Coffee Roasting Explained

November 09, 2022

Achieving the browned, flavorful roasts that we purchase at the grocery store requires a great deal of craftsmanship. Coffee roasters are tasked to find a delicate balance between heat and time to attain desired results. In many ways, coffee roasting comes down to a science, but some might view it as a true art form.

Each coffee bean variety comes with its own recipe for achieving desired roasts. These formulas factor in qualities like a bean’s size, moisture content, and flavor profile that evolve once coffee comes into contact with heat. By placing immense attention to detail from start to finish, coffee roasters can create some remarkable brews.

The Purpose of Coffee Roasting

Green coffee beans, as is, are a very different ingredient from their final roast. Before they enter the roaster, the beans are just dried seeds that lack the flavors you taste in your coffee, or at least until heat brings those flavors out.

Check Roast Dates

Roasted coffee beans slowly lose their flavor and aroma over time and are usually at peak quality within a few days of their original roast dates. Check your coffee’s packaging for its roast date and aim to buy in small batches to get the most out of your beans.

The Three Stages

Heat completely transforms green coffee, both physically and chemically. The roasting process is divided into three stages: drying, browning, and development.

The initial drying phase lowers the coffee bean’s moisture content, which is necessary prior to roasting. The time and temperatures involved in this stage depend on the specific roasting vessel being used, but roasters act carefully to not accidentally burn the coffee.

Once the beans’ moisture is lowered to optimal levels, it’s time for the roasting process to begin. This “browning phase” takes up the majority of the roasting process, consisting of 80% of the entire operation. It’s in this phase that all of the chemical processes take place, and the beans experience transformations in color, aroma, flavor, and density.

The Maillard reaction that takes place jumpstarts the browning process, lowers the coffee’s natural sugar content, and sparks reactions between amino acids to create coffee’s aroma and flavor. Towards the end of the browning process, roasters hear an audible “crack,” which signals that the development phase has begun.

Coffee beans’ development phase entails the entire process slowing down to provoke an exothermic reaction. The energy inside the beans is released, causing the roasted seeds to explode, further crack, and form their aromatic characteristics. The cracks signal to the roaster where the batch is in the roasting process, with roast degrees falling on a spectrum between light and dark roasts.

Roast Spectrum

The longer raw coffee beans are exposed to heat, the longer the list of chemical transformations they experience. Overexposure to heat creates burnt and bitter coffee, but carefully handling roasts allows roasters to balance acidic, bitter, sweet, and astringent flavors.


Since light roasts are roasted for less time than darker batches, the beans maintain much of their natural fruitiness, sweetness, and floral notes. This makes light roasts more complex in flavor with a crisp acidity, meanwhile having less “body” than darker roasts.

Light roasts reach temperatures between 350-410ºF in the roaster and lack the oily shine seen in dark roasts. Caffeine content also diminishes throughout the roasting process, meaning that lighter roasts have higher levels of caffeine per serving.


Medium roasts reach temperatures between 410-440ºF in the roaster. These roasts have a less acidic, more balanced flavor and more body than light roasts. Traces of the coffee beans’ sugar contents are still present in medium roasts’ profiles.

At this time, all of Lardera's roasted offerings are between light and medium roasts.


Dark roasts reach temperatures over 440ºF to form a full-bodied cup with lower amounts of caffeine and natural acidity. These beans are also known for the signature smoky, earthy flavor with hints of chocolate, nuts, and spices. More prolonged exposure to heat draws out coffee’s natural oils as well, forming a glossy, almost blackened surface on the beans.


Medium-Dark roasts exist in between Dark and Medium in both flavor and appearance. These beans are less acidic and floral in flavor than light roasts, yet have more body, similar to dark roasts. Medium-Dark beans are also darkened in appearance with an oily exterior but not as blackened or shiny as Dark roasts.