How Do You Prevent Brettanomyces in Wine?

Preventing Brettanomyces in wine involves a comprehensive and multi-faceted approach centered on stringent winery hygiene, precise sulfur dioxide management, and strategic microbial control throughout the winemaking process.

Understanding Brettanomyces

Brettanomyces bruxellensis (often simply called "Brett") is a spoilage yeast that can negatively impact wine quality. It metabolizes residual sugars and other compounds, producing volatile phenols that contribute undesirable aromas such as "horse stable," "barnyard," "band-aid," or "medicinal." These off-flavors can mask desirable fruit characteristics and significantly diminish a wine's appeal.

Comprehensive Strategies for Brettanomyces Prevention

Effective prevention requires vigilance and a layered approach, as Brettanomyces is highly adaptable and resilient.

1. Impeccable Winery Hygiene and Sanitation

Brettanomyces can establish biofilms in almost any part of the winery. Thorough and consistent cleaning is paramount to eliminate potential reservoirs.

• Regular Cleaning: Implement a rigorous schedule for cleaning all equipment, including tanks, hoses, pumps, presses, and barrels, immediately after use.
• Appropriate Sanitizers: Utilize effective sanitizing agents like peroxyacetic acid, ozone, or steam. Ensure proper contact time and concentration.
• Attention to Detail: Pay special attention to hard-to-clean areas such as gaskets, valves, clamps, and any rough surfaces or cracks where biofilms can form.
• Dedicated Equipment: Consider dedicating certain equipment (e.g., hoses, pumps) to specific wine batches, especially if contamination is suspected.

For more information on winery sanitation, refer to resources like UC Davis's insights on sanitation.

2. Effective Sulfur Dioxide (SO2) Management

Sulfur dioxide is a primary chemical defense against microbial spoilage, including Brettanomyces.

• Initial Addition: Add SO2 to must or juice at crushing to inhibit undesirable wild yeasts and bacteria, giving commercial Saccharomyces yeast a competitive advantage.
• Maintaining Free SO2: Consistently monitor and maintain adequate levels of free SO2 throughout fermentation, aging, and bottling. Free SO2 is the active form that inhibits microbial growth.
• pH Adjustment: The effectiveness of SO2 is highly dependent on wine pH. Lower pH wines (typically below 3.6) require less total SO2 to achieve the same level of free SO2, as more of it will be in the active molecular form.
• Regular Monitoring: Test SO2 levels frequently, especially after additions, transfers, or significant temperature changes, and adjust as necessary.

Learn more about the role of SO2 in wine from resources like Cornell University's Viticulture & Enology program.

3. Proactive Microbial Management

Managing the wine's microbial ecosystem can actively prevent Brettanomyces growth by favoring beneficial microorganisms.

• Healthy Fermentations:
  • Use robust, commercially selected Saccharomyces cerevisiae yeast strains.
  • Ensure optimal fermentation conditions (temperature, nutrients) to promote a fast and complete primary fermentation, minimizing the time wine is vulnerable to spoilage.
  • Avoid stuck or sluggish fermentations, as residual sugars are a prime food source for Brettanomyces.
• Malolactic Fermentation (MLF) Control:
  • Co-inoculation (adding malolactic bacteria shortly after yeast inoculation) or rapid post-fermentation inoculation with selected malolactic bacteria strains is a proven strategy to control Brettanomyces development. This approach allows the full potential of the malolactic bacteria to be expressed, contributing to an appropriate sensory profile while quickly consuming malic acid and other potential nutrients that Brettanomyces might utilize.
  • Ensure MLF completes swiftly if desired. If MLF is undesirable, take active steps to prevent it entirely (e.g., chilling, SO2 addition, lysozyme).
• Competitive Exclusion: Encourage the growth of desirable wine microbes that can outcompete Brettanomyces for nutrients and space.

4. pH Control

Wine pH is a critical factor influencing both microbial stability and the effectiveness of SO2.

• Lower pH: Wines with lower pH (typically below 3.6) are generally more resistant to Brettanomyces growth. This is due to the increased activity of molecular SO2 at lower pH and a less favorable environment for the yeast itself.
• Acid Adjustment: If necessary, adjust must or wine pH through acidification to create a less hospitable environment for spoilage organisms.

5. Vigilant Barrel Management

Oak barrels, especially older ones, are notorious hiding places for Brettanomyces due to their porous nature and difficulty in thorough cleaning.

• Thorough Cleaning: After emptying, clean barrels rigorously with high-pressure hot water, steam, or specific barrel cleaning agents.
• Sanitization: Sanitize barrels with an appropriate solution (e.g., ozone water, sulfite solutions) between uses.
• Rehydration: If barrels dry out, rehydrate them properly, potentially with hot water or steam, to ensure sanitation deep within the wood.
• Proper Storage: Store empty barrels with a sulfur wick or an SO2 solution to prevent microbial growth. Store full barrels with adequate head space management and SO2.
• Segregation: If a barrel is known or suspected to be contaminated, segregate it or remove it from circulation entirely to prevent cross-contamination.

6. Regular Monitoring and Early Detection

Proactive monitoring allows for early intervention before Brettanomyces levels become problematic and cause irreversible damage.

• Sensory Evaluation: Routinely taste wines for characteristic Brettanomyces off-flavors (e.g., smoky, clove, antiseptic, horse stable). Training staff to identify these faults early is crucial.
• Microbiological Plating: Periodically sample wines and plate them on selective media (e.g., WLN agar) to quantify Brettanomyces populations.
• PCR Testing: Utilize rapid molecular methods (PCR) to detect Brettanomyces DNA even at very low populations, offering an early warning system.

Summary of Prevention Strategies

By integrating these strategies into a comprehensive winery protocol, winemakers can significantly reduce the risk of Brettanomyces spoilage and protect the quality of their wines.