Apart from washed, natural, and honey coffee processing methods, there are still some others worth noting.

Wet Hulled Processing

Wet hulled, or semi-washed coffee, is a type of coffee processing that is unique to Indonesia and most often used in Sulawesi and Sumatra. On the one hand, the humid climate here makes the drying conditions difficult – it will take a long period of time to dry out coffee. On the other hand, as farmers want to get their coffee to the market as fast as possible, they have to seek out more efficient and speedy processing methods, thus comes wet-hulled processing.

How wet-hulled processing goes?

The whole process can be divided into 5 steps.

Step 1 Sorting

Picked coffee cherries are sorted by size and density using water.

Step 2 Depulping

Machines remove the outer skin and pulp of the coffee cherry, but mucilage is still left on the seed.

Step 3 Fermentation

The seeds get stored in plastic tanks that retain moisture. The mucilage creates a thick hulk that encapsulates the seeds.

Step 4 Hulling

Machines remove the dried mucilage as well as the thin, flaky parchment from the coffee seed.

Step 5 Drying

The coffee seeds are dried in the sun on drying beds, and the drying time is half of the other processes. Wet hulled beans have a bluish tint.

What's the difference between washed process and the wet-hulled process?

Even though it's easy to get confused, these two methods are, indeed, different – the point is how we get from wet parchment to dry green coffee. In the wet-hulled process, the outer skin is removed, similar to the washed process, but the mucilage – inner-mesocarp – remains on the parchment and is sun-dried. Then the parchment is removed. The swollen white beans enter the second drying phase.

What does wet-hulled coffee taste like?

Wet hulled coffee's intense is not for everyone, but as a single-origin offering, it provides a unique experience for the adventurous coffee drinker. The taste of wet-hulled coffee is not only heavy-bodied thanks to the dried mucilage, but also chocolatey, savory, and nutty – in other words, it combines both washed and unwashed flavor characteristics. And the wet-hulled coffee is perfect for a blended roast.

Even though traditionally producing countries have favored one particular process, an increasing number of farmers are now willing, if environmental and climatic factors allow, to try other processing techniques, due to the demand for specialty coffee.

Anaerobic Process

Anaerobic refers to a new coffee processing method that involves the same fermentation phase as washed coffee, just without any oxygen – all the coffee beans are processed in a fully sealed and oxygen-deprived fermentation tank. Compared to aerobic fermentation, anaerobic fermentation produces distinct acids, like lactic acids, that give the final product a striking flavor. During this process, anaerobic is placed in sealed tanks that are pressurized from CO2 buildup, and then remaining pressure and oxygen are let out using release valves.

The Carbonic Maceration Process

Borrowed from the production of wine, carbonic maceration is a fermentation technique that first came to prominence in the coffee industry in 2015. In wine, carbonic maceration uses the injection of carbon dioxide (CO2) to ferment the grapes without breaking the skins, so that the process happens inside each grape individually. The initial fermentation is not caused by yeast but instead occurs intracellularly, or from the inside out. In coffee, it involves placing harvested coffee cherries in airtight barrels before pumping in CO2 to create a CO2-rich environment. The CO2 allows the cherries to break down different levels of pectins, often producing bright and winey coffees with strong notes of red fruits. Unlike anaerobic fermentation, carbon maceration can take months to produce the right flavor coffee - a coffee with more aromatic complexity and a low concentration of acetic acid.

Coffee processing rarely makes it into the industry headlines or coffee shop discussions, but it's an integral part of crafting the flavor and character of your cup of coffee. If you have more knowledge about coffee processing, you may choose the right coffee beans easily the next time you stand in front of rows of shelves.