From Chemical Transformations to Cup Quality: Integrated Insights into Key Non-Volatile Compounds, Aroma-Active Compounds and Sensory Evolution During Continuous Roasting Stages in Yunnan Arabica Coffee

Although understanding aroma evolution during roasting is essential for optimizing roasting control and coffee quality, most studies have focused on only a few discrete roasting levels. In this study, high-performance liquid chromatography (HPLC), headspace solid-phase microextraction and gas chromatography–mass spectrometry (HS-SPME-GC–MS), and sensory evaluation were integrated to characterize changes in key non-volatile compounds, odor-active compounds, and cup quality of Arabica coffee from green beans (S0) through eight successive roasting stages (S1-S8). The results show that the total contents of soluble sugars and chlorogenic acids continuously decreased throughout the roasting process. Volatile compound (VOC) diversity increased until S5, while the total VOC concentration peaked at S7. A total of 47 VOCs showed OAVs > 1, and phenylethyl alcohol, furfuryl alcohol, furfural, phenol, and pyridine were identified as key discriminant markers. Cup quality improved progressively and reached its optimum at S4, characterized by balanced nutty, roasted hazelnut-like, and caramel-like notes, but declined thereafter as smoky and burnt–bitter characteristics intensified. The transition from S4 to S5 therefore represents a critical turning point in coffee aroma evolution during roasting. These findings provide a basis for optimizing roasting control and coffee aroma quality.