一次搞懂咖啡處理法的差別 Understanding the Differences in Coffee Processing Methods at Once
I prefer sweeter beans, should I choose natural (dry) processed or washed beans? Does honey processing involve adding honey? Does the washed process wash away all the flavors? Coffee processing methods affect the flavor profile, and to understand the coffee in our hands, let's delve into the four major processing methods.
The coffee we drink comes from the seeds of coffee cherries on the coffee tree. The process of transforming these seeds into green coffee beans before roasting is known as coffee processing. It involves several steps to remove the pulp, mucilage, and skin of the cherries, and the proportions of these components affect the taste of the coffee. There are four main coffee processing methods: natural (dry) processing, washed processing, honey processing, and anaerobic processing. These methods alter the sweetness, body, acidity, and flavor of the coffee.
Category 1: Natural (Dry) Processing
Natural processing, also known as dry processing or unwashed processing, is the most traditional and common method that doesn't involve water. Originating from Ethiopia, the coffee cherries are collected and dried in the sun before being hulled. The seeds remain inside. The dried cherries during the extended exposure to sunlight, absorb flavors from the pulp, mucilage, and skin. This process enhances the sweetness and full-bodied richness of the coffee, creating unique aromas.
Coffee producers spread the cherries on drying beds made of patios or elevated drying tables in the sun. Over a period of 3-6 weeks, the coffee undergoes fermentation. The cherries are flipped regularly to ensure even drying and prevent spoilage. During this time, sugars from the cherries and the mucilage attached to the seeds develop flavors and intensify sweetness. After drying, the dried pulp and skin are mechanically separated from the seeds. Naturally processed coffees are juicy and syrupy, making the effort worthwhile.
Winey natural processing doesn't involve adding red wine to the green bean processing. Instead, it refers to a fermentation method similar to the fermentation process of red wine during the processing. The steps are similar to traditional natural processing, but the fermentation period is longer. Coffee farmers select ripe coffee cherries, place them in bags, and let them darken and acquire wine-like characteristics. The cherries are then placed on racks to dry to a moisture content of around 11%. During this process, enzymes in the coffee precipitate, achieving balance. It takes about four weeks for the coffee to undergo fermentation, resulting in increased sweetness and flavor complexity. The flavor resembles the fermentation notes found in red wine, with a distinctive enhancement of sweetness.
Category 2: Washed Processing
Washed processing, also known as wet processing, differs from natural processing. Before drying, all coffee cherries are depulped to remove the skin and pulp. They are then soaked and fermented in water tanks to eliminate the residual mucilage from the seeds. Afterward, the seeds are washed and dried either in sunlight or using machines. Washed processing doesn't wash away the flavors, because the flavors develop during the roasting of the seeds. Although washed processing is fast and efficient, it can lead to environmental waste. The large volume of water used for mucilage removal and washing stations generates a significant amount of solid waste. These stations require substantial infrastructure, technology, and energy, resulting in potentially high operational costs. However, if the water can be reused (often by rebalancing the pH), this method can be environmentally friendly.
Washed processing offers a cleaner and crisper mouthfeel compared to natural processing. It tends to have a lighter body than the natural method and often exhibits brighter flavor characteristics. It possesses the essential acidity found in specialty coffees and distinct fruit flavors, making it easier to discern the different flavor profiles.
肯亞式水洗(Kenya Washed Processing)
The Kenyan washed processing follows the same procedure as regular washed processing. After a natural fermentation period of 12-24 hours, most of the mucilage layer is washed away. The cherries then undergo another 24 hours of natural fermentation before being washed again. Finally, they are soaked in water for 24 hours and then dried to complete the process before warehousing. Kenya's unique double fermentation washed method further enhances acidity and cleanliness. It results in rich berry flavors, a solid body, high sweetness, and vibrant acidity.
Wet-hulled processing, also known as semi-washed processing, is a specific green bean processing method found in Indonesia, particularly in Sumatra. Due to the humid climate, the cherries are initially washed and undergo fermentation. After 1-2 days of exposure to sunlight, the beans, which still have a moisture content of 30% to 50%, are hulled and dried to expedite the drying process. With approximately two more days of drying, the moisture content of the green beans reaches the target storage level of 12-13%. Locally, this method is referred to as "Giling Basah" (wet-hulled processing). As shown in the diagram, the left side represents wet-hulled processing, where there is minimal space between the green beans and the parchment; the parchment is removed before further drying. On the right side, the regular washed processing method shows a significant gap between the green beans and the parchment, indicating that the drying process is completed with the parchment intact.
第３大類：蜜處理法(Honey Processing / Pulped Natural Processing / Semi-dry Processing)
Category 3: Honey Processing / Pulped Natural Processing / Semi-dry Processing
Honey processing is a method that combines elements of natural and washed processing. It originated in Costa Rica. Similar to washed processing, the cherries are depulped to remove the skin and pulp. However, instead of using fermentation tanks, the cherries are exposed to sunlight while retaining the sticky mucilage layer. The term "honey" in honey processing refers to the viscous nature of the mucilage, not the addition of actual honey. The mucilage layer contains a high concentration of sugars and acidity, which are crucial to honey processing. The amount of mucilage left determines the sweetness.
黃蜜(大約保留25%的果膠層) ➞ 曝曬時間較短，果膠層糖分的酵素反應較少
紅蜜(大約保留50%的果膠層) ➞ 曝曬時間略長，果膠層糖分的酵素反應略多
黑蜜(大約保留80%的果膠層) ➞ 曝曬時間最長，果膠層糖分的酵素反應最多
Yellow Honey (approximately 25% mucilage retained): Shorter exposure to sunlight, resulting in fewer enzymatic reactions in the mucilage layer's sugars.
Red Honey (approximately 50% mucilage retained): Slightly longer exposure to sunlight, leading to slightly more enzymatic reactions in the mucilage layer's sugars.
Black Honey (approximately 80% mucilage retained): Longest exposure to sunlight, resulting in the highest level of enzymatic reactions in the mucilage layer's sugars.
Honey processing creates a unique cup profile between natural and washed processing. It offers a cleaner mouthfeel than natural processing and has a richer syrupy sweetness due to the residual mucilage. It also exhibits more pronounced acidity but is more full-bodied than washed processing.
百香蜜處理(Passion Honey Processing)
Passion Honey processing is an evolution of black honey processing. With a higher degree of mucilage retention, the flavor intensity of honey processing is heightened, along with an increased risk of fermentation quality. To go beyond regular honey processing, the Rivas people's processing facility in Costa Rica developed an advanced method called "Passion Honey Processing." It involves drying the cherries with 80% mucilage retention. Unlike black honey processing, the goal is to incorporate more sweetness and fruit flavors from the mucilage into the green beans. This requires an extended drying period of over three weeks to a month, demanding precise control over factors like humidity, temperature, and airflow. On the drying beds, a significant amount of manual labor is involved in daily turning and removing defective beans, while maintaining a lower temperature environment. The resulting honey-processed coffee carries intense tropical fruit characteristics, earning it the name "Passion Honey Processing."
去果皮日曬(Pulped Natural Processing)
Pulped Natural processing is the traditional method of processing green beans in Brazil. The cherries undergo depulping, where the outer skin and part of the mucilage layer are removed, similar to yellow honey processing in the honey process. The coffee beans are then dried in the sun. Pulped natural coffees exhibit a nutty aroma, smooth acidity, and a full-bodied, sweet, and rich taste.
第４大類：厭氧處理法(Anaerobic Fermentation Processing)
Category 4: Anaerobic Fermentation Processing
Anaerobic fermentation processing is an emerging method that imparts a wine-like aroma and distinctive flavor to coffee, elevating the possibilities of flavor development. Inspired by winemaking techniques, this unique processing method involves subjecting whole coffee cherries to anaerobic fermentation before undergoing further processing, such as natural, washed, or honey processing. Therefore, there are variations such as anaerobic natural, anaerobic washed, and anaerobic honey processing.
The processing of coffee beans involves fermentation, which naturally occurs once the cherries are harvested. Fermentation is a natural process that requires two fundamental elements: sugars and water present in the coffee cherries. Fermentation microorganisms can be categorized into aerobic or anaerobic bacteria, which decompose organic matter and alter the coffee's flavor under oxygenated or oxygen-free conditions.
Anaerobic processing allows for more even fermentation and easier monitoring compared to aerobic processing, which is more complex and challenging to control. In an anaerobic environment, the breakdown of mucilage sugars occurs at a slower pace, and the pH decreases at a more gradual rate. This extended fermentation time develops enhanced sweetness and a more balanced flavor profile. Anaerobic fermentation requires a controlled temperature below 10-15 degrees Celsius within a sealed and clean fermentation vessel. The coffee beans ferment in an oxygen-free state for several days, depending on whether they will undergo washed, natural, or honey processing, resulting in various flavor profiles.
Originally a technique used in red wine production, coffee first began utilizing anaerobic fermentation around 2015. Inspired by an Australian winemaker, Sasa Sestic, the World Barista Champion at the time, introduced the method during the competition. Sasa placed ripe coffee cherries in a sealed metal container (stainless steel drum) and injected carbon dioxide while removing oxygen, enabling fermentation and decomposition to occur in an oxygen-free environment. The process allows for effective control over factors such as pH, gas composition, humidity, temperature, as well as the types and quantities of bacteria involved in the fermentation, which develops better sweetness and more balanced taste. This method, known as carbonic maceration, is associated with contemporary grape wines known for their lighter body and intense fruit aroma.
尼加拉瓜Fincas Mierisch的Erwin Mierisch農場自2018年一直在試驗，他發現不僅發酵時間長短具有影響，而且溫度控製也有重大影響。溫度在很大程度上決定所呈現的風味類型，在較熱的發酵中，發現更強烈的味道，如棕色香料(肉桂、丁香、紅糖)；而在較冷的發酵中(在攝氏8-10度發酵)，發現更乾淨和充滿活力的酸度，Mierisch補充說，在Fincas Mierisch，他們更喜歡低溫發酵的結果。
Erwin Mierisch from Fincas Mierisch in Nicaragua has been experimenting with anaerobic fermentation since 2018. He discovered that both the duration of fermentation and temperature control have a significant impact. Temperature largely determines the flavor profile, with hotter fermentations resulting in stronger flavors like brown spices (cinnamon, cloves, brown sugar). In contrast, colder fermentations (around 8-10 degrees Celsius) produce cleaner and more vibrant acidity. Mierisch added that at Fincas Mierisch, they prefer the results of low-temperature fermentation.
Anaerobic fermentation has sparked a small scientific revolution among coffee producers, as they realize they no longer need to rely on luck to improve quality but have more control than ever before. We can all benefit from this advancement, enjoying a more diverse and flavorful coffee experience.
二氧化碳浸漬處理(Carbonic Maceration Processing)
As early as 1872, Louis Pasteur, the father of microbiology, discovered that the flavor of grapes differs when exposed to air compared to a pure carbon dioxide environment. Carbonic maceration processing is also a form of anaerobic fermentation processing. It involves placing whole, unpeeled coffee cherries in a sealed container filled with carbon dioxide gas. In the oxygen-free environment saturated with carbon dioxide, the natural sugars inside the coffee cherries convert into alcohol, carbon dioxide, and various aromatic compounds. The duration of the maceration process can range from several days to weeks, depending on the temperature. The types of microorganisms that can survive and actively participate in fermentation under such conditions are limited to those that thrive in anaerobic environments. The presence of these microorganisms can significantly alter the final flavor of the coffee. The flavors resulting from anaerobic fermentation are often unique, with rich and distinctive aromatic compounds. Currently, different processing facilities and various "carbonic maceration" treatments for green coffee beans vary, so there is no standard or absolute version. The flavors produced are diverse and worth savoring.
The four processing methods mentioned above offer different tasting experiences. Generally, natural processing is associated with sweetness, while washed processing tends to be more acidic. Natural processing brings out fruity notes, while washed processing emphasizes floral aromas. Honey processing offers a balance between the two. Anaerobic processing imparts a distinct and intense flavor profile with a wine-like aroma. Which processing method do you prefer? Consider trying different methods to experience the intriguing sensory journey they offer!
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