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Fermentability of grape must after inhibition with dimethyl dicarbonate (DMDC)
Claudio Delfini1, Piero Gaia, Raffaella Schellino
1Istituto Sperimentale per l'Enologia, Sezione di Microbiologia, via P. Micca 35, 14100 Asti, Italy. sezione.microbiologia@tin.it
Abstract:
Dimethyl dicarbonate (DMDC) was added to grape must and to synthetic media and results showed that, at 20 degrees C, 150 mg.L(-)(1) DMDC completely inhibited the fermentation of a grape must that was previously inoculated with 10(6) cells.mL(-)(1) Saccharomyces bayanus and Saccharomyces uvarum. Brettanomyces intermedius, Candida guilliermondii, Hansenula jadinii, Hansenula petersonii, Kloeckera apiculata, Pichia membranaefaciens, and Saccharomyces cerevisiae were inhibited by 250 mg.L(-)(1). Candida valida was inhibited in the presence of 350 mg.L(-)(1), whereas Hanseniaspora osmophila, Saccharomycodes ludwigii, Schizosaccharomyces pombe, and Zygosaccharomyces bailii required 400 mg.L(-)(1). Delay of fermentation (but not inhibition) was noted in the presence of 400 mg.L(-)(1) for the following cultures: Brettanomyces anomalus, Hanseniaspora uvarum, Metschnikowia pulcherrima, Schizosaccharomyces japonicus, Torulaspora delbrueckii, and Zygosaccharomyces florentinus. Acetobacter aceti and Lactobacillus sp. were completely inhibited using 1000 and 500 mg.L(-)(1) DMDC, respectively. The fermentation of a grape must inoculated with 10(6) cells.mL(-)(1) of different wine yeasts was delayed for 4 days after the prior addition of 200 mg.L(-)(1) of DMDC; 200 mg.L(-)(1) DMDC did not show any residual inhibitory effect after 12 h, nor did 300 mg.L(-)(1) 24 h after the addition. In cellar experiments, indigenously contaminated grape musts (with and without skins) showed a delay in fermentation of 48 h after the addition of only 50 mg.L(-)(1) DMDC. The possibility of using DMDC (as pure grade as commercially available) in grape must as a disinfectant for the decontamination of musts indigenously contaminated with wild yeast should be considered seriously, despite its apparent low solubility in water.
Insights
Dimethyl dicarbonate (DMDC) effectively inhibits or delays wild yeast fermentation in grape must. Even low concentrations of DMDC show significant antimicrobial activity, suggesting its potential as a must disinfectant.
Area of Science:
- Enology
- Microbiology
- Food Science
Background:
- Wild yeasts and bacteria can negatively impact wine fermentation and quality.
- Controlling microbial contamination in grape must is crucial for successful winemaking.
Purpose of the Study:
- To evaluate the efficacy of Dimethyl dicarbonate (DMDC) as a potential disinfectant for grape must.
- To determine the inhibitory concentrations of DMDC against various wine-relevant microorganisms.
Main Methods:
- DMDC was added to grape must and synthetic media inoculated with different yeast and bacterial strains.
- Fermentation inhibition and delay were assessed at various DMDC concentrations and incubation times.
- Cellar experiments were conducted using indigenously contaminated grape musts.
Main Results:
- DMDC demonstrated dose-dependent inhibition of Saccharomyces and other wild yeasts, with concentrations ranging from 150 to 400 mg/L.
- Lower concentrations (50-200 mg/L) caused fermentation delays, with effects diminishing over 12-24 hours.
- DMDC effectively inhibited spoilage bacteria like Acetobacter aceti and Lactobacillus sp.
Conclusions:
- DMDC shows significant potential as a disinfectant for grape must decontamination.
- Its ability to inhibit or delay wild yeast fermentation warrants serious consideration in winemaking practices.
- Further investigation into DMDC's low solubility and residual effects is recommended.