Thyme and oregano essential oils reduce adhesion of spoilage yeasts isolated from beverage processing environments

Essential oils (EOs) have emerged as promising alternatives to conventional sanitizers. Although their antifungal activity has been widely reported, studies on application as sanitizers in food processing environments remain limited. This study evaluated the adhesion capacity of seven yeast strains, specifically Wickerhamomyces anomalus and Pichia kudriavzevii, isolated from a beverage processing line. It also investigated the potential of oregano and thyme EOs, applied individually or in combination, to inhibit fungal growth and cell adhesion.

Antimicrobial activity of essential oils was assessed by minimum inhibitory concentration (MIC) using RPMI 1640 medium in 96-well microplates. Cell adhesion was evaluated by crystal violet colorimetric assay and viable cell recovery in 24-well microplates. Measurements were taken after 24 and 48 h at 25°C. Anti-adhesion potential of essential oils was evaluated at subinhibitory and inhibitory concentrations, determining percentage inhibition. For strains with the highest adhesion capacity, their adhesion abilities and the effects of essential oils were analyzed by fluorescence microscopy after 48 h incubation. Results revealed high adhesion capacity, particularly for W. anomalus. All strains were susceptible to EOs in different concentrations. The oregano-thyme blended EO was the most effective, with MICs ranging from 0.38 to 1.52 $mg.m{{L}^{ - 1}}$ and significant reductions in cell adhesion, confirmed by viable cell recovery.

Current study findings suggest that EOs, especially the oregano-thyme blend, are a promising strategy to reduce yeast persistence on abiotic surfaces, as their ability to inhibit fungal growth and cell adhesion reinforces their potential as natural sanitation agents for beverage processing environments.