Efficacy of Dimethyl Dicarbonate Against Yeasts Associated with Washington State Grapes and Wines

Efficacies of dimethyl dicarbonate ( DMDC ) against yeasts associated with grapes and wines were evaluated. Addition of the legal limit of DMDC (200 mg/ L ) to grape musts initially inoculated with 10 2 cfu/m L (low population) or 10 5 cfu/m L (high population) of C andida californica , C . oleophila , M etschnikowia pulcherrima , M eyerozyma caribbica , M ey. guilliermondii , S accharomyces cerevisiae or W ickerhamomyces anomalus resulted in declines of several logs. However, populations in excess of 10 6 cfu/m L were observed within days regardless of the initial inoculum. In contrast, culturability of Z ygosaccharomyces bailii inoculated into grape must (low populations) or wine (low or high populations) did not recover after treatment with DMDC . In wines, low populations of B rettanomyces bruxellensis   I 1a or E 1 declined after DMDC addition while culturability returned for F 3 no matter the initial inoculum. Treatment of wines using commercial dosing equipment resulted in a gradual loss of culturability of B rettanomyces when inoculated at 10 4 cfu/m L while the concentrations of volatile phenols remained unchanged after >3 years of storage. Practical Applications Upon exposure to dimethyl dicarbonate ( DMDC ), initial loss of culturability was noted for several yeasts, most dramatically for Z ygosaccharomyces bailii present in wine. Conversely, species of C andida , M etschnikowia , M eyerozyma , S accharomyces and W ickerhamomyces examined achieved high populations in grape must within a few days after application. DMDC was generally effective against B rettanomyces under laboratory and commercial scale conditions but differences between responses were noted between strains. Although the additive initially reduced culturable populations, DMDC did not completely eradicate yeasts present in grape musts or wines and therefore may not provide long‐term microbiological stability.