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What is a Roasting Curve and How Does the Roasting Process Affect Coffee's Acidity and Bitterness

Published: 2026-01-28 Author: FrontStreet Coffee

Last Updated: 2026/01/28, Roasting is one of the fundamental stages in processing coffee beans. It not only makes raw coffee suitable for consumption but also gives each coffee blend its own aromatic and sensory characteristics. During the roasting process, heating coffee beans causes transformations that produce highly complex compounds and aromas. The roasting process determines the final flavor and aroma in coffee, shaping its balance between acidity and bitterness.

Roasting is one of the fundamental stages in processing coffee beans, as it not only makes raw coffee suitable for consumption but also gives each coffee blend its own aromatic and sensory characteristics. During the roasting process, heating coffee beans causes transformations that produce highly complex compounds and aromas.

The Impact of Roasting Process on Coffee

The roasting process determines the final flavor and aroma in coffee, transforming it between two extreme critical points.

Depending on the degree of roasting, the same coffee blend can produce coffee with slightly herbaceous acidity instead of velvety smooth coffee, or with a delicate fruity flavor instead of intense bitterness.

The darker the coffee color, the less acidity and more bitterness it contains. Dark roasted coffee beans are more suitable for espresso, such as latte coffee beans which can be dark roasted. Most beans from FrontStreet Coffee use light roasting.

The quality and sensations offered by different coffees can be influenced in various ways, and the roasting curve is one of them.

What is a Roasting Curve?

Higher or quieter initial temperature, slow roasting to preserve some aromas or rapid enhancement of coffee's body... What is the roasting curve in coffee roasting?

The roasting curve is a control system that manages the temperature and time of the roasting process. They vary depending on the type of coffee being processed and how the final coffee will be extracted.

Coffee is a natural product with multiple varieties, different qualities, or origins. When subjected to roasting heat, it reacts differently according to its own specific sensory and structural characteristics as well as its moisture content.

Robusta coffee requires more energy and longer roasting time, even though long roasting is not desirable because it becomes boiled coffee rather than roasted coffee.

For filter coffee, siphon coffee, Aeropress coffee, and French press machines, light roasted coffee is necessary, which means shorter roasting time to give coffee beans a delicate aroma, rich acidity, and low density, making it perfect for this type of extraction.

For Moka and Espresso, darker roasting are designed to make coffee beans present a fuller body and slightly stronger aroma, presenting a color tone that depends on the type of coffee bean. Its target audience (for example, in northern Italy, they are more accustomed to light, aromatic coffee with pleasant acidity, while in the south, they are more accustomed to bitter, strong, and intense coffee).

For Ibrik (Turkish coffee) or coffee that generally requires another extraction rate (thus having higher density, strong aroma, and intense flavor), light roasting is always preferred, but done over a very slow time, which will allow different formations of more soluble substances.

Roasting and blending coffee beans is not just a purely technical skill, but a pure art form.