How to adjust the roasting curve to own the right batch of coffee

The roasting curve is a line that depicts the rise and fall of the roasting temperature per minute, displayed on a roasting chart. Each type of coffee will have different roasting charts and roasting curves.

They are often viewed by roasters as a tool for monitoring the temperature in the oven, helping them create a guide to recreate the roast profile for each individual coffee or flavor profile. For example, high-density coffee like Kenya will require a higher inlet temperature than wild Ethiopian coffees.

The roasting curve also shows the level of heat required for the stages that coffee goes through in the roasting process such as drying, first crack, second crack, etc., based on the sample roasting profile. If there is a standard profile, roasters will be able to complete the batch of coffee faster, right, save time, and avoid mistakes that damage the coffee. In addition, by applying the same amount of heat, the roasting curve for each roast also helps the batches of coffee to be uniform in flavor and color after roasting.

Choose the correct charging temperature

To roast coffee properly, you need to pay attention to the charging temperature according to the roasting curve displayed on the screen. This temperature indicates the amount of energy inside the drum to start roasting or the internal temperature level before you put the coffee in. The charging temperature should match the roasting curve you want to follow.

If the charging temperature is too low, you won’t have control over the reference roasting curve and have to heat up quickly at the Maillard stage, says Anne Cooper, a roasting consultant at Equilibrium Master Roasters. This will cause the coffee to have less flavor development and a grassy smell. If the charging temperature is too high, the machine will generate too much heat in the drum and burn the coffee creating a burnt, smoky and spicy smell.

Temperature management in the Mallard phase

The Maillard stage occurs when the heat reaches maturity and begins to promote chemical reactions in the coffee beans. At that time, the carbohydrates and amino acids in the coffee beans interact with each other, creating dark brown Melanoidin molecules. These molecules not only change the color of the coffee beans but also give the coffee its flavor and character.

To get the best coffee, you should pay attention to the duration of the Maillard phase, tracking on a roasting curve.

The famous coffee roaster, Rob Hoos, advises that to get the best coffee, you should closely monitor the changes of the Maillard stage on a roasting curve. Because if the time of the Maillard process is too short or too long, it will lose the characteristics of the coffee. At the same time, prolonging this period for too long can make the coffee taste bitter and salty.

Controlling the heating in the crack stages

Coffee beans begin to crack (first crack) after the Maillard stage. This is the time when heat and pressure make the substances in the particles resonate to the maximum extent, the outer shell is not enough to make them expand and expand, releasing water vapor and carbon dioxide. At this point, the roaster must adjust the temperature so that the roasting curve quickly reaches the first crack compared to the reference curve and stops early to create a light, fresh and herbal flavor.

After cracking, the coffee beans enter the growing phase, which lasts until the end of the roasting process. Controlling the development of a longer roasting curve will shorten the Maillard period, resulting in a more sour and sweet coffee.

At the end of the roasting process, the time it takes for the beans to first crack will have a marked effect on the caramelization, acidity, sweetness, and overall flavor of the beans. The shorter the time, the brighter and less carmelized the flavor can be. Over time, the flavor will “evolve” or turn brown, caramelized, and less bright. This is also the time when the heating rate of the grain can decrease too quickly or drop below zero causing flavor imbalance. Therefore, roasters need to pay attention to monitoring the roasting curve and provide enough heat even at the end of the process to ensure the perfection of the coffee batch.

At this point, you probably already know the importance and basics of how to adjust the roasting curve to get the right batch of coffee to your taste. Come to XLIII Coffee to immediately experience the cup of roasted specialty coffee and learn more great things in the world of specialty coffee!

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