For exceptional specialty coffee, sorting during harvesting and processing is of the utmost importance. Even a few low-quality or defective beans can reduce the quality of an otherwise excellent lot.
Ben Weiner, CEO of Gold Mountain Coffee Growers, invests heavily in post-harvest sorting and agreed to talk me through his processes. These stages are implemented on his farm, Finca Idealista in Nicaragua, and also followed by any partner farm of Gold Mountain (something that he tells me benefits both the farm and its customers, as it ensures better cup scores and prices).
Let me quickly mention that his advice is most relevant for washed coffee. For natural and honey processed coffees, some of the stages will have to be omitted – meaning workers must be even more diligent when picking cherries. However, even with these alternative processing methods, following as much of this guide as possible will help you to ensure that only the best beans make it into a lot.
Lee este artículo en Español: Cómo Mejorar la Calidad de tu Café al Seleccionar la Cosecha
Selectively picking coffee cherries: the first stage in sorting. Credit: Ben Weiner, Gold Mountain Coffee Growers
Step 1: Picking
Cherry picking is a long and difficult task: Ben tells me that, on his farm, it starts at 6 am and continues until 2 pm, at which point they switch to other quality control tasks.
Before picking begins, he recommends first inspecting the crop to ensure the cherries are ripe enough. You can use a refractometer to measure their brix, or sugar content. He explains that although there is no “perfect” brix/sugar content, this information provides a reference point. “There is no magic number but rather a range of the right levels,” he emphasises.
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Using a refractometer to measure brix, in addition to a ripeness bracelet, on Finca Idealista. These cherries will need a few more days to ripen. Credit: Ben Weiner, Gold Mountain Coffee Growers
A more affordable way to measure cherry ripeness is through colour. On Finca Idealista, they use this alongside brix content. In fact, they’ve created “ripeness bracelets” that are the exact colour of ripe red cherries.
A word of warning, though: Ben advises that it’s harder to determine ripeness through colour alone when you’re harvesting yellow cherries. He explains that it generally takes experienced pickers to tell when they’re both soft enough and the perfect deep, golden shade.
Ripeness bracelets used to determine if coffee cherries are ripe. Credit: Ben Weiner, Gold Mountain Coffee Growers
When picking, there will also be cherries that are over-ripe or show signs of insect damage. It’s as important to remove these as it is to avoid picking under-ripe coffee. By attaching a bag, which in Nicaragua is called a salveque, to the basket, pickers can put any over-ripe cherries straight into there. Ben recommends that, to ensure pickers are motivated to remove over-ripe or defective cherries, the salveque is also weighed and pickers are paid for it at the same rate as the ripe cherries.
A salveque hangs next to the cherry basket, ready for defective or overripe cherries. Credit: Ben Weiner, Gold Mountain Coffee Growers
Step 2: Sorting on a Tarp
Once the picking is done, Ben advises placing all cherries on a tarp and searching for any stray unripe or green ones. He tells me that, on Finca Idealista, 40 people do this every single day. After all, it only takes one to add an astringent taste to an otherwise delicious (and high-scoring) cup of coffee.
Workers sort coffee cherries on tarps, removing unripe, damaged, and defective ones. Credit: Ben Weiner, Gold Mountain Coffee Growers
Step 3: Removing Floaters
Before fermentation begins, the cherries should be placed in tanks of water to check for defects. Any that float to the top are either hollow or have unhealthy/defective beans and so can immediately be removed. Ben recommends recycling the water to be more environmentally friendly.
Now, the cherries are finally ready for depulping and fermenting (assuming you are wet processing them).
Step 4: Washing Channels
After fermentation, you can use a washing channel to remove defective or low-quality beans. These small channels should feature small wooden weirs or barriers (tablillas in Spanish). The green beans are added to the channels along with running water, and often a worker will use a broom or wooden implement to disturb the layers.
Dense, good-quality beans will sit at the bottom of the channel and be caught by the weirs; low-quality, lightweight ones will float over the top, where they can be caught and either discarded or sold to the local/commodity-grade market. These are often called segundas in Latin American countries.
A washing channel separates dense, high-quality beans from lightweight, low-quality ones. Credit: Ben Weiner, Gold Mountain Coffee Growers
Step 5: Sorting on The Drying Beds
Now that the coffee has been processed and sorted, it’s ready for drying – but there are still quality control steps to be done. Ben recommends that, while coffee dries on the beds (or patios), workers conduct visual inspections. They should look for and remove beans that are broken, chipped, or machine-damaged; have signs insect damage; or are discoloured or too green when wet.
Since all coffee should be regularly moved while drying, these visual inspections can take place at the same time. Similarly, if the coffee is relocated – after the beans have dried a little, Ben moves his lower down the mountain where the climate is warmer – the visual inspection can continue in the new location.
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A worker visually inspects drying coffee, removing any beans do not meet quality standards. Credit: Ben Weiner, Gold Mountain Coffee Growers
Step 6: Cupping
When the coffee reaches the ideal moisture content, Ben recommends cupping it to make sure there are no defects or imperfections. If you notice any, the coffee can then be sorted again.
Step 7: Cleaning Machine
There are a wide variety of machines that, at the final stages of coffee production and processing, can sort through the beans. Ben explains that he uses a machine to remove any extraneous materials: leaves, branches, pebbles, and so on.
Step 8: Density Sorter
Finally, after the coffee has rested for two months, it’s time for the last stages. A density sorter or gravity separator can be used to separate high-density and low-density beans. If you have beans of multiple sizes, however, Ben recommends sorting them by size before putting them through the density sorter; this can also be done by machine.
Step 9: Colour Sorting & Conveyor Belts
The final step is to remove any discoloured beans. Ben explains that this can be done via a machine; however, he argues that it’s even more effective to hire 60–80 workers who will remove the defects on a conveyor belt.
Using this many workers is expensive and time-consuming, but Ben emphasises the value of having clean, high-quality beans without any defects to spoil the lot. The impact of all these steps will be made visible in the cup score.
Sorting coffee on the conveyor belt. Credit: Ben Weiner, Gold Mountain Coffee Growers
In theory, better cup scores should result in better prices paid by roasters, which in turn can pay the high labour costs of all these workers sorting through the beans – adding up to a greater investment in the local community. High-quality coffee can be also financially and socially sustainable coffee.
And Ben tells me that his aim is perfection.
There is no step so small that it can be overlooked when you’re producing and processing specialty coffee. While these quality control steps represent an investment of time, labour, and money, they can also help ensure the best-possible cup of coffee, every single time.
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Written by Angie Molina.
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