Natural versus Saccharomyces boulardii self-induced anaerobic coffee fermentation: Effects on physicochemical properties and microbial ecology, and their influence on volatile profiles and sensory attributes across roast levels

This study investigates the effects of natural self-induced anaerobic fermentation (NSIAF) and Saccharomyces boulardii self-induced anaerobic fermentation (SSIAF) on Arabica coffee during wet processing. Over 24 h of fermentation, NSIAF exhibited greater microbial diversity, higher titratable acidity, and increased reducing sugar consumption, while SSIAF provided a more controlled microbial environment dominated by S. boulardii. Volatile compound analysis identified 207 compounds, with lighter roasts showing the greatest number of significantly different compounds between NSIAF and SSIAF treatments. Sensory evaluation revealed a higher cupping score for NSIAF at a light roast (82.08 ± 0.14) compared to SSIAF (81.58 ± 0.14), reflecting distinct flavor charac­ teristics imparted by each fermentation process. Both methods achieved specialty coffee standards (≥80 points), highlighting the potential of NSIAF for complex and diverse profiles and the suitability of SSIAF for consistency and controlled fermentation.