Cold Wash Process

Once coffee fruits are harvested, the seeds contain a lot of moisture and need to be dried to a level where they can be stored without spoiling. Ideally, this moisture content should be around 10-12% for most varieties of coffee. There are various methods for drying coffee, each affecting the flavor and characteristics of the final product.

In the early 2000s, there was a widespread belief that washed coffee, with their cleanliness and variety characteristics, was superior in quality compared to naturally processed coffee, which was often seen as lower quality due to its earthy flavor resulting from the processing method. However, in the past decade or so, there has been a significant shift in perception. With greater knowledge and understanding of fermentation techniques in coffee processing from the 2010s onwards, this perception has changed dramatically. Controlled fermentation processes, the use of specific yeast and bacteria strains, and a willingness to explore and push the boundaries of coffee flavor profiles have become prevalent in the industry's development. And with all the mucilage and nutrients available for fermentation, the natural processing methods have been the primary method to drive this development.

 

 

“The delicacy, fragility and inherent natural qualities of appreciated varieties are regaining popularity, and washed processed methods are quickly becoming the medium to showcase great craftsmanship in the field and to celebrate unique varieties”

 

 

However, extensive processing methods have seen a lot of coffees lose their unique variety qualities, resulting in a market flooded with very similar flavor profiles. Now, there seems to be a shift in this trend. The delicacy, fragility and inherent natural qualities of appreciated varieties are regaining popularity, and washed processed methods are quickly becoming the medium to showcase great craftsmanship in the field and to celebrate unique varieties.

We value innovation in processing methods, but we also believe in allowing the true essence of coffee to shine through without fermentation. That's why we've developed a unique processing method called the 'Cold Washed Process.' This method respects the tradition of the washed process while embracing innovation.

 

Cold Washed Process 

Cold Washed Process accentuates the inherent beauty of our coffees and showcases our dedication to preserving their natural qualities. This processing method minimizes interference with the coffee’s innate characteristics while enhancing its existing attributes. First, we subject the coffee cherries to an initial cold storage period of 48 hours at 8°C. This gentle chilling process preserves and intensifies the coffee’s aromas without inducing fermentation, thereby safeguarding its natural taste profile. Subsequently, the cherries undergo thorough washing and drying at low temperatures in a pressurized, rotating tumble dryer. This meticulous drying procedure ensures uniformity, resulting in a clean and crisp final product. Importantly, our cold washed method adheres strictly to the principle of purity. There are no additives, no introduction of yeast or bacteria, and no active fermentation involved—just coffee in its purest form, allowing its inherent qualities to shine through.

 

The preservation, as well as the intensification, of inherent aroma compounds with this processing method, has been continously verified by GC-MS analysis results. The tendencies show an average increase of intensity of variety unique aromas by 60-70%, while the average preservation of variety unique aroma compounds is above 90% with this processing method, compared to 84±3.6 for the average washed coffee and 67±4.1 for the average naturally processed coffee. It was measured through GC-MS analysis of the green coffee once pre-drying and once post-drying to see the loss of individual aroma compounds during the drying process.

 

The apparent reason for the greater levels of preservation and intensity of inherent aroma compounds in cold washed coffees, is the retardation of the germination at the low processing temperatures, which allows to retain compounds (free amino acids, fatty acids, oils, sugars, etc.) that acts as precursors for aroma compounds during drying and roasting.

 

Another factor is the absence of active fermentation. Fermentation involves microbial activity that can metabolize certain compounds present in the coffee cherries, including sugars, acids, and other organic compounds. This microbial activity can lead to the breakdown of some inherent aroma compounds through various enzymatic and chemical processes. Additionally, fermentation can promote oxidation reactions that may also contribute to the degradation of inherent aroma compounds. That being said, well-executed fermentation in coffee can be very desirable - introducing a wide range and intensity of new non-inherent aroma compounds to the aroma structure of coffees providing another type of quality. Fermentation also increases the acidity of the coffee, which can be a highly desirable trait, contributing to the brightness and liveliness, balancing sweetness and enhancing overall complexity - a great addition to the diversity of quality coffees on the marked. Fermentation has also proved a great tool to lift the quality of low-quality coffees. However, with the cold washed process, we focus on the genetically inherent aroma compounds, which are typically lost or diluted during fermentation.

 

At the same time, we typically experience that coffees that have been ‘cold washed processed’ have a higher level of perceived sweetness. This is linked to the aroma compounds being synthesized from the retained aroma precursors, and the already existing aroma compounds in the green beans, are esters associated with fruity sweet flavors and terpenes associated with flavors of sweet florals, which gives off a high perception of sweetness.

 

Some of the key aroma compounds we see in higher concentrations, which are either directly preserved or synthesized to a greater extent, as a result of the cold washed process, include:

 

Esters

1. Methylbutyrate: Contributes to fruity aromas, often described as having notes of strawberry or pineapple.

2. Methyl acetate: Known for its sweet, fruity aroma, methyl acetate adds complexity to the coffee's fragrance.

3. Isobutyl acetate: Responsible for imparting floral and fruity notes, such as those reminiscent of jasmine or apricot.

4. Ethyl acetate: Contributes to a sweet, fruity aroma with hints of pear or banana.

5. Isopropyl acetate: Similar to ethyl acetate, isopropyl acetate adds fruity notes.

Terpenes

The most predominant terpene:

1. Limonene: Limonene is commonly found in citrus fruits and contributes to a citrusy aroma. In coffee, it can add a hint of lemon or orange notes to the aroma profile.

Other terpenes that may be present in smaller quantities, but still significantly impact aroma:

1. Linalool: Linalool is known for its floral aroma and is found in various flowers, including lavender. In coffee, it may contribute to floral notes.

2. Geraniol: Geraniol has a rose-like aroma and is found in roses, geraniums, and other flowers. In coffee, it may add floral and fruity undertones.

3. Verbenol: the presence of verbenol may contribute to the overall complexity of coffee's fragrance, adding a green-woody florality.

Aldehydes

1. Furfural: Contributes to the sweet, caramel-like aroma characteristic of roasted coffee.

2. Benzaldehyde: Benzaldehyde adds a nutty or almond-like aroma to coffee.

3. Vanillin: Often associated with the aroma of vanilla. It contributes to the sweet, creamy, and sometimes floral notes in coffee.

4. Hexanal: Contributes to green, grassy, or leafy aromas in coffee, particularly in green coffee beans.

5. Nonanal: Has a fatty and citrusy odor with a hint of orange or lemon.

Ketones

1. 2-Heptanone: Contributes to fruity and buttery aromas.

2. 2-Nonanone: May contribute to floral and fruity notes in coffee.

3. 2-Undecanone: Can add green, grassy, or herbal notes to coffee, particularly in green coffee.

It should be noted that, overall, the aromas in coffee are a result of the interactions between the coffee plant's genetics, which are the ones we are interested in retaining with this technique, but also the growing conditions (terroir) and roasting technique. Additionally, the overall aroma profile of coffee is influenced by the interactions of various aroma compounds, creating a complex composition of aromas.

It is our desire here at Poma to continue to explore new ways such as new processing techniques to improve coffee quality.