New Study Discovers Universal Color Curve for Arabica Coffee Roasting

In a groundbreaking study published in *Scientific Reports* on July 29, 2025, researchers from the University of California, Davis (UC Davis) have unveiled a universal color development curve for Arabica coffee during the roasting process. This significant finding promises to revolutionize quality control and standardization within the coffee industry.

Historically, coffee roasting has been viewed as a blend of science and artistry, where skilled roasters rely on visual, auditory, and olfactory cues to determine the ideal roast. However, the research conducted by a team led by Irwin R. Donis-González, an Associate Professor of Cooperative Extension in Postharvest Engineering at UC Davis, highlights a systematic and quantifiable method to evaluate roast levels through color analysis.

The study's methodology involved using a commercial drum roaster to systematically vary temperature ramp rates, examining the effects on color development throughout the roasting process. Over a period of sixteen minutes, the researchers tested seven distinct roasting profiles, sampling the coffee every minute and creating a high-resolution dataset that depicts color changes in the L*a*b* color space, a scientific color system designed to align with human visual perception.

According to Donis-González, "Color isn’t just about appearance; it’s a key indicator of quality for many products, including coffee." The research reveals that all Arabica coffee samples, regardless of the roasting dynamics or geographic origin, followed the same fundamental pathway in color development. The polynomial equations established in the study could predict color coordinates with over 93% accuracy, showcasing the reliability of the universal color curve.

Furthermore, the researchers validated their findings by conducting a systematic review of 20 different publications that encompassed various roasting methods and coffee origins, confirming that 86% of data points aligned with their universal curve. This consistency not only applies to coffee but also suggests broader implications for other food processing applications, such as bread baking, where similar Maillard reactions are involved.

The implications for the coffee industry are profound. Currently, there are no universally accepted standards for terms like "light roast" or "dark roast," leading to consumer confusion and inconsistencies along the supply chain. This universal coffee color curve offers a potential solution by providing a measurable way to assess roast levels, thus enhancing quality control across the industry.

As the research team continues to connect their findings with existing roast level scales, the hope is that this universal curve will facilitate a clearer understanding of roast levels among industry professionals. "We can now present the universal roasted coffee color to industry professionals, who can assist in categorizing and naming the colors of roasted coffee based on their experience and industry standards," noted Donis-González.

In conclusion, the discovery of a universal color curve for Arabica coffee roasting represents a pivotal advancement in coffee science. It not only promises to enhance quality control and standardization within the industry but also opens the door for further research into the complexities of food processing and flavor development. As the coffee industry moves towards embracing these scientific advancements, consumers can expect a more consistent and high-quality coffee experience in their cups.