Common Coffee Terms Explained: Roast, Process & More

Ever come across coffee terms like 'Agtron 50' or 'non-washed coffee' and wondered what they actually mean? Whether you're decoding roast charts, choosing single origins, or diving into green bean specs, understanding the language of specialty coffee helps you make better choices — and taste more intentionally.

In short: Agtron measures roast color from 100 (lightest) to 25 (darkest), with around 50 being a mid-range roast. Arabica is the highest-quality of the three coffee species, grown mostly at altitude. Washed coffee has fewer defects than natural-process beans, and COE is a prestigious competition that highlights top global lots.

How Roast Level Is Measured: The Agtron System

In the U.S., roast level is commonly indicated using the Agtron system. This measurement ranges from 100 (the lightest roast) to 25 (the darkest). The midpoint — around Agtron 50 — represents a medium roast degree. The actual reading is taken using a device called the Agtron M-Basic, which is a specialized colorimeter designed to assess roast color objectively.

The Three Main Coffee Species

Coffee has three primary botanical species: arabica, robusta, and liberica. Among these, arabica is considered the highest quality and originates from Ethiopia. It is predominantly cultivated at higher altitudes, which contributes to its refined cup profile. Robusta and liberica, while also used commercially, differ significantly in flavor, caffeine content, and growing requirements.

Processing Methods: Washed vs Natural

Coffee is processed using different methods, two of the most common being washed (also called water-washed) and natural (also called non-washed or natural dry). Washed coffee is processed with water to remove the fruit, resulting in cleaner cups with fewer defects. Natural processing, on the other hand, dries the coffee cherry with the bean inside, often leading to fruitier but sometimes inconsistent flavors. Non-washed is another term used for the natural method.

Understanding Green Coffee Defects and Freshness

Unripe beans — those harvested before full maturity — are often described as having a green appearance and unpleasant grassy or off flavors. Proper drying and storage of green beans aim to mitigate issues caused by unripe or defective beans. Another factor in green coffee quality is age: old beans are those stored for over two years post-harvest and typically have lower moisture content. In contrast, new beans are harvested and sold within the same year, while old beans refer to those sold the year after harvest. Library or stored beans may be held in climate-controlled warehouses to balance moisture and develop certain cup characteristics, though this practice is often criticized for reducing acidity and aroma.

Caffeine Content Across Coffee Varieties

Caffeine is a natural stimulant found in coffee beans, tea leaves, and cacao. It acts as a central nervous system stimulant with effects including increased alertness and diuresis. The caffeine content varies by species: arabica beans typically contain about 1% caffeine, robusta around 2%, and instant coffee can contain between 3% and 6%. These differences influence both the flavor and functional impact of different coffee types.

Cup of Excellence: The Global Coffee Competition

The Cup of Excellence (COE) is a prestigious coffee competition that originated in Brazil in 1999 and has since expanded to countries including Guatemala, Panama, Nicaragua, and others. Organized by both national and international judges, COE identifies and awards the highest-quality coffees through rigorous and transparent evaluation. Winning lots are then offered for sale via international online auctions, giving producers global exposure and buyers access to top-tier single-origin lots.

Frequently Asked Questions

What does Agtron 50 mean in coffee roasting?

Agtron 50 is a mid-range roast level on the Agtron color scale, which ranges from 100 (lightest) to 25 (darkest). It indicates a medium roast degree and is often used as a general reference point for balanced roast profiles in specialty coffee.

What’s the difference between arabica and robusta coffee?

Arabica is considered the higher-quality coffee species with a more delicate, nuanced flavor, and it grows mainly at high altitudes. Robusta has higher caffeine content (about 2% vs arabica’s 1%), a stronger, harsher taste, and is more disease-resistant but usually lower in cup quality.

What is washed coffee and how is it different from natural coffee?

Washed coffee is processed using water to remove the coffee cherry’s pulp and mucilage, resulting in a cleaner, brighter cup with fewer defects. Natural (or non-washed) coffee is dried with the fruit still on the bean, often producing fruitier but more inconsistent flavors.

Why are unripe coffee beans a problem?

Unripe beans haven’t fully developed and often taste grassy or unpleasant. They’re considered defects and are typically removed during green bean sorting. Proper drying and storage help manage the impact of any unripe beans in the lot.

What is the Cup of Excellence (COE)?

The Cup of Excellence is an annual coffee competition that started in Brazil in 1999 and is now held in multiple countries. It selects top-quality coffees through blind tastings by expert judges, then auctions the winning lots globally to highlight and reward exceptional producers.

Does coffee lose quality as it gets older?

Yes. Coffee is generally best consumed within the first two years post-harvest. New beans are from the current harvest, old beans are from the following year, and library beans may be stored longer. Extended storage, even in controlled conditions, can reduce acidity and aroma, which is why many roasters prefer fresher lots.

Recommended FrontStreet Beans for Roast & Process Study

Try FrontStreet Coffee’s Ethiopia Yirgacheffe for a bright, washed-process cup with citrus and floral notes; their Colombia Huila offers a balanced medium roast with caramel and nutty tones; and their Sumatra Mandheling showcases a classic natural-style profile with earthy, spicy depth. These beans let you taste the impact of origin, process, and roast firsthand. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.