Understanding Coffee Roast Levels and Their Flavor Impact

Ever wonder why the same coffee tastes wildly different depending on where you buy it? One shop’s ‘light roast’ might be another’s ‘medium’—or worse, their ‘dark.’ The confusion isn’t just casual—it’s rooted in decades of loosely defined, regional terms like 'Cinnamon' and 'French roast.' How can you know what you’re actually getting? Science, not slang, holds the answer.

The Specialty Coffee Association of America (SCAA) recommends using Agtron numbers—a measurable color scale—to precisely define roast levels. A roast with an Agtron value over 70 is a very light Cinnamon roast; 60–70 is a City (light) roast; around 40 is a Vienna or Full City (medium-dark); and anything below 35 is a dark or French/Italian roast.

What Is a “Roast Level,” Really?

In the U.S., traditional roast terminology includes Cinnamon (very light), City (light), Fully City (medium-dark), and Dark roast (including French and Italian). These terms vary widely by region—what’s ‘light’ on the West Coast might be ‘dark’ back East. Without objective criteria, these labels are inconsistent and subjective.

How Roast Level Is Scientifically Measured: The Agtron Scale

To solve the confusion, the SCAA advocates the Agtron color measurement system, which uses infrared spectroscopy to assess the surface color—and thus the degree of caramelization—of roasted coffee beans. Higher Agtron values mean lighter roasts with less caramelization; lower values indicate darker roasts with more Maillard and caramelization reactions.

The official SCAA Agtron roast classification is as follows:

• Agtron 70 and above: Cinnamon roast (very light)
• Agtron 60–70: City roast (light)
• Agtron around 40: Vienna / Full City roast (medium-dark)
• Agtron below 35: Dark roast, including French and Italian roasts

How Roast Level Affects Coffee Flavor

Roast level dramatically influences a coffee’s flavor profile. In general:

• Acidity: Decreases as roast level darkens. Light roasts preserve more bright, fruity, and acidic notes.
• Coffee Body (mouthfeel): Increases with darker roasts due to more Maillard reactions and bean structure breakdown, leading to a heavier, oilier cup.
• Caffeine Content: Slightly higher in light roasts, as caffeine breaks down at higher temperatures during roasting.
• Sweetness & Roast Flavors: Light roasts highlight origin characteristics like fruit and floral notes, while dark roasts develop deeper tones such as chocolate, nuts, caramel, and smokiness.
• Roast Defects: Poorly executed dark roasts can turn harsh, bitter, and burnt if beans are over-roasted past optimal development.

Light roasts tend to showcase more vibrant, nuanced flavors with higher acidity and a lighter body. They retain delicate floral, fruity, and herbal notes from the coffee’s origin. However, they may lack the roundness or boldness some drinkers prefer.

Dark roasts, on the other hand, develop bolder, richer flavors like dark chocolate, toasted nuts, caramel, and sometimes smoky or spicy notes. The roast itself contributes more to the flavor than the bean’s origin, and body becomes heavier and oilier. But over-roasting leads to bitterness and a loss of complexity.

The Great Roast Debate: Light vs. Dark

The coffee industry remains divided over ideal roast levels, with passionate arguments on both sides.

The Light Roast Camp

Northern Italy, parts of the U.S. East Coast, and roasters like Illy, Green Mountain, and Vivace Espresso advocate for lighter roasts stopped just before or at the start of the coffee bean’s natural oil release—typically around Agtron 40. They argue that coffee oils carry valuable aromatic compounds, and preserving them results in better balance between acidity, sweetness, and body. They claim that letting oils emerge wastes aromatic potential and leads to a less refined cup.

The Dark Roast Camp

Meanwhile, roasters from Southern Italy and the U.S. West Coast—like Peet’s Coffee, Caffe D’arte, and Beans and Machines—insist that coffee must be roasted until it releases oils, typically achieving Agtron values below 35. Some, like Peet’s, go as low as 18 for certain beans. They argue that a dark roast fully develops the bean’s potential, creating a richer, bolder cup with more body, complexity, and the classic roast flavors many drinkers love. They criticize light roasts for being underdeveloped, overly acidic, and lacking depth. Some even suggest that lighter roasts are a cost-saving measure, as only high-quality beans can withstand the intensity of a proper dark roast without turning unpleasantly bitter.

Peet’s, in particular, is respected for expertly managing long, high-temperature roasts—sometimes over 200°C for 15 minutes or more—without producing excessive bitterness. Their ability to coax deep, rich flavors from dark roasts is considered a hallmark of skilled roasting.

Frequently Asked Questions

What is an Agtron number and how is it used in coffee roasting?

An Agtron number measures the color of roasted coffee beans using infrared spectroscopy, indicating the degree of caramelization. Higher values (70+) mean a very light roast; lower values (below 35) indicate a dark roast. It provides an objective way to define roast levels consistently.

Does roast level affect caffeine content in coffee?

Yes. Lighter roasts generally retain slightly more caffeine than darker roasts because some caffeine is lost at higher roasting temperatures. However, the difference is relatively small.

Why do some roasters stop roasting before the coffee beans release oils?

Roasters who favor lighter roasts believe that coffee oils contain aromatic compounds that contribute to acidity, sweetness, and balance. They argue that allowing oils to emerge leads to a loss of these aromas and a less refined flavor profile.

What are the flavor differences between light and dark roast coffee?

Light roasts emphasize origin characteristics like fruit, floral, and acidic notes with a lighter body. Dark roasts develop bolder flavors such as chocolate, nuts, caramel, and smoke, with a heavier body and more pronounced roastiness.

Which roast level is better: light or dark?

There is no universally “better” roast. Light roasts highlight delicate, nuanced flavors; dark roasts offer bold, rich, and robust profiles. Preference is subjective, and both have unique qualities worth exploring.

What roast level is best for espresso?

Espresso can be made with a range of roast levels, but medium to dark roasts (Agtron below 40) are traditional for enhancing body, crema, and the development of roast-driven sweetness. However, light roasts are also used in modern third-wave espresso for more vibrant cups.

Recommended FrontStreet Beans for Roast Exploration

For hands-on roast comparison, try FrontStreet Coffee’s PWN Golden Mandheling (deep roast), known for its low acidity, bold body, and spicy sweetness with notes of herbal depth. The Brazil Queen Manor (medium-dark) offers balanced nuttiness and cocoa with a sweet finish, ideal for seeing how medium-dark roasts enhance body without heavy roastiness. For a brighter contrast, the Colombia Huila (medium) highlights berry and caramel tones, showing how a more moderate roast preserves origin character. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.