Identifying Roast Levels

The journey coffee takes from a green, grassy seed to the aromatic brown bean we grind and brew is a complex process of chemistry and physics. For the consumer, understanding roast levels is not merely about colour preference; it is about predicting flavour, acidity, and body of freshly roasted coffee beans.

The speciality coffee industry generally categorises roasts into four distinct phases: Light, Medium, Medium-Dark, and Dark. However, identifying these levels accurately requires looking beyond the shade of brown to observe surface texture, oil presence, and specific sensory characteristics.

The Science of the "Crack"

To understand roast levels, one must first understand the "crack". As coffee beans are heated, the water inside them turns to steam. Pressure builds until the bean expands and cracks open audibly, similar to popcorn.

• First Crack: Occurs around 196°C. This marks the point where the bean is officially roasted and edible.

• Second Crack: Occurs around 224°C. This indicates the breakdown of the cellulose structure of the bean, releasing oils to the surface.

Roasters use these audible cues, alongside temperature probes and colour analysis (often measured by an Agtron scale), to determine exactly when to drop the beans into the cooling tray.

Light Roast: The Taste of Origin

Internal Temperature: 196°C – 205°C
Common Names: Cinnamon, Light City, Half City, New England.

Light roasts are stopped just after the first crack. Visually, these beans are a pale, matte brown with absolutely no oil on the surface. Because they have not been subjected to extreme heat for long periods, they retain the most chemical characteristics of the original green coffee bean.

In the cup, light roasts are defined by high acidity, often described as "brightness". This is where you taste the terroir of the coffee: the soil, altitude, and processing method. You might detect floral notes, citrus fruits, or stone fruits. Contrary to popular belief, light roasts often retain slightly more caffeine by volume than darker roasts, though the difference is negligible by weight.

Medium Roast: The Balanced Cup

Internal Temperature: 210°C – 219°C
Common Names: City, American, Breakfast.

Medium roasts are perhaps the most ubiquitous in the Western world. These beans are dropped between the end of the first crack and just before the beginning of the second crack. They appear a slightly richer brown than light roasts but generally remain non-oily.

At this stage, the Maillard reaction (the chemical browning process that creates flavour) has developed sugar browning notes. The intense acidity of the light roast is muted, replaced by a balance of flavour, aroma, and acidity. The body of the coffee becomes fuller. This is often considered the standard "coffee" taste, neither too acidic nor too bitter.

Medium-Dark Roast: The Turning Point

Internal Temperature: 225°C – 230°C
Common Names: Full City, Vienna.

This roast level marks the beginning of the second crack. Visually, the beans become a deep, rich brown, and you will begin to see patches of oil, a sheen caused by internal lipids migrating to the surface.

Flavour-wise, the characteristics of the roast begin to overshadow the characteristics of the bean. The bright acidity is almost entirely gone, replaced by a heavy body and spicy or bittersweet notes. You may taste caramel, dark chocolate, or toasted nuts. This is often the preferred roast for traditional espresso blends, as the lower acidity pairs well with milk.

Dark Roast: The Taste of the Roast

Internal Temperature: 240°C – 245°C
Common Names: French, Italian, Spanish, Continental.

Dark roast beans are shiny and coated in oil. They range from dark chocolate brown to nearly black. At this stage, the sugars within the coffee have begun to carbonise.

The dominant flavours here are smoky, ash, tar, and burnt sugar. The origin character of the bean is effectively erased; a high-quality Ethiopian Geisha roasted this dark will taste virtually identical to a standard Brazilian bean roasted to the same level. The mouthfeel is thin, and the aftertaste can be bitter. While often marketed as "strong", this refers to the bitterness of the roast, not the caffeine content, which is slightly lower per bean due to the loss of mass during the extended roasting process.

A Glance at Roast Characteristics

The following table provides a quick reference guide to identifying roast levels based on visual and sensory data.

Freshness and Roast Levels

It is important to note that roast level affects the shelf life of fresh coffee. The roasting process causes coffee beans to release carbon dioxide (degassing). Darker roasts, having a more porous structure due to the second crack, degas much faster than light roasts. 

Furthermore, the oils present on the surface of dark roasts oxidize rapidly when exposed to air, leading to rancid flavours. Therefore, while a light roast might maintain peak freshness for three to four weeks, a dark roast is best consumed within two weeks of the roast date.

The Role of Quality Beans

Understanding the science of roasting levels empowers you to choose a coffee that suits your palate, but even the most precise roast profile cannot fix poor-quality green beans. The foundation of an exceptional cup lies in the raw material.

This is where The Blind Coffee Hero steps in. Whether you are brewing a morning cup at home or managing a bustling coffee shop, the integrity of your ingredients is paramount. 

The Blind Coffee Hero provides freshly roasted coffee beans that honour the hard work of the farmers and the science of the roast. By sourcing high-quality beans and ensuring they are roasted to perfection and delivered fresh, we ensure you extract the very best potential from every single bean. For the ultimate coffee experience, always prioritise freshness and quality in your cup.

Subscribe to The Blind Coffee Roaster today.