Welcome back to our coffee processing series, where we explore the initial stages of a coffee bean’s journey from seed to cup.
Advancement in technology has allowed producers to expand their research capabilities and develop new, interesting coffee production methods whilst keeping cup quality central to their approach. In this week’s post, you will be introduced to some of the emergent post-harvest processing methods that have been gaining popularity amongst coffee lovers. Let’s begin!
Recap: what is coffee processing?
Coffee processing is one of the initial stages in the coffee beans’ journey from seed to cup, in which producers remove the outer layers of the coffee cherry to expose the green coffee beans that we then roast. Processing has a great impact on coffee flavours and bean quality, which is why Sam, our Head Roaster, always takes processing into account when curating the beans for our signature house blend, single origin espresso and single origin coffees for pourover.
To many people’s surprise, there are many similarities between coffee and wine, including species/varietal classification, sensory attributes and more: the similarities have been tested and proven by one of the most respected palates in Asia.
In addition to the traditional processing methods (i.e. natural, washed and honey processing), producers are now developing contemporary processing methods inspired by the characteristics of wine, and the steps taken in winemaking and spirit distillation (e.g. whisky and rum). Today, we will be introducing you to three of these methods.
Inspired by the strong, fragrant and fermented cup profiles of wine and the use of raisins in making certain types of wine (e.g. Amarone), winey process is a processing method in which coffee cherries are left to over-ripen, dry and then ferment under sunlight.
The winey processing method is similar to natural process: during the day, the beans are laid on a surface to dry under sunlight, then transferred into plastic tubs for storage at night. While producers repeat the steps above for two weeks to achieve a natural coffee, the winey process requires 30 – 60 days of the procedure: this is to make sure fermentation takes place within the coffee cherries. Once the cherries start to resemble raisins, they are then depulped with a depulper machine and then dried until the water level drops to 12-14%. The final result is a strong, fruity and wine-like cup profile.
Inspired by the carbonic maceration method used in fermenting grapes for winemaking, carbonic maceration processing is achieved by fermenting washed coffee in a sealed environment with limited or no oxygen, at a fixed temperature for a certain period of time. The carbonic maceration method allows producers to monitor different parameters (e.g. temperature, humidity, pH and more), meaning producers can better control over the flavours of their coffees. For instance, producers can choose to enhance the acidity of a coffee by fermenting the beans at 4 to 8 degrees Celsius, or to enhance its sweetness by fermenting it at a higher temperature at 18 to 20 degrees Celsius. The result is coffees featuring a wide range of flavours, ranging from dry and vinegary to bubblegum and banana.
Green coffee beans are known for their absorbent nature. Traditionally, green beans are to be stored away properly from anything giving off strong aromas and flavours, so that they can be roasted and brewed to become cups of delicious coffee.
However, the trending barrel-aged coffee processing method goes against that cardinal rule for roasters around the world: in this method, unroasted beans are deliberately exposed to the remaining aromas of spirits and left to age in barrels used for maturation of distilled spirits. The green beans will absorb the aromas and flavours of the spirit that are brewed in the cask, resulting in unique cup profiles impacted by the different tasting notes.
When experimenting with this particular process method, Kenneth Davids found that coffees that were aged in Pinot Noir casks have the tendency to reflect fruity, oak-like notes and dryness, but they were still more mild than the coffees that were aged in whiskey barrels, which carried stronger and more complex scents. With this method, producers can almost tailor-make cup profiles by selecting a coffee from a specific region and aging it in a casket made of a certain type of wood, used to mature a spirit giving out particular tasting notes.
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