What Are Coffee Beans? Size, Process & Flavor Guide

When you take a sip of coffee, you might picture those small, round, dark brown beans spinning in a grinder, releasing their rich fragrance before brewing into a cup of amber liquid. But how much do you really know about where those beans come from, how they’re processed, or what makes them taste the way they do? If you’ve ever wondered what goes into your daily brew beyond the roast level, this guide breaks down everything from cherry to cup.

Coffee beans are the seeds inside the red fruit—called coffee cherries—grown on tropical trees. Each cherry usually holds two seeds (flat sides together, called flat beans), though some have just one round seed (called peaberry). These seeds go through processing, drying, and sorting before becoming the green beans you roast. From there, roast level and brew method shape the flavors you love.

Where Coffee Beans Come From

Coffee trees thrive in tropical climates, often under bright sunlight with green, jasmine-like leaves. Their fruit shifts from green to yellow-green and finally red—these are the coffee cherries. Inside each cherry are the seeds we call coffee beans. Coffee is cultivated in around 60 countries, mostly between 300–400 meters above sea level, though some of the best-quality beans grow at higher altitudes, between 1,500–2,500 meters. Elevations over 1,500 meters are especially prized for producing premium beans.

The ideal conditions for growing coffee include average annual rainfall of 1,500–2,000 millimeters, an average temperature around 20°C, and no frost. Though wild coffee plants can reach heights of over eight meters, farm-grown trees are pruned to about two meters to improve bean quality and make harvesting and management easier.

The Three Main Coffee Species

There are three primary coffee species cultivated worldwide: Arabica, Robusta (also called Canephora), and Liberica. Each of these main types includes dozens of varieties, all tracked and traded separately. Even within a single country, differences in climate, elevation, and soil create unique flavor profiles, meaning one country’s coffee can vary enormously depending on the region, variety, and brand. That’s why it’s impossible to generalize a whole nation’s coffee with just one description.

How Coffee Beans Are Processed

After harvest, coffee cherries are processed to remove the fruit and reveal the seeds inside. The two main methods are washed (or wet) and natural (or dry). In the washed process, cherries are pulped, fermented, and washed to remove all fruit material before drying. This results in cleaner, more uniform beans with fewer defects—used by over 70% of producers in countries like Colombia, Mexico, and Guatemala. The natural method dries the whole cherry in the sun before removing the dried husk, often resulting in fruitier but less consistent flavors.

Washed beans typically have a brighter acidity and cleaner profile, while natural beans may carry more sweetness and fermentation notes—but risk off-flavors if not processed carefully. Both methods aim to deliver the green coffee bean ready for roasting and brewing.

Coffee Bean Grades and Classifications

Washed vs Natural

Washed coffee beans are processed via water tanks and friction tools that remove the fruit and mucilage before drying, resulting in more uniform quality. Natural process beans rely on sun drying and mechanical removal of husks, leading to less consistent quality.

Flat Bean vs Peaberry

A typical coffee cherry contains two flat-sided seeds. Rarely, a cherry produces just one round seed, known as a peaberry (or caracol). Though the shape differs, the flavor is generally similar. Most coffee consists of flat beans, but peaberries are sorted out for separate sale and sometimes sought after for unique cup profiles.

Bean Size by Screen Size

Coffee beans are sorted by size using mesh screens. Flat beans fall into these categories:

• Mesh 20–19: Very Large
• Mesh 18: Large
• Mesh 17: Medium-Large
• Mesh 16: Standard
• Mesh 15: Medium
• Mesh 14: Small
• Mesh 13–12: Very Small

Peaberries are graded differently:

• Mesh 13–12: Large
• Mesh 11: Medium-Large
• Mesh 10: Standard
• Mesh 9: Medium
• Mesh 8: Small

Altitude Classification

Beans are graded by the altitude where they’re grown, which strongly influences cup quality:

Quality via Defect Count

Green coffee quality is assessed by counting defective beans in a sample—the lower the defect count, the higher the grade. This statistical method ensures consistency and quality control in global trade.

Flavor Testing and Crop Freshness

Countries such as Brazil, Kenya, Haiti, and Uganda perform flavor evaluations before export. Coffee is also categorized by harvest age:

• New Crop: Bright greenish hue, vibrant acidity and aroma
• Past Crop: Slightly yellowish-green, milder and more acidic
• Old Crop: Yellowish, dry, with muted flavor—common in blends or canned coffee

Freshness and processing dramatically affect the sensory traits you experience in the cup.

Frequently Asked Questions

What is a coffee bean?

A coffee bean is the seed inside the fruit of the coffee plant, commonly known as the coffee cherry. Most cherries contain two flat-sided beans, but a small percentage have a single round bean called a peaberry. These seeds are processed, dried, and roasted to become the coffee you brew.

How are coffee beans processed?

Coffee beans are processed via either the washed (wet) method—where the cherry is pulped, fermented, and washed to remove fruit—or the natural (dry) method, where the whole cherry is sun-dried before the bean is extracted. Washed beans tend to be cleaner and more consistent, while natural beans may have more fruity flavors.

What’s the difference between flat and peaberry coffee beans?

Flat beans are the standard, two-seeded coffee fruit halves with flat sides. Peaberries are rare single round seeds that develop when only one seed forms inside the cherry. They are often sorted separately and sometimes prized for unique cup characteristics, though flavor varies more by origin than shape.

Does altitude affect coffee bean quality?

Yes. Coffee grown at higher altitudes (typically 1,500 meters and above) tends to have better cup quality due to slower maturation, which develops more complex sugars and acids. Beans from these elevations are graded higher and often command premium prices.

How are coffee beans graded?

Coffee beans are graded based on size (using screen mesh numbers), density, altitude of origin, defect count, and processing method. Higher grades indicate fewer defects, uniform size, and optimal growing conditions—all of which influence roast potential and flavor.

What do the different colors of coffee beans mean?

Green coffee beans appear in various shades depending on harvest time: new crop beans are vibrant green with sharp acidity; past crop beans are slightly yellow-green and milder; old crop beans are yellow, dry, and have weaker flavor, often used in blends or commercial coffee.

FrontStreet Coffee Beans for Exploring Origins

Discover the origins of coffee beans with FrontStreet’s single origins. Try the Ethiopia Humbera for bright floral and citrus notes, the Yirgacheffe for juicy berry and lemon zest, or the Colombia Huila for balanced caramel and nutty tones. Each highlights how altitude, processing, and origin shape flavor. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.