Roasting 101: The Phases of Coffee Roasting

Welcome to Royal New York’s Roasting 101! In this guide, we’re diving into the three fundamental phases of coffee roasting. Whether you’re an aspiring home roaster or a specialty coffee roasting expert, understanding these phases—drying, caramelization, and development—is essential for anyone passionate about perfecting their roast. Elevate your coffee game with Lab Coordinator and coffee roasting expert Mike Romagnino as he breaks down the phases of coffee roasting for you below!

Green coffee being roasted in a Loring coffee roaster at the Royal New York Lab showcasing one of the coffee roasting phases

Coffee Roasting Phases

#1: The Drying Phase

Did you know that specialty green coffee is imported with 10-12% moisture still left in the bean? In fact, the moisture level is key to maintaining quality. That being said, the beans require a final drying phase before roasting.

First, the drying phase begins when the coffee is charged into the drum at the start of the roasting process. Once inside the drum, the coffee absorbs heat, causing the remaining moisture to turn into steam. As a result, both mass and density are reduced. Depending on your roasting approach, style, and/or equipment, this drying phase typically lasts between 4–7 minutes. It’s imperative to pay attention to how long you are in the drying phase. If you rush this phase, you may have uneven heat distribution and external burning. However, prolonging the drying phase can result in underdeveloped roasting.

The heat applied during the drying phase sets the tone for the entire roast and influences the subsequent phases. When the coffee finishes turning from green to yellow, you have arrived at color change, leading to the next coffee roasting phase: caramelization.

#2: The Caramelization Phase

The caramelization phase is the time between yellowing and first crack. It’s during this phase that sugars within the bean undergo breakdown, or caramelization, due to their exposure to high temperatures inside the drum. Controlling the length of this phase, as well as the rate at which it occurs, is crucial to effective roasting. This is an opportunity to maximize flavor development from the chemical reactions that are occurring.

Overall, the most important reaction of the caramelization phase is the maillard reaction. The maillard reaction is a non-enzymatic browning caused by the interaction of simple sugars and amino acids. Furthermore, non-enzymatic browning is a chemical process that produces a brown color in foods without the activity of the enzymes. When this interaction breaks apart these simple sugars and amino acids, it forms a wide range of new flavors and aromatic compounds. In turn, the amount of heat you apply and rate of duration through the maillard reaction will have a significant effect on your roast.

#3: The Development Phase

As soon as first crack occurs, you have entered the final phase of the roasting process: development. First crack can be defined as an exothermic reaction that releases built up energy, steam, and carbon dioxide. In coffee roasting, first crack is the result of the water inside the bean transforming into steam. When the moisture creates steam, it builds up pressure, causing the beans to crack open.

Development is a crucial phase as it allows the roaster to control and develop the flavor profile of the coffee. During this phase, the roaster monitors the coffee while it undergoes the aforementioned chemical reactions that transform the flavor. The sugar and acids within the beans begin to caramelize, contributing to the development of complex flavors and aromas. By carefully managing factors such as temperature, airflow, and duration during this phase, the roaster can highlight specific flavor characteristics and achieve the desired balance between acidity, sweetness, and body in the final cup.

Final Thoughts on Roasting Phases

The coffee roasting phases serve as the foundation upon which consistency and quality are built in every batch of roasted coffee. As you embark on your coffee roasting journey, remember to keep the nuances of the drying, caramelization, and development phases top of mind. Happy roasting!

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