Wet Processing

One of Mountain Thunder's (2) 40 bag per hour ecosystem pulper


Washing coffee is a way to stop fermentation of the slippery mucilage coating once the cherry skin has been removed. This dry fermentation by natural yeasts causes the bean temperature to rise and turns the coffee towards a bitter flavor. Wet milling and water-washing stop this process from happening, which smoothes out the flavor of the coffee. In Kona, all coffee has traditionally been wet milled and Mountain Thunder continues this tradition, and takes the processing to the next level.

Mountain Thunder's wash basin where cherries are separated.


Cherries are sent through a soaking pool, where some of the beans will float and the rest of the beans will sink. Then the heavy, sinkers will be sent to the pulper to be pulped. The cherries that float will make a “C” grade coffee, which will be separated from the rest of the incoming cherries. Then, the cherry skins are removed using the pulper pictured above at a rate of 4,000 Lbs per hour. The pulped coffee beans are sent into the Criba, a piece of perforated sheet metal wrapped around a drum.

Mountain Thunder's Criba. This item sorts away over-ripe and under-ripe beans from good beans.


The beans are sent through the center of the Criba and the good beans fall through to a trough below the cylinder. This coffee that falls through the Criba will be classified as the “A” grade parchment coffee. This coffee will be very clean and have an even color, which helps during the drying process. The un-pulped beans or beans which have not fully been pulped, make their way as they are agitated toward the end of the cylinder where they are collected to make a “B” Grade of parchment coffee. The next step, once we have created an “A” grade parchment coffee is to wash this wonderful coffee. At Mountain Thunder we do a washing and a fermentation process to take away the slimy musilige coating. We do a washing by fermenting the beans