Interaction Among Microbiota, Chemical Composition, and Quality Variations in Coffea arabica Across Altitudinal...

Planting altitude is a critical environmental factor shaping the flavor quality of Coffea arabica. However, how altitude influences flavor through microbial dynamics and chemical transformations during wet processing remains poorly understood. This study systematically investigates microbial diversity during wet processing and the corresponding changes in non-volatile and volatile compounds in coffee beans from four elevations: 1000 m (A1), 1200 m (A2), 1400 m (A3), and 1600 m (A4). The results showed that fermentation significantly altered the dominant bacterial genera from Sphingomonas and Pleomorphomonas (before fermentation) to Weissella and Lactobacillus (after fermentation), while Cladosporium and Fusarium remained the dominant fungal genera. Notably, non-volatile compounds in de-pulping coffee beans and volatile compounds of roasted coffee beans showed significant differences. Among them, 57 (1000 m), 218 (1200 m), 133 (1400 m), and 173 (1600 m) differentially changed non-volatile compounds (DCn-VCs) belonging to lipids and lipid-like molecules, organic acids and derivatives, organoheterocyclic compounds, organic oxygen, phenylpropanoids and polyketides, benzenoids, and other classes were identified. The cupping score of roasted coffee beans increased with increasing planting altitude, and A4 exhibited a long-lasting aftertaste, mellow and full body with high sweetness, nutty, and flowery with 42 (A4 vs. A1), 27 (A4 vs. A2), and 26 (A4 vs. A3) volatile compounds showing significant variation across altitudes. Therefore, planting altitude significantly influences coffee flavor by reshaping microbial diversity and chemical composition during wet processing. High-altitude cultivation promotes desirable sensory characteristics, highlighting its potential for producing specialty-grade coffee.