There are a number of experimental processing techniques in coffee , each of which can influence its distinct characteristics.
However, one of the most exciting to emerge in recent years is a technique known as carbonic maceration. Introduced by champion barista Saša Šestić in 2015, it's a fermentation method that involves placing whole cherries in a stainless steel barrel and letting them sit in a carbon dioxide-rich environment.
Carbonic maceration is inspired by winemaking, which uses the process to develop grapes before crushing. As with wine, the extent to which carbonic maceration affects a coffee's flavors is often determined by other factors, such as terroir. However, for roasters, it is often an effective way to promote their brand and differentiate themselves from the competition.
Read on to learn more about carbonic maceration and how specialty roasters can use it to stand out from other coffee brands.
The role of fermentation in coffee processing
Before coffee is ready to be roasted, it must undergo a period of fermentation as part of its processing. Fermentation is the chemical breakdown of a substance by bacteria, yeast, or other microorganisms. While it has existed since the Neolithic, its intentional use in coffee is relatively new.
Fermentation begins naturally when microbes, which exist on virtually every surface, find an entry point into the fruit. This could occur when the cherries are picked or when the skin is damaged while they are still on the tree.
The goal of intentional coffee fermentation is to remove the mucilage from the fruit and seed. Typically used in washed processing, it involves leaving pulped coffee in a tank to ferment until the mucilage surrounding the bean is loose enough to remove. It also occurs in natural processing when the mucilage dries around the seeds.
What is carbonic maceration?
As more is discovered about the role of fermentation in coffee, the door is opened to a wide field of experimentation. Among the most popular discoveries is a process known as carbonic maceration.
Borrowed from winemaking, carbonic maceration is a fermentation technique that first came to prominence in the coffee industry in 2015. Seeking to create a coffee with more aromatic complexity and a lower concentration of acetic acid, champion barista Saša Šestić introduced carbonic maceration when he used it for a Barista Championship-winning coffee.
Together with his collaborator, Colombian farmer Camilo Merizalde, Šestić developed the technique after learning about its use in wine. In wine, carbonic maceration uses the injection of carbon dioxide (CO2) to ferment grapes without breaking the skins, so the process occurs within each individual grape. The initial fermentation is not caused by yeast, but rather occurs intracellularly, or from the inside out.
In coffee , it involves placing harvested coffee cherries in airtight barrels before pumping in CO2 to create a CO2-rich environment. The CO2 allows the cherries to break down different levels of pectin, often producing bright, winey coffees with strong red fruit notes.
According to Šestić, all the flavors and aromatics produced by carbonic maceration have no way to escape. Instead, they are absorbed by the coffee parchment, contributing to a fruity quality in the cup. During the process, they use low temperatures to prevent alcohol buildup.
Once the coffee has reached the desired level of fermentation, the cherries can be processed by washing or drying. (Both processing methods are suitable for carbonic maceration coffee.)
Unlike anaerobic fermentation, carbon maceration can take months to produce coffee with the right flavor. This is because the cherries are left whole when they are placed in the barrels, rather than pulped.
Problems with carbonic maceration
While carbonic maceration can be very controllable and consistent when perfected, it is still considered an experimental processing method when it comes to coffee.
Small changes to a vat of coffee fruit can have a big impact, either making or completely destroying the flavor. Temperature is largely what controls the fermentation process. And getting it right comes down to both trial and error and the grower's skills. A small change could lead to over-fermentation, giving the cherry a very undesirable fermented flavor.
These experiments involve not only greater risk, but also more labor, higher production costs, and require more equipment. This means that carbonic maceration and anaerobic coffees are often more expensive than traditional washed or natural and dry-processed coffees.
Conclusions
Processing is one of the most important aspects of coffee production and impacts flavor, aroma, and quality. This is why many producers seek to improve their processing in pursuit of higher-scoring coffees and more complex flavor profiles.
Despite being a relatively new concept in coffee, carbonic maceration has become popular among specialty roasters. Intrigued by the perceived flavors it can impart on coffee beans, consumers are interested in experimental processing, and carbonic maceration is already a favorite among some.