The Art of coffee roasting

The roasting process magically transforms raw green coffee beans into aromatic delights, turning us into devoted coffee enthusiasts. As we mentioned before, the key player in roasting is the roaster itself, but without a skilled roast master, even the most advanced equipment is just an expensive metal box.

The role of a roast master

A true roast master is a connoisseur of coffee descriptors, possessing an incredibly refined palate capable of distinguishing between 120-150 different coffee varieties at various roast levels. Crafting the perfect roast profile is an art that takes years to master, much like a painter perfecting their brushstrokes. Just as an artist creates masterpieces on canvas, a roast master crafts coffee masterpieces in the roastery.

Even from this short description, it’s clear — an expert roast master is invaluable.

The Roasting process

Appearances can be deceiving: visually identical roasted coffee beans can taste dramatically different. Each bag of coffee tells a unique story, influenced by the region where the coffee was grown, the altitude of the plantation, soil composition, harvesting methods, drying and storage conditions, transportation, and, most importantly, the roasting process.

During roasting, chemical reactions within the beans develop their flavor and aroma potential. The process can be divided into several key stages:

• Drying phase (up to 150°C)

• Maillard reaction (starting at 130°C)

• Caramelization (from 150°C to 170°C)

• Development time (from the first crack to the end of roasting)

A professional roast master controls these stages to highlight the strengths of each bean and unlock its full potential. The quality of the roast depends on the knowledge and intuition of the person “behind the wheel.”

Roasting cecrets

Here are some insights from our expertise:

• The drying phase should not exceed 4:30 minutes at 150°C to ensure optimal chemical reactions and maximum flavor retention.

• The total roasting time should not exceed 12:30 minutes for espresso and 11 minutes for filter coffee.

• Espresso and filter coffee require different roast profiles. Filter coffee is roasted lighter, typically at 205°C, while espresso is roasted at 211°C.

• Green beans should be free of defects, harvested no later than the previous year’s crop, and stored at 55% humidity and 20°C.

• Roasted beans should be filtered to remove “quakers” (underdeveloped beans) that can negatively impact flavor.

• We prioritize a longer development time after the first crack—between 1:30 and 2:30 minutes—resulting in a vibrant, sweet coffee with naturally embedded flavor notes.

These roasting “tricks” have been carefully refined based on feedback from our customers, championship judges, and our own preferences. The meticulous work pays off in the satisfied faces of our guests—proof that every effort is worth it!

Crack and Quakers: the science behind roasting

Roasting coffee isn’t just about tossing beans into a machine and waiting for the result. It’s a complex, multi-stage process, where beans transition from one phase to another, marked by a key moment known as the “crack.” When heated, the beans expand and literally crack due to internal pressure.

A roast without cracks is like a pumpkin spice latte without pumpkin—it’s just not right! The number of cracks determines the roast level:

• First crack (Light roast): When the temperature in the roaster nears 200°C, the beans pop, resembling the sound of popcorn popping. Beans at this stage are ideal for brewing filter coffee.

• Medium roast: Between the first and second crack, the coffee develops a balanced flavor with reduced acidity.

• Second crack (Dark roast): If roasting continues beyond the first crack, sugars caramelize further, and the bean structure begins to break down. At around 224°C, a second crack occurs, producing a darker roast with woody and smoky notes—perfect for those who enjoy intense espresso.

Even after turning off the roaster, residual heat can continue roasting the beans for up to a minute if not cooled quickly. Additionally, it’s crucial to monitor quakers—immature beans that appear lighter in color. If left in the mix, they can impart undesirable flavors like peanuts, wood, grass, or paper.

At Unity Coffee Roasters, we don’t rely on a modern-day Cinderella to hand-sort beans. Instead, we use a color sorter, an advanced machine that meticulously filters out imperfect beans, ensuring only the highest quality coffee reaches your cup.

Beyond Nature: what else affects coffee flavor?

Roasting stages change rapidly—mere seconds can separate one stage from another. After the first crack, the process accelerates significantly, making it crucial for roast masters to pinpoint this moment precisely. If a coffee is “underdeveloped,” it will retain grassy or papery flavors and lack depth. Conversely, if the development time is too long, notes of caramel, chocolate, nuts, and tobacco will dominate.

Our roast masters tailor the roasting time for each coffee variety based on bean density, acidity, sugar content, and overall flavor potential.

Both time and temperature influence how flavors are revealed. If plotted on a graph, time and temperature form a triangle — the “development area”. Adjusting these factors allows for diverse flavor profiles. The post-crack duration affects sweetness and body, while temperature impacts acidity and brightness. The intensity of the crack itself also influences the final cup — stronger cracks often indicate more vibrant flavors.

A skilled roast master considers plantation altitude, bean density, moisture content, variety, processing method, and even ambient humidity to predict how the beans will behave before they even reach the cupping table.

The Roast Master: an artist, analyst, strategist

Roasting is both an art and a science. A great roast master must balance creativity with analytical precision, taking into account numerous variables to determine the best strategy for unlocking each coffee’s full potential. The result? A perfectly roasted coffee that brings out the very best in every bean, cup after cup.

Coffee is more than just a drink — it’s an art, and its flavor is directly influenced by the skill of the roast master. Every stage of roasting, from the first chemical reactions to the crucial crack, plays a role in unlocking the bean’s full potential. That’s why at Unity Coffee Roasters, we pay close attention to every detail, from sourcing high-quality beans to fine-tuning roast profiles. The result is vibrant, rich, and well-balanced coffee that delights our guests. After all, every sip is a testament to dedication, expertise, and a true passion for the craft!