Coffee processing methods of the world’s top coffees is achieved by many different methods. These processing techniques can be grouped into four categories: Wet Processing (Washed), Dry Processing (Natural, Sun Dried), Pulped Natural Processing, and Semi-Washed Processing.
Farmers choose the processing method best suited for their climate and capabilities – whether they have a long, dry season to allow for dry processing, or ample water supply because of a high tropical environmental, and how much labor they have access to.
Here’s a quick guide of all of these coffee processing methods, with detailed explanations:.
- Wet Processing involves washing the coffee beans of fruity material while the beans are still moist right after they are picked.
- Dry Processing involves first drying the coffee cherry in the sun while regularly raking the beans free of any dried fruit.
- Pulped Natural Processing involves initially pulping the coffee but without a fermentation stage as in Wet Processing, then drying the beans with much of the mucilage still attached.
- Semi-Washed Processing method a demucilaging machine is used to remove the coffee cherry’s skin and most of the mucilage.
- Aquapulp is another method which cleans the coffee cherry initially and has recently been adopted by many areas that formerly used wet processing.
Once the coffee beans are processed they are usually bagged in 100-pound, 132-pound or 154-pound coffee sacks and sold on the world market as green coffee beans (milled, but not yet roasted).
The wet processing method (washed) involves soaking the coffee cherries and allowing fermentation to take place to separate the cherry from the bean – or it can be run through a mechanical depulper to remove the coffee cherries. Once the green coffees are removed, they’re washed once again to remove residue and placed outside to dry on a patio or raised beds.
The flavor of the resulting coffee is more “pure” than other methods – unaffected by the coffee cherry.
Coffee suppliers use different types of coffee processing methods, as well as the flavor and fragrance required for the final product, depending on where coffee is produced.
Coffee processing is a critical step in making coffee for those who don’t know where coffee fruits are converted into the ultimate commodity-coffee beans.
It is simply impossible to use the dry processing system for countries with heavy rain and high air humidity. So coffee farmers from India, Indonesia and Vietnam have opted to use different methods called wet processing.
Because the wet processing method is quite invasive compared to dry processing, it is only used from Arabica beans for coffee forms. Robusta coffee beans are not processed with this system because of their low quality, low final price and consequently low profit.
The main characteristic of the wet process is that the pulp and all the skins in the coffee fruit are discarded before drying the beans.
This is a fully automated approach that requires many steps:
- Clean and sort coffee berries, scrape all soil, leaves, overripe berries, etc.
- Coffee beans pass through several machines that were used in the second step to remove pulp and flesh from the coffee bean.
- Coffee beans are going to a large water tank filled with natural enzymes for the next 24-36 hours. During this time, enzymes eliminate everything that has not been removed during the washing and pulping cycle (this is the fermentation process).
- During fermentation, coffee beans are washed with clean water and sent for cooling. The drying process is finished when the coffee moisture level at the beginning of the drying process is 12.5 percent instead of 60 percent.
- Unlike the first stage of cleaning, after one last wash, this method is used to clean coffee bean only in the event that there are any leftovers and processing. Also known as hulling, this stage is the word used in the dry process.
Wet coffee flavor system and fragrance
Using wet method, coffee beans usually produced have a cleaner color and appearance. Of course, flavor and aroma is the most important part of every coffee bean. The smoother, healthier and clearer taste of the wet coffee cycle (also known as light coffee). It has an enticing fruity aroma. For these reasons, many people love this coffee more than dry process coffee, which has a more earthy taste.
Dry processing is a type of coffee processing that involves drying the freshly picked coffee cherry (fruit) in the sun for a period of time on large patios while repeatedly raking and turning the drying cherry until the green coffee beans are generally free of any dried fruit and the humidity content is about 10.5 percent. Instead of sun-drying, automatic dryers can be used.
Then either the dried fruit is disposed of as waste, or if there are services, it can now be refined into a coffee flour.
Through this method, while the coffees acquire unique flavors, it’s also a risky bet–it takes at least 2 weeks without sun to allow for drying. Rain or high humidity contributes to mold and fungus growth and can kill a crop–sometimes the entire income of a farmer.
Dry processed coffees tend not to have a vast array of flavors, as the coffee cherry always pushes the flavor toward fruity and sweet. Dry processing is particularly important for Brazilian, Ethiopian and Yemenian coffees.
Another key consideration is the amount of water required–dry processed coffees can use as little as one gallon per kilogram of dried parchment, whereas wet processing takes more than 10 gallons per kilogram of dried parchment.
Coffee parchment (pergamino; pergaminho) is the resulting product. The residual fruit remains on the dry processed coffee add more body to the brewed coffee beverage, while wet processed (washed) coffees appear to have a more desirable acidity level.
Coffee Drying – Divisadero Coffees
A benefit of the dry processing method is that because of the fruit remains left in with the coffee beans, the brewed coffee tends to have more body than wet-processed coffee.
Most coffee experts think that wet-processed coffees are superior to non unwashed (dry-processed; natural) coffee, but this is simply a matter of personal preference.
Sometimes known as “pulped natural”, “semi washed”, “dry milled” or “honey coffee”.
Pulped natural / semi dry / honey process
The pulped natural or “semi-dry” process involves extracting various portions of the coffee cherry– between Wet Processing and Dry Processing. Recently, these varying amounts have become known respectively as “black honey,” “red honey” and “yellow honey”–more of the coffee cherry left on the outside results in more caramelizing and darker color. Less coffee cherry, on the other hand, means less sugar and a light hue.
What is “Pulped Natural” Coffee Processing?
Pulped Natural processing is a procedure that removes the coffee cherry’s outer skin to reveal the fruity layer and then helps it to dry in the sun (or with mechanical dryers sometimes). Between dry processing and wet processing, it is called halfway–taking more processing time and consuming more water than pure natural processing, but also providing a better quality cup.
Pulping the Coffee to Remove the Outer Skin
The pulped natural processing method often used in Brazil, where strip-picking is the norm, involves first pulping the coffee to remove the outer skin, although this is done without fermentation. The coffee cherry is then sun-dried on a raised drying bed or on a patio, with much of the mucilage still attached.
The pulped coffee cherry can also be ground into a fine powder known as coffee flour, as well as having a high nutritional content with plenty of potassium and fiber and natural caffeine.
Regions Where Pulped Natural Processing is Used
The processing method of pulped natural coffee works best in regions where humidity is low so that the mucilage of the coffee can be easily dried without fermentation. To prevent mildew, coffees need to be turned periodically, which can lead to mold and fungus.
Characteristics of Coffee with Pulped Natural Processing
The pulped natural method exhibits features of both wet processing method (good acidity) coffee and dry processed green coffees (sweetness, body), with some of the full flavor of dry processed coffee in the cup, comparable to a wet processed coffee.
Pulped Natural processing is done to bring out the coffee’s natural sweetness and aromatics–if done properly, it will result in a better coffee taste.
Wet hulled / Semi washed
Coffees are pulped at the farm using this method to strip the coffees down to parchment and mucilage, then sent to the processing facility for processing. In Indonesian countries, this is also known as “Giling Basah” (wet grinding).
Usually, the processing technique is passed down within a country through generations, with current farmers doing something very close to what their fathers and grandfathers did, and so on. Sometimes government organizations and international coffee organizations step in to provide alternative methods or share their techniques, which helps raise industry-wide standards.
However, some methods are simply unavailable or too expensive–the processors may be limited in their options in areas where water is scarce or equipment is unavailable. While it’s hard to imagine in countries like Canada, the United States, the United Kingdom, and Australia in the first world, much of the coffee-growing world is constrained by lack of knowledge and the lack of basic equipment.
What is “Semi-Washed” Coffee Processing?
Demucilaging in the Semi-Washed Processing Method
The semi-washed coffee processing method involves using a demucilage machine to strip the coffee cherry skin from the green coffee itself as well as some or most of the mucilage.
Characteristics of Coffee with Semi-Washed Processing
Coffee beans processed using the semi-washed method are somewhat similar to coffee processed using the natural pulped method and similar to wet processed coffee, displaying a bright, clean cup with a little less body than dry processed coffee.
Pulping typically takes place within 24 hours after the coffee cherry (fruit) is harvested and involves removing the outer flesh of the coffee cherry (red skin and mucilaginous pulp). Typically this is achieved with a machine known as a pulper that loosens and splits the outer part of the cherry using rough rollers.
Demucilaging, drying, and hulling
Next the mucilage of the coffee cherry is removed by fermentation by placing the cherry for 12 to 24 hours in a fermentation tank.
Then the coffee beans are dried either by forced-air drying or spread over decks or patios (see hoshidana) to dry naturally in the sunlight (see sun-drying). After drying, coffee beans usually have a moisture content of about 10.5 percent.
Hulling / husking is performed with a machine called a huller that mills off the parchment and the silver skin and also polishes the beans that are known as green coffee beans at this point (milled but not yet roasted).
Aquapulp coffee processing
Aquapulp is the process of removing the sticky pulp or mucilage of the freshly-picked coffee cherry, by means of mechanical demucilage, using machines to clean the cherry.
Gradually, the aquapulp process replaced conventional wet processing methods for extracting mucilage through fermentation and washing.
The coffee beans are sorted and graded based on local standards that vary in different regions after the parchment is removed. The beans are generally sorted into grades of quality based on size, shape, and other factors. (See also Coffee Beans Grading.)
Graduated hole sizing screens assist in completing the grading process. Also used are vibrating air tables, using gravity to divide the beans by density and to isolate damaged (e.g., hollow or nicked) coffee beans that can affect the final product’s taste.
Criteria Used for Grading Coffee Beans
The grading of coffee beans is a rating of quality based on certain requirements.
The grading criteria may include coffee bean size, coffee bean hardness (e.g., density), rising altitude, color, fragrance, number of bean imperfections or defects (e.g., hollow, deformed, chipped, nicked, etc.), coffee bean type / plant type purity (e.g., botanical variety, variety), number of underripe beans and/or overripe beans, method of processing used to remove beans from coffee cheese.
Coffee Grading Methods by Region
Every area that grows coffee has its own method of grading coffee beans. It allows a country or region to take coffees from any number of farms–often hundreds or thousands–and to produce a consistent product in other countries for coffee importers and brokers.
Screens with Graduated Hole Sizing
Use screens with graduated hole sizing, coffee beans are often divided into quality groups–this divides the beans by size and shape.
A vibrating air table that uses gravity to separate and grade the beans by density is also used to grade the beans. This also isolates the defective coffee beans that may be nicknamed, hollow, or other imperfections, and if these coffee beans are not removed, the overall quality of the coffee may be reduced.
Electronic and Mechanical Coffee Bean Grading
Electronic and mechanical grading–by scale, weight, shape and color–occurs after the Kenya coffee beans are milled and the best coffee beans are extracted while any faulty beans are removed which may add off-taste to a coffee.
Clearing Extraneous Materials
If coffee beans were not cleaned of foreign materials during processing and sorting (e.g. removing all foreign matter such as pebbles, wood, insects, etc.), this may also affect coffee beans grading. It is not uncommon to receive bulk bags of green coffee beans with foreign fragments, mostly benign and destroyed during the roasting process, even with proper processing.
Other Coffee Grading Systems
Many countries use other coffee bean grading methods. With the introduction of new technology and machinery, the grading and processing of coffee beans has shown continuous improvement in coffee growing regions around the world. For Sorting as well.
Many coffee processors that sell whole green coffee beans leave the silverskin on the bean as it acts as a protective barrier and then crumbles naturally during the process of coffee roasting. The silverskin is polished by other coffee processors.
The final step in preparing coffee for consumption is roasting, which involves heating / cooking / drying coffee beans in a coffee roaster to alter the green coffee beans ‘ physical and chemical properties in order to achieve the desired flavors and aromas of the final cup of brewed coffee.
Coffee roasting removes most of the coffee beans ‘ moisture and starts a sequence of chemical reactions called pyrolisis. Such chemical reactions modify the coffee beans’ chemical composition and produce the coffee compounds associated with the brewed coffee’s flavors and aromas.
The professional roastmaster’s aim is to apply the perfect roasting temperature for just the right amount of time to deliver the best flavors of the individual roasted coffee beans.
Roastmasters pay close attention to roasting coffee beans’ color level as they grow and change their hue. The roasting coffee beans ‘ color varies from very light to very dark, and their density often changes as coffee beans lose moisture.
Coffee roasting produces, modifies and/or stabilizes the coffee beans ‘ scent as well as the body, flavor, sweetness / bitterness, acidity and aroma of the brewed coffee in different aspects and instances.
Coffee roasting machines
As well as a proper coffee roaster, roasting coffee requires skill. Most that roasting machines are heated using propane gas to drive a drum using electricity. Temperatures range from 370 ° Fahrenheit to 540 ° Fahrenheit (188 ° Celsius to 282 ° Celsius).
Roasting times vary from about 12 to 30 minutes, and the beans shrink by weight by about 20 percent as they develop a dark flavor and aroma. Usually, 25 of the green coffee beans take about 15 minutes to roast, and 8 pounds of coffee cherry is about 1 pound of roasted coffee (100 pounds of coffee cherry is about 12 pounds of roasted coffee).
Fluid bed roasters
A Fluid Bed Roaster is a type of coffee roaster that uses a column of hot air to agitate and roast the green coffee beans. After Michael Sivetz who invented it, the Fluid Bed Roaster, sometimes called a Sivetz Roaster, works much the same as a popcorn popper.
Total roasting time for coffee varies depending on several factors including coffee bean quality, moisture content, and coffee bean grade. The age of the coffee beans and the weather conditions in which the coffee roasting is done are also affecting the roasting time.
The type of roast required, ranging from Light Roast to Medium Roast to Semi-Dark Roast to Dark Roast, is a primary factor in determining coffee roasting time.
The skilled roastmaster pays attention to the roasting time and temperature as well as more subtle considerations such as the coffee beans ‘ appearance and fragrance during roasting.
The roastmaster listens to the roasting coffee beans ‘popping or cracking noises–these distinct “cracks” occur during roasting at specific times.
Once the coffee beans are roasted they are ready for grinding and then brewing.
There you go, you now know the different types of coffee processing methods. learning about coffee farming and how its being processed while taking a sip of your favorite coffee type drink is a wonderful way to appreciate it every day.