The step of resting parchment in coffee processing
December 23, 2022
There are a multitude of steps involved in processing coffees, with each having its part to play in contributing to the final quality of the coffee that is produced. While a good many parts of this long process has come to the attention of coffee drinkers, such as the value add of the duration and difference in processes such as anaerobic fermentation, or the importance of picking only similarly fully ripened coffee beans, there are also other equally important aspects that have gone under the radar of shared knowledge.
Among them, is giving freshly processed coffees a sufficient period of rest and quiet.
To Put at Rest
In Spanish, reposo stands for “rest”, and is the activity of storing parchment coffees after the initial stage of processing. The widespread usage of this term stems from the fact that the majority of the world’s coffee production comes from South America, and these Latin American producers are generally proficient in Spanish. However, reposo is practiced beyond just these regions – if any producer wants to produce good coffee, it is important for the coffee to have had sufficient and proper rest.
Resting coffees requires a space that has been specially set aside for this purpose: big enough to store multiple batches of harvest, sheltered and protected from environmental influences in a dark and clean place, in a dry environment conducive for this stage of rest.
To be ready for this process, the coffee beans must have sufficiently low moisture levels to ensure that the coffee beans will not turn bad.
From when it is freshly processed, where moisture levels are around 44%, some form of natural drying needs to occur (usually as they are being placed in the porous polypropylene or burlap bags) until moisture levels in the coffee reach 12-13%. At this point, the coffee beans can then be properly stored in the warehouse to rest.
To get to these moisture levels quickly, some farmers have also tried utilising drying beds to bring the coffee beans to a 12-13% moisture level. Yet, despite doing so, it was found that a same overall duration of rest was required for the flavour profile of the coffee beans to fully take shape and to taste good, and there were little benefits to expediting the initial drying steps!
The Beauty in Resting
At the point when coffees have been processed into parchment, the moisture content in the exterior of the coffee bean is usually higher than its interior, due to the nature of processing coming into contact with only the exterior of the bean’s cell structure.
However, during the coffee bean’s time in reposo of about 8-12 weeks, its composition normalises, distributing moisture content evenly across the coffee bean. An even moisture content enables effective heat transfer through the entire coffee bean during the roasting process, ensuring that roast levels in the coffee are consistent from inside to out. (Here, water activity slows down as well).
Depending on the complexity of the fermentation and density of the coffee bean, the necessary time required for reposo may vary – the more chemically complex, or the more dense and closely packed moisture in the coffee bean, the longer it may take for the coffee compounds and moisture levels to stabilise, increasing resting time. It is thought that reposo helps to create a consistent and even flavour profile in the coffee.
Additionally, coffees that have been sufficiently rested often retain its quality for longer periods, and are less susceptible to taking on odours of its surroundings during transportation and storage.
On the flip side, coffees that are taken out from rest very quickly have been seen to age rapidly during shipment, appearing as a very different coffee when it arrives in the hands of the coffee roaster. Sometimes, this takes the form of an unpleasant green taste even after roasting!
Reposo and the Supply Chain
Green coffees are kept in their parchment state until export. In the parchment, a layer of air is retained between the coffee bean and parchment, and the coffee is protected from taking on excess moisture due to the non-permeability of the parchment layer, preserving the coffee quality and flavour for an extended period while still being held at rest.
Only when a buyer places an order, will the green coffees with parchment then be taken out to be dehulled, before being packaged and sent for export to its buyer.
In theory, this supply chain is perfectly complementary with the practice of reposo. However, depending on the time that an order is placed, there is some variance in the duration at which a coffee is rested. With our understanding of reposo, as long as orders are not taken out from this phase to be dehulled, packed and delivered too hastily from when the coffee processing is completed, these two simultaneous actions – reposo and taking of orders from buyers – pretty much work in tandem, ensuring that our coffees get their well-needed rest before arriving on our shores to be roasted and enjoyed.