Paul van der Merwe, Anita Oberholster,* Lucy Joseph, and Linda Bisson 
*Department of Viticulture and Enology, University of California,
Davis, CA 95616 (aoberholster@ucdavis.edu)

Cleanliness and sanitation are inherent parts of winemaking and are necessary to reduce microbial populations throughout the winery. If microbial populations are ineffectively controlled, detrimental effects can occur that impact wine quality, ageability, or wine appearance through problems such as cloudiness, off-odors, or gas production. This study assessed survival of wine microorganisms at contact times applicable to tank cleaning protocols. Past studies have been more general, looking at model organisms or pathogens not found in the wine environment. Iso-lates of common wine microbes were studied, including Saccharomyces cerevisiae, Brettanomyces bruxellensis, Zygosaccharomyces bailii, Oenococcus oeni, Acetobacter pasteurianus, Pediococcus parvulus, and Lactobacillus casei. The sensitivity of plank-tonic cells and biofilms to each agent was examined. These microbes were tested against commonly used chemicals, with an emphasis on “green” chemical alterna-tives, at concentrations relevant to wine tank cleaning regimes at different contact times, which ranged from 5 to 30 min. Chemicals tested included sodium and potassium hydroxide and citric acid, and less environmentally harmful chemicals, including hydrogen peroxide, peracetic acid, and potassium bisulfate. Analysis of planktonic cells showed that sodium and potassium hydroxide were most effective in significantly reducing microbial populations in all organisms studied, while the other chemicals tested were shown to have mixed efficacy.

Funding Support: Unfunded research