The processing method used by the coffee farm will have a big impact on the coffee's flavour, body and aroma.
But what are the various coffee processing techniques?
So, let’s start with the basics. The coffee bean is derived from the seed of a cherry like fruit which grows on coffee bushes (with the two main species grown worldwide being Arabica & Robusta). This cherry-like fruit is harvested when ripe and must be processed immediately so they do not waste. From here there are a multitude of processing techniques used to develop distinct characteristics that will impact the final product.
Coffee processing techniques vary by country depending on resources and objectives. Typically, there are four main coffee processing techniques employed;
- Natural (often referred to as Dry) Process
- Washed (often referred to as Wet) Process
- Semi Washed (often referred to as Wet Hulled) Process
- Honey Process
There are however a myriad of variations within each category.
Before we cover the various coffee processing techniques, I think it’s important we cover exactly what the cherry like fruit looks like with all its components, as these characteristics are used in various processing methods to develop distinct characteristics (for example in Natural / Dry processed coffee were the whole fruit is used to allow the sweet flesh of the fruit known as the mucilage to develop sweet notes, unlike Wet / Washed processed coffees were the fruit is washed away exposing just the bean forn processing).
THE ANATOMY OF THE COFFEE CHERRY
Like most fruits the coffee berry is made up of layers;
- Skin - This is protective outer most layer around the fruit (also known as exocarp)
- Pulp - Comprised mostly of water and sugar (also known as mesocarp)
- Mucilage - Inner layer of pulp, sticky & sweet and often referred to as ‘honey’
- Parchment - The hull that covers the seed (coffee beans), when dried becomes parchment paper like
- Skin - The innermost protective layer around the seeds (coffee bans)
- Bean - The bean itself is actually the seed of the coffee cherry fruit. There are actually2 seeds inside.
So now we’ve familiarised ourselves with the anatomy of the coffee fruit, we can now dig in and get an overview of the main coffee processing techniques used, and how these components affect the green coffee beans.
NATURAL (DRY) COFFEE PROCESSING METHOD
The natural (dry) processing method is the oldest way of processing coffee. Typically used in arid countries where water supply is in short supply, such as Western Ethiopia.
In this processing method the cherry like fruits are picked at optimal ripeness. The cherries are left with all the layers completely intact allowing a certain amount of natural fermentation and many enzymatic bi-products are absorbed from the mucilage into the heart of the two seeds (the seeds become the green coffee beans we then roast), which results in an incredibly distinct flavour profile.
Natural (Dry) Method
- Still used in many countries (arid) were water in short supply
- Laid out in large ‘beds’ to sun dry and start fermentation process
- Typically takes 3-6 weeks to complete natural process (weather dependent), complete when circa 10-11% water loss
See our range of Natural / Dry processed coffees here:
Washed (Wet) Method
Wet Hulled (Semi Washed) Method
- Removes pulp from coffee cherry before wet processed (via pulping machine)
- After separation cherries are transported to large fermentation tanks, left for 12-48 hours
- Naturally occurring enzymes will break down the bean, process is complete once the slick layer of mucilage (parenchyma) has fallen off
- Processing Cont’d – Special Prep Processing (Specialty)
Honey Processed Method
- Involves combination of both natural (dry) and washed (wet) processing.
- Anaerobic Honey Processed
- Honey Anaerobic is a process where the beans are hand picked, pulped but not washed and then fermented without oxygen.
- Double soaked / washed
- Double washing is a specialty processing method that improves the quality of coffee. During this process, the coffee beans ferment for an extra, longer cycle, underwater which requires a second wash.
- Carboninc Maceration
- Anaerobic – no oxygen environment
- Carbonic – carbon dioxide rich environment
- Maceration – a more inclusive term than fermentation, referring to microbial metabolism
- Additional Special Prep Processing techniques;
- Black Honey
- Yellow Honey
- Monsooned
- Pulped Rasisin
- Swiss water (decaff)
- Sugar Cane (decaff)