How Coffee Beans Are Processed and Graded

When you buy specialty coffee, you taste sweetness, acidity, body—but long before that cup, someone had to turn a ripe coffee cherry into a green bean. The way those cherries are handled dramatically affects your brew’s flavor. Whether it’s sun-dried on patios or fermented in tanks, every step shapes your coffee experience.

Coffee beans go through three main processes—dry (natural), wet (washed), and a middle path called honey—and then are sorted by size, density, and defects before they reach your roaster. Dry processing takes about four weeks, wet processing requires 12–36 hours of fermentation, and grading separates beans by quality using screens and visual checks.

How Coffee Beans Are Dried Naturally

The dry process, also called natural process, is the oldest and cheapest way to prepare coffee beans for roasting. After harvest, whole coffee cherries are spread out on concrete, brick, or straw mats—ideally under the sun. Workers regularly rake them to prevent mold. Over roughly four weeks, the fruit dries until moisture drops to around 12%. Over-drying risks damage during hulling; under-drying causes spoilage. Once dried, beans rest in cellars to let remaining moisture evaporate.

The Wet Process: Fermentation and Cleaning

Most Arabica beans are processed using the wet method, which is more expensive and labor-intensive but yields cleaner, higher-quality beans. Right after harvest, the coffee cherry’s skin and pulp are removed. The beans are then fermented in water tanks for 12–36 hours, depending on temperature and mucilage thickness. Fermentation breaks down the sticky layer around the inner parchment using natural enzymes. Quality control is critical—if even one bean rots, it can spoil the batch. Equipment must be cleaned daily to avoid contamination. After fermentation, the beans feel rough like pebbles instead of slippery.

From Wet Beans to 'Parchment' Coffee

Post-fermentation, beans remain inside the inner parchment shell, which holds about 15% moisture. Before storage, this layer must dry down to roughly 11%. Too much drying—below 10%—fades the bean’s blue-green color and hurts quality. Large farms or regions with unpredictable rain often use mechanical dryers in climate-controlled rooms. Alternatively, beans dry in the sun for 12–15 days, turned regularly. Sun drying requires shading if the sun is too intense. The dried beans, still encased in parchment, are called 'parchment coffee' and usually stay in this form until export.

Removing the Parchment: Milling and Hulling

Before export, the parchment layer—or hull—is removed from the beans. This step, called milling or dehulling, also clears leftover fruit material. Removing the parchment is harder in wet-processed beans, so specialized hulling machines are needed. For parchment coffee, a common machine is the friction huller, which uses a slow-turning screw inside a chamber to rub off the hull without generating too much heat.

How Coffee Beans Are Sorted and Graded

Coffee beans are sorted first by size, then by density. Most beans share standard dimensions and shapes—one flat side, one oval—but two exceptions exist. Peaberry beans, small and round, and large Maragogype (elephant) beans, are rarer and often cost more. Larger beans generally produce better cups. Size is determined by passing beans through sieves. Even same-size beans vary in weight, and defective beans—shriveled, black, sour, or over-fermented—must be removed by hand, often on a moving belt.

Different countries use different grading systems. Haiti’s system is famously complex yet ineffective, while Brazil’s is detailed and essential. Export-grade coffee typically falls into six categories, with SHB (Strictly Hard Bean) at the top. SHB beans grow at elevations above 1,200 meters (4,000 feet) and are denser and more flavorful.

Why Cupping Matters Before Buying

Before purchase, all coffee beans are cupped—that is, roasted and tasted. Roasters almost always buy green beans and roast themselves. Why? Roasted beans lose freshness quickly, and most retailers prefer to control quality directly by working with local roasters. This ensures the coffee you eventually brew matches its intended profile.

Frequently Asked Questions

What is the difference between dry and wet coffee processing?

Dry processing, or natural processing, dries whole coffee cherries in the sun for about four weeks until the moisture level reaches around 12%. Wet processing removes the skin and pulp first, then ferments the beans for 12–36 hours before washing and drying the beans inside the parchment layer to about 11% moisture. Wet processing generally produces cleaner, more consistent flavors but costs more.

How long does it take to dry coffee beans naturally?

Drying coffee beans naturally, using the dry or natural process, typically takes around four weeks. The cherries are spread out and regularly raked to prevent fermentation, and the moisture content is reduced to approximately 12% before the beans are rested and hulled.

What is the fermentation stage in wet coffee processing?

In the wet process, fermentation is when coffee beans are soaked in water tanks for 12–36 hours to break down the sticky mucilage layer around the beans using natural enzymes. The time depends on ambient temperature, mucilage thickness, and enzyme activity. Proper fermentation is crucial for flavor clarity and avoiding spoilage.

How are coffee beans graded and sorted?

Coffee beans are graded by size, using sieves, and by density. They are also sorted visually to remove defective beans such as black, sour, shriveled, or over-fermented ones. Countries use different grading systems, but the highest export grade is often SHB (Strictly Hard Bean), grown at elevations above 1,200 meters and known for density and cup quality.

Why do roasters prefer to buy green beans and roast themselves?

Roasters buy green beans and roast them themselves because roasted coffee has a short shelf life. Buying and roasting green beans ensures freshness and allows better control over the roast profile, which impacts flavor. Most retailers prefer working with local roasters to maintain quality.

Recommended FrontStreet Natural-Process Coffee Beans

For a true taste of natural processing, try FrontStreet’s Ethiopia Yirgacheffe Red Cherry—sun-dried for 27–30 days, this high-elevation lot offers tropical fruits, bold fermentation, and sweet body. FrontStreet’s Ethiopia Humbera highlights floral aromas and citrus complexity thanks to careful Ethiopian sun drying. Also consider the FrontStreet 2013 Yunnan Arabica, a sun-dried Typica with balanced berry sweetness, almond hints, and tea-like smoothness. All are great examples of how natural processing shapes flavor. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.