Biosafety and Fermentation Performance of Wickerhamomyces anomalus Starter Cultures in Fully Washed and Modified Whole-Cherry Fermentation of Coffea canephora

Fermentation strongly influences coffee quality, yet spontaneous fermentation often results in inconsistent sensory profiles due to uncontrolled microbial dynamics. This study evaluated the biosafety and fermentation performance of two Wickerhamomyces anomalus starter cultures, YWP1-3 and UV22-2, for controlled Robusta coffee fermentation. Biosafety was assessed based on antifungal susceptibility, hemolytic activity, and cytotoxicity toward Caco-2 cells. The starters were subsequently applied at different inoculum levels (OD600 15–45) for 24–72 h using fully washed and modified whole-cherry processes. Both strains exhibited γ-hemolysis, but Caco-2 cell viability remained relatively high at low-to-moderate concentrations (≤12.5% v/v). Controlled inoculation influenced microbial population and physicochemical changes during fermentation; the modified whole-cherry process generally produced higher cup scores and more balanced sensory attributes than the fully washed process. Notably, at the highest inoculum level, W. anomalus YWP1-3 enhanced desirable chocolate, raisin, and sweet notes and improved mouthfeel. Overall, the results demonstrate that selected W. anomalus starters are associated with changes in culturable microbial populations and fermentation characteristics. Integrating controlled yeast inoculation with modified whole-cherry fermentation represents a promising strategy for improving fermentation consistency and the sensory quality of Robusta coffee.