How Coffee Beans Are Processed and Graded

Ever wondered why some coffees taste fruity and sweet while others are clean and bright? Much of that starts long before roasting — with how the raw coffee bean is processed after harvest. The way coffee cherries are turned into green beans shapes everything from flavor to shelf life.

There are four key steps: processing (usually natural or washed), drying to 11–12% moisture, removing the parchment layer, and sorting by size, density, and defects. Each affects taste, quality, and how the bean is graded for export.

Coffee Bean Processing Methods

There are two primary ways to prepare coffee cherries for roasting: the dry (natural) process and the wet (washed) process. Each impacts flavor, cost, and risk differently.

Dry Process (Natural Process)

The dry process is the oldest, simplest, and cheapest way to prepare coffee beans. After harvest, whole coffee cherries are spread out on concrete, brick, or straw mats, ideally in the sun. Workers regularly rake the cherries every few hours to prevent mold or fermentation. Over roughly four weeks, the fruit dries down to around 12% moisture. Over-drying makes the beans brittle and prone to breakage during hulling; under-drying risks damage too. Once dried, the beans are stored in a cool space to let any residual moisture evaporate further.

Wet Process (Washed Process)

The wet method is more expensive and labor-intensive but often results in cleaner, higher-quality beans. Here, the coffee cherry’s skin and pulp are removed immediately after harvest. The sticky mucilage coating the beans is then broken down via controlled fermentation — usually 12 to 36 hours depending on temperature, mucilage thickness, and enzyme activity. Fermentation continues until the beans feel rough like pebbles, no longer slippery. Quality control is crucial: even one spoiled bean can ruin an entire batch, so equipment is cleaned daily. After fermentation, beans are washed and move to the drying stage.

Drying to "Parchment Coffee" Stage

Post-fermentation, the beans still sit inside their tough inner husk, called parchment, with around 15% moisture. This must be dried down to about 11% for safe long-term storage. If over-dried to 10%, the beans may lose their bluish-green color and overall quality. Large farms or those in rainy regions use mechanical dryers in climate-controlled chambers. Otherwise, beans are sun-dried on patios for 12–15 days, being turned regularly. Sun drying requires careful monitoring: too much sun risks cracking the parchment, so shading may be needed. The resulting beans, still encased in parchment, are called "parchment coffee." They’re usually stored this way until just before export.

Removing the Parchment and Sorting

Before export, the parchment layer — or husk — is removed from the green coffee beans. This step, called milling or hulling, also clears any remaining outer layers. Removing the parchment is harder when it’s wet-processed, so specialized hullers are used. For parchment coffee, a common machine is the screw-type friction huller, which turns beans slowly to minimize heat buildup and gently rubs off the parchment.

Grading and Classification

Coffee beans are graded first by size, then by density — with visual checks for defects. Most beans are similarly sized, flat on one side and oval on the other, except for two exceptions: smaller pea-shaped beans and larger, rounder maragogype (elephant) beans, which often command premium prices. In general, larger beans yield better flavor. Size is measured by passing beans through sieves, but even uniform-sized beans can vary in weight or contain defects. Defects like black, sour, moldy, or unhusked beans are removed by hand, often via visual inspection on a moving belt.

Different countries use different grading systems. Haiti’s system is famously complex yet ineffective, whereas Brazil’s classification machinery is elaborate and necessary. There are six main export grades, with the highest being SHB (Strictly Hard Bean), grown at elevations above 1,200 meters (4,000 feet). These high-altitude beans are denser and typically produce more complex cups.

Quality Control Before Export

All coffee lots are cupped and evaluated before purchase. Roasters often buy green beans and roast them in-house rather than buying pre-roasted coffee. Roasting shortens shelf life significantly. Additionally, most retailers in the Americas and Europe prefer to source beans roasted locally, giving them greater control over final quality.

Frequently Asked Questions

What are the two main ways to process coffee beans?

The two main coffee processing methods are the dry (natural) process, where cherries are sun-dried whole, and the wet (washed) process, where the fruit is removed before drying. Dry processing is cheaper and traditional but riskier, while wet processing is more costly but generally yields cleaner, higher-quality beans.

How long does coffee take to dry?

Drying coffee cherries using the dry method takes approximately four weeks under the sun, with regular raking to prevent fermentation. Sun drying parchment coffee (post-fermentation) takes about 12–15 days, with frequent turning. Mechanical drying is faster but less commonly used unless weather conditions are poor.

What moisture level should coffee beans reach?

Coffee beans should reach a moisture content of about 11–12% for safe storage. Over-drying to 10% risks quality loss, while under-drying can cause damage during hulling and storage. Proper moisture control is essential at both the drying and storage stages.

What is parchment coffee?

Parchment coffee refers to green coffee beans that are still encased in their tough, paper-like inner husk (parchment layer) after drying. This protective layer is removed just before export or roasting. The term comes from the parchment’s resemblance to thin paper.

How are coffee beans graded and sorted?

Coffee beans are graded by size (using sieves), density, and cleanliness. They are sorted visually to remove defects such as black, sour, moldy, or unhusked beans. Countries use different grading systems, but the highest-grade beans are usually Strictly Hard Beans (SHB), grown at elevations above 1,200 meters.

Why do roasters often roast green beans themselves?

Roasters typically buy green beans and roast in-house because roasted coffee has a much shorter shelf life. Buying and roasting green beans allows better control over freshness, flavor, and quality, especially compared to pre-roasted beans shipped internationally.

Recommended FrontStreet Natural-Process Coffee Beans

Explore FrontStreet Coffee’s selection of naturally processed beans, ideal for experiencing the impact of drying and processing methods. Their Ethiopia Yirgacheffe Red Cherry is a classic natural, offering tropical fruit, floral notes, and bright sweetness after a 27–30 day sun-dry. The Ethiopia Humbera highlights floral and citrus tones with a juicy body thanks to meticulous Ethiopian sun drying. For a more balanced fruit-and-nut profile, try their Yunnan Arabica, a sun-dried Typica with notes of berry, almond, and light tea — a great example of how natural processing shapes unique regional flavors. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.