ways.

Wet Processing (Washed coffee)

Wet processing or washing coffee, a predictable and mostly machine driven method of removing the outermost protective layers of coffee, starting with the outermost cherry hard skin. With the outer skin removed, the coffee cherry’s pulp or mucilage, is exposed. Mucilage is a sticky, sweet material similar in consistency to the interior of a grape.

In wet processing, the de-skinned coffee is floated in fermentation tanks with enzymes and bacteria that dissolve the pulp. The coffee is next rinsed and then allowed to dry on sun decks or in mechanized dryers depending on the method most appropriate for each origin. Coffee in this state is called parchment, which is the name of the final hard-shelled hull that contains the interior bean(s). Coffee is sometimes stored in its parchment state for many months, but usually proceeds directly to the next stage of processing called dry milling, where both the outer parchment hull and inner paper-like silverskin are removed. Beans are then typically polished and sorted by size and quality grade for packaging in jute sacks.

Pulped Natural (Semi-washed)

In this hybrid method of processing used primarily in Brazil and Indonesia (some in India), the outer cherry skin is removed mechanically and then coffee is allowed to dry with the sticky mucilage still attached, creating some of the sugar fermentation characteristics of natural processed coffee in a more controlled environment, but with similar risks of not managed carefully.

The mucilage hardens as it dries and is also removed in the dry milling phase.

Natural Processing (Naturals)

Natural processing is the oldest method of coffee processing, where coffee bypasses wet processing completely and is allowed to dry whole in the coffee cherry pod. While drying, sugars in the interior mucilage ferment causing complex chemical reactions with the interior coffee bean(s). Natural processed coffees often have more pronounced fruit, berry and citrus-like characteristics as the result of this intensified internal chemical reaction.

Although less complex and requiring far less water than wet processing, which is sometimes a scarce resource in coffee growing regions, controlling the fermentation process to obtain a consistent end-product green coffee is extremely difficult. Differences in sugar concentration and types, drying temperature, time and other chemicals naturally present within the coffee create a processing environment with limitless variables that must be managed by the farmer. If not controlled, natural processed coffees easily over-ferment, which creates excessively fruity, vinegar or worse tastes of left unchecked.

Dry natural coffees (confusingly also called “cherry” in India) continue to the dry mill where the external dried pod, internal mucilage and hull are removed at the same time.