Utilizing malolactic fermentation as a tool to prevent Brettanomyces bruxellensis wine spoilage
Brettanomyces bruxellensis is considered one of the most problematic wine spoilage yeasts due to the difficulty of controlling it, the potential significant financial losses due to loss of wine quality, and the cost of prevention and remediation measures. Wine is particularly vulnerable to B. bruxellensis infection during and shortly after the malolactic fermentation (MLF) as SO2 cannot be added until this process is complete. It has been suggested that conducting a rapid MLF initiated by inoculation of Oenococcus oeni is a useful strategy to prevent B. bruxellensis spoilage as this minimizes the length of time the wine is not protected by SO2. This project investigates an additional benefit of conducting a rapid MLF, the prevention of B. bruxellensis growth due to inhibitory interactions with O. oeni. Pinot noir wine (no SO2 additions, no MLF) was produced and used to test the ability of a large number of commercial O. oeni strains to inhibit B. bruxellensis growth at the end of MLF. Sterile filtered wine was inoculated with one of eleven commercial O. oeni strains and growth and malic acid monitored. When MLF was complete, wines were inoculated with a select strain of B. bruxellensis and growth and volatile phenol production monitored.
All O. oeni strains tested inhibited the growth of B. bruxellensis UCD2049 in Pinot noir wine with O. oeni strain variation observed. O. oeni strains Alpha, 350, VP41, MBR31 and PN4 most strongly inhibited growth of B. bruxellensis UCD2049, while strains CH11, Omega, Beta, and VFO 2.0 inhibited B. bruxellensis to a lesser extent. The sensitivity of a range of B. bruxellensis strains to O. oeni was also determined in 2018 Pinot noir using O. oeni strain Alpha. While B. bruxellensis UCD2049 populations declined rapidly when inoculated into wine that had just completed MLF with O. oeni Alpha, growth of the other B. bruxellensis strains tested was not impacted. Why B. bruxellensis strain UCD2049 is sensitive to O. oeni while the other B. bruxellensis strain were not is unknown at this point but is being investigated in ongoing experiments. Additional experiments are underway exploring how long MLF induced B. bruxellensis inhibition last as well as whether B. bruxellensis inhibition occurs if infection happens at the beginning or mid-point of MLF. The mechanism of inhibition is also being investigated to determine if inhibition occurs via cell to cell contact, nutrient depletion, and/or production of an inhibitory compound by O. oeni. While wineries must continue to use sound winemaking practices to prevent the growth of Brettanomyces, results from this study may provide winemakers with an additional strategy/tool to help prevent wine spoilage by Brettanomyces.