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The devil’s in the detail in coffee processing

The coffee production process is often referred to as an art, and certainly at the final stage, the work of a talented barista can be described as such. At the other end of the process, however, it's more of a science. Indeed, when it comes to growing and processing the perfect product, there really is no detail too small to be considered, especially if the focus in on quality, rather than quantity.

Of course, there are no fixed rules for growing the perfect bean. For instance, while Robusta may be grown as low as a couple of hundred metres above sea level (or even at sea level itself), Arabica can be grown further up. Similarly, while some crops need relatively neutral soil and climatic conditions, other plants will be more tolerant to a harsher growing environment.

At the processing level, however, some things are the same the world over – whether it's in Central America, Africa or elsewhere. Here, failure to work meticulously and follow tried-and-trusted methods can result in entire crop loads being ruined.

Take the processing of coffee cherries, for example. In countries where water is scarce, these are often processed using what's known as the dry method, and again, failing to pay attention to the details can spell disaster for growers. After spreading their picked cherries out in the sun, the grower must rake and turn them right throughout the day without fail and then, when the sun goes down, cover them. Forgetting to cover them for just one night can cause them to get soaked, potentially ruining the whole year's crop. After this and only when the moisture content of the cherries reaches precisely 11 per cent can they be moved to the warehouses for the next stage of the process.

The method is just as exact in countries where rainfall is more reliable and so where the wet method of processing is used. In fact, this latter technique is arguably even more complex, requiring even more care to be taken. Again, carelessness, forgetfulness or any deviation from tried-and-trusted methods can cost the grower dearly.

In the wet method, the cherry pulp is removed almost straight away, with water used to wash away the outer layer and sort the mature from the immature beans. By leaving the wet beans to ferment for a maximum of 48 hours (again, it's all about keeping things precise and consistent), the outer layer of skin is removed naturally, meaning the beans can then be washed a final time before being dried either in the sun or in specialist dryers.

Whether the cherries have been processed by the wet or the dry method, they then need to be graded and sorted before they can be exported, and here meticulousness is important for another reason. While inaccurate grading will not ruin the crop, it can affect the quality of the final product and, just as importantly, mean that the buyer doesn't get what they are paying for.

To ensure neither of these things happen, the coffee beans are sorted according to size in a process known as screening. Here, they are passed through metal sheets filled with holes of a specific size, meaning beans above this size are retained and smaller ones discarded. Inevitably, a few rogue small beans as well as some oversized beans will slip through and end up being exported in the same batch, but, as a rule, exporters aim for a consistency rate of 95 per cent so as to ensure their clients get what they pay for and the end consumer enjoys the perfect cup of coffee. 

It's worth noting that this is just a small stage of a long and complex process. Indeed, the actual cultivation of the coffee plant is just as complicated – if not more so! – meaning that from bean to cup, no detail is overlooked in the pursuit of perfection.