Coffee Data Science

Fermenting Indian Robusta Coffee Cherries

By Ashish Rao & Robert McKeon Aloe

Robert McKeon Aloe
Geek Culture


As I got into specialty robusta, Ashish reached out. He had worked on using fermentation to improve the robusta on his farm. He offered to send me a sample of green beans.

The coffee was very different from what I have had before. It had the mouthfeel of robusta without an overpowering bitterness, and the coffee was mildly sweet. So I asked how he fermented the cherries. He shared some diagrams of how he went about fermenting robusta, and he gave me permission to publish them.

First, you must harvest. I love all the pictures, which is why I didn’t remove any steps.

All images uses with permission

Then you pull out all the debris.

Washing comes next. Floating coffee cherries are usually not ripe enough, so you want to remove though.

Another wash and sort followed by a rinse to kill any bacteria.

Ashish tried two types of fermentation: lactic and alcohol.

This starter is used to create the fermentation solution. Two solutions were tried.

The solution with the cherries is places in a tank with a few output monitors to determine when the fermentation is complete.

This one was stopped at a Ph of 4.8, so slightly higher, but the fermentation had gone on for some time.

Afterwards, just a few more simple steps before brewing.

I roasted a sample to a medium roast, and it was a wonderful coffee. It tastes like a more mild arabica with the mouthfeel of a robusta.

Fermentation has led to some interesting arabica coffees, but I’m far more interested on the effects it has on robusta because I crave the mouthfeel of robusta. I’m also curious if such techniques can be used to improve lower grade robusta.

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Further readings of mine:

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Robert McKeon Aloe
Geek Culture

I’m in love with my Wife, my Kids, Espresso, Data Science, tomatoes, cooking, engineering, talking, family, Paris, and Italy, not necessarily in that order.