Coffee Processing

Coffee drying in the sun. Dolka Plantation Costa Rica (Photo credit: Wikipedia)

With the fermentation phase now complete, we move on to the drying phase of processing. You may remember from the first part of this series, coffee processing is broken up into the following stages, as described by both the Queensland Department of Agriculture, Fisheries and Forestry, and my mother, who is very experienced and knowledgeable in these matters:

Pulping
Fermentation
Drying
Parchment removal (hulling)
Roasting
Grinding, strong and brewing

At the completion of Crop to Cup Part 1, we left the beans fermenting in water at stage 2 above. I was a little unsure of how long this may take (72 hours or up to a week), though armed with the knowledge this phase would be complete when the mucilage (slippery outer layer) was easily rubbed away. Daily testing was undertaken, until on day 7 (exactly as predicted by my mother), rubbing one of the beans between thumb and finger resulted in a slightly gritty/pebbly feel rather than a slippery one. Time then to move onto drying.

3. Drying
Once the beans have fermented for long enough, they are required to undergo a final wash and rinse, before being laid out on drying beds. In aid of passing down the coffee loving tradition to the next generation, my son was enlisted to rub off the mucilage, with repeated washes then performed to remove any remaining on the outside of the bean. Agitating the beans and replacing the water over three washes was sufficient to achieve this.

Looking back to our Department of Agriculture guide, the drying process is described as follows:

The beans should be spread out in a thin layer no more than 3 cm thick, stirred three times a day, and be protected from rainy weather. Drying in this way can take 5–30 days, depending on the seasonal weather pattern.

As you can see below, an initial drying of the beans was done on a small towel, before transfer to a drying rack to allow plenty of airflow around the beans. The rack is situated under cover to avoid any weather or dew, however sees the mid to late afternoon sun, which should assist with drying. Given the small crop I am processing, a single layer of beans was placed on the drying bed, with little chance of any mould formation (the reason for stirring daily), though I aim to ensure the beans is are turned regularly.

I hope you will join me in a couple of weeks for the next post in this series, where we will be up to removing the remaining parchment layer and roasting our crop!

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Crop to Cup – Part 1 (dept4.net)
Inside of coffee cherry (pimentona.wordpress.com)
3 Things That Affect How Your Coffee Tastes – Vanessa Tai (materialworldsingapore.com)

While the above title may sound rather exotic, the reality is I have been lucky enough to be given a small, recently harvested crop of beautiful red coffee ‘cherries’. Receiving such a gift carries significant responsibility, and I am determined to process, roast and cup the resulting brew with all the dedication and care I can muster. As regular readers will know, I have been roasting at home for some time now (purchasing green beans online), however to this point have not processed beans straight from the tree. This is a whole new ball game for me. How to proceed?

The first step was a call to my parents, who grow, and therefore regularly process, roast and drink their own crop. Next, an internet search to see what is out there on this topic. I was surprised to find the most helpful instructions on my state government’s Department of Agriculture, Fisheries and Forestry website. For additional reading on the types of processing methods, the International Coffee Organisation (ICO) provides a good summary.

Wet or Dry Processing

Firstly, there are two options, wet or dry processing. What follows in the section below outlines the wet processing method I plan to use, said to “better preserve the intrinsic qualities of the bean”. This method is the one outlined on the state government website, and also the one my parents use.

In the dry processing method, the entire coffee cherries are dried in the sun for approximately 4 weeks (to a minimum 12.5% moisture content), followed by removal of all outer layers around the bean by hulling equipment. States the ICO:

The dry method is used for about 90 percent of the Arabica coffee produced in Brazil, most of the coffees produced in Ethiopia, Haiti and Paraguay, as well as for some Arabicas produced in India and Ecuador. Almost all Robustas are processed by this method.

Wet processing generally follows the procedure outlined below, though obviously on a fairly large scale for commercial operators. As opposed to the dry method, the seed is extracted and fermented first, the drying process then follows, again until the beans reach 12.5% moisture content. The beans are then stored, and the hulling process is completed just prior to export. Again from the (ICO):

The wet method is generally used for Arabica coffees, with the exception of those produced in Brazil and the Arabica-producing countries mentioned above as users of the dry method. It is rarely used for Robustas.

My wet processed micro lot

The wet processing technique I am using involves the following steps:

Pulping
Fermentation
Drying
Parchment removal (hulling)
Roasting
Grinding, strong and brewing

Comparing the method my parents use with those online saw many similarities, with only some of the time frames differing a little in each stage. We will focus on steps 1 to 4, as other posts deal with roasting, grinding and brewing, and in any event, steps 5 and 6 occur independently of the processing method used. Today we will look at Pulping and Fermentation, and return in future posts as my drying process proceeds.

Pulping
Here we are removing all of the skin and pulp (flesh) from the cherry, and extracting both halves of the coffee ‘seed’ from inside, and should occur as soon as possible after harvesting. Be sure to discard any underripe (green) or overripe (black) fruit which will reduce the quality of what ends up in the cup.

Seed extraction in the pulping phase.

This process can either be done by hand (squeezing each cherry between your thumb and finger), or in the bottom of a bucket using a piece of wood to squash the fruit, resulting in the seeds being forced out from the flesh. Adding water will then allow removal of the skins and one other critical element – any floating beans. Good coffee beans will not float, and those that do should be discarded as they are unusable, and will spoil the batch.
Fermentation
There is not a lot to say about this step, apart from the fact it should last anywhere from 18–48 hours to a few days, and involves natural enzymes breaking down the ‘mucilage’ (the outer slippery substance) around the parchment layer.

Removal of floating beans (left); fermentation (right).

Fermentation should be done in a plastic bucket or container (metal may affect the taste), with the entire bean mass covered by water. To test for completeness of this phase, washing a small amount of beans should see the ‘slippery’ coating disappear, resulting in a clean, gritty feel. If so, agitate and wash the remaining beans until he water is clear (again removing any that float), which may take several washes.
Once washed and clean, the beans are then ready for drying.