Roast Profiles Explained: Light, Medium, Dark

Roasting is where green coffee becomes the brown, aromatic product you grind and brew. It is a thermal process that triggers hundreds of chemical reactions, and the degree to which those reactions progress determines what ends up in your cup. Light, medium, and dark are not just colour labels. They represent fundamentally different flavour profiles driven by different chemistry.

What Happens During Roasting

Green coffee enters the roaster at room temperature and absorbs heat. The first phase is endothermic: the bean is absorbing energy, drying out, and turning from green to yellow. This takes about 4 to 6 minutes in a typical drum roaster at a charge temperature of 200 degrees Celsius.

Around 150 to 170 degrees Celsius internal bean temperature, the Maillard reaction kicks in. This is the same reaction that browns bread, sears steak, and gives caramel its flavour. Amino acids and reducing sugars combine to form hundreds of new aromatic and flavour compounds. The bean turns from yellow to tan to light brown. This phase produces sweetness, body, and complexity.

At around 196 degrees Celsius internal temperature, first crack occurs. Steam and CO2 that built up inside the bean during the Maillard phase force the cellular structure to fracture. You hear an audible popping sound, similar to popcorn. First crack marks the beginning of drinkable coffee.

Light Roast

A light roast is stopped shortly after first crack, typically at an internal temperature of 196 to 205 degrees Celsius. The bean is light brown with no oil on the surface.

Flavour profile: high acidity, light body, origin character dominant. You taste the terroir: the soil, the altitude, the variety. Floral, fruity, and tea-like notes are most prominent. Sweetness is present but delicate.

Light roasts are the best way to taste what makes a specific coffee unique. They are also the least forgiving when brewed. Under-extraction produces sour, grassy flavours. Over-extraction produces astringency. Dial in your brew carefully.

Medium Roast

A medium roast continues past first crack into the development phase, stopping at around 210 to 220 degrees Celsius. The bean is medium brown, still no surface oil.

Flavour profile: balanced acidity and body, sweetness at its peak. Caramel, chocolate, and nutty notes from the Maillard reaction are now prominent alongside the origin character. This is where most specialty coffee roasters operate because it balances origin flavour with roast-developed sweetness.

Medium roasts are the most versatile. They work well across brewing methods, from espresso to pour-over to French press. If you are new to specialty coffee, start here.

Dark Roast

A dark roast pushes into or past second crack, at internal temperatures above 225 degrees Celsius. The bean is dark brown to nearly black, with visible oil on the surface. The cellular structure has fractured further, and the bean is more porous and brittle.

Flavour profile: low acidity, heavy body, roast character dominant. Smoke, dark chocolate, charcoal, and bittersweet notes. Origin character is largely obscured by the roasting process. A dark-roasted Ethiopian and a dark-roasted Colombian will taste more similar than different.

Dark roasts are not inferior. They are simply different. Some people prefer the boldness and the absence of bright acidity. French press and cold brew handle dark roasts particularly well. But if you are paying a premium for single-origin specialty coffee, a dark roast will mask the very qualities you are paying for.

Development Time

There is a concept in specialty roasting called development time ratio (DTR): the percentage of total roast time that occurs after first crack. A DTR of 15 to 20% is typical for a medium roast. Below 12% and the coffee will taste grassy and underdeveloped, even if the colour looks right. Above 25% and roast flavours begin to dominate.

This is why colour alone is an unreliable indicator. Two coffees can be the same shade of brown but taste completely different because one had adequate development time and the other did not. Trust your roaster's palate more than the colour of the bean.