Drying, Maillard, and Caramelization: Different types of heat mean different cups of coffee

When coffee roasting is a craft, like it is for us, every detail matters.

Creating great coffee consistently means paying attention to each coffee’s roast profile: an account of what happened during the roast to affect the outcome (the final aroma and flavor).

Moving to our new location meant shifting from propane to natural gas as the fuel source for our roasting. This led us to create new roast profiles for every bean we roast!

Our shining star, the Diedrich IR-2.5, roasts up to 5.5lbs of coffee per batch. That’s small-batch! And with each one, we’re paying attention to every detail, including the way fuel source affects the overall flavor.

In order to develop a roast profile for a particular bean, we need to understand each roasting phase and how that phase of the roast affects the outcome.

Keep reading to learn what takes place in the coffee roasting process, and how the process affects the end-product: that delightful cup of small-batch coffee.

Propane vs. natural gas

Propane is controlled on the Diedrich roaster by increasing or decreasing the fuel pressure. Unlike your gas stove at home, there are no “high, medium, or low” temperature settings on the Diedrich.

Previously, we used propane to fuel our roaster; for each bean, we created a roast profile based on a pressure scale of 1-10: the standard propane scale. Natural gas has a standardized pressure scale of 1.5 to 7.

Since the scales are different, we roasted every one of our beans using natural gas while recording pressures at the appropriate times. 

We roasted all our beans, cupped them (tasted to be sure they’re still delicious!) and recorded the new settings, creating a new roast profile for each roast.

Drying, Maillard and Caramelization

There are three phases of a roast profile: Drying, Maillard, and Caramelization/Pyrolysis. 

Each of these phases requires heat, air, and time. Moving from propane to natural gas changes the ‘heat’ requirement. During each of these phases of roasting, heat is created in the drum roaster.

Drying Phase

This initial step is also known as the ‘Prep’ phase. Green beans are dropped into the roaster at the correct temperature in order to provide the correct amount of energy to begin the drying-out process.

When the temperature of the bean equals the temperature of the roasting drum, that’s called the turning point. The heat continues to ‘dry’ the bean as the temperature rises in the drum. All the heat from this activity is called conduction heat.

Maillard Phase

When the beans begin to turn yellow inside the drum, they’ve reached the point where convection heat is occurring along with conduction heat. At this point, we turn down the gas pressure to lower the heat, allowing the Maillard reaction to start.

One of the most important flavor-producing reactions in cooking is the Maillard reaction.

The Maillard reaction is a chemical reaction between amino acids and simple sugars that gives browned food its distinctive flavor.

Brown butter, anyone?

At this point in the roasting process, we’re now developing body, sweetness, and flavor in the coffee bean.

Caramelization Phase

This is the final stage of the roasting process. In this phase, there are many reactions happening, each relying on each other all at once:  first crack, sugar caramelization and organic acid degradation.

The Maillard reaction sparks sugar caramelization, when the sugars in the coffee bean start caramelizing: the sugar browns and releases aromatic and acidic compounds. Longer roasts allow for more of this organic acid degradation, and the end-result is a less bitter tasting coffee.

First crack is the point in the roast when the bean actually cracks internally, releasing sugars. This occurs in a temperature range of approximately 370-390°F and brings about distinct changes in taste and aroma. At this point in the roast, we turn down the gas pressure, reducing the heat even more. Now, the beans are basically roasting themselves from the inside, hence, heat being produced during this phase is called radiant heat.

The process is what makes roasting a craft

Developing our profiles at Rubicon Roasting involved many, many hours of roasting, recording the process, tasting (cupping) the roast, and re-doing it as many times as necessary to develop the desired taste.

We hope you enjoy ALL of the various roasts we have for you!