Home / Library / Dealing with Botrytis: Analysis and Tools to Improve Quality
 

DEALING WITH BOTRYTIS: ANALYSIS AND TOOLS TO IMPROVE QUALITY

An infection with Botrytis cinerea negatively affects grape quality and the resulting wine. Botrytis affected grapes have a very high risk for enzymatic oxidation due to laccase activity. This fruit can also have reduced sugar, acid and polyphenol levels.

Download PDF

Due to high humidity levels in parts of North America over the past weeks, some vineyards are showing signs of Botrytis infection. Early, fast and accurate determination of infection levels can be used for effective screening of vineyards, grape lots or juice and enables winemakers to adjust the winemaking process and minimize negative effects on final wine quality.

Impact of Botrytis Cinerea Contamination on Grape and Wine Quality
An infection with Botrytis cinerea negatively affects grape quality and the resulting wine. Botrytis affected grapes have a very high risk for enzymatic oxidation due to laccase activity. This fruit can also have reduced sugar, acid and polyphenol levels. It can also increase the risk of problematic alcoholic fermentations and increases levels of spoilage microbes. In addition to “moldy” off-flavor development and high SO2 binding, resulting wines have color, clarification, filtration and stability issues.

A Fast and Accurate Determination of Infection Levels: Gluconic Acid
Gluconic acid, one of the most important metabolites of Botrytis cinerea, is the best marker to estimate the level of infection and adapt the winemaking process. Vinquiry Laboratories by Enartis provides same day Gluconic Acid test results, as well as Gluconic Acid Test Kits from Vintessential Laboratories for in-house testing. Grapes considered healthy can have gluconic acid levels between 0.2-0.3 g/L. Levels up to 1.0 g/L indicate an initial fungus infection (O.I.V reference).

Gluconic Acid Analysis: $30.00 (Sample volume: 50 mL)
Vintessential Gluconic Acid Test Kit (30 tests): $195.00
Botrytis Panel (PCR for Botrytis, gluconic acid): $70 (Sample volume: 50 mL) 

Tools to Reduce Botrytis Impact on Quality
Laccase enzyme produced by Botrytis cinerea has been shown to have very detrimental effects on color and several other grape phenolics (Dubernet 1977). Sulfite has been shown to have a limited effect on laccase activity at reasonable levels (<200 mg/L) (Dubernet 1973)). However tannin has been shown to limit laccase activity (Dumeau 2004). Enartis Tan Antibotrytis and Tan Blanc have both been shown to significantly reduce laccase activity. One of the best tools to utilize for machine harvested fruit with potential Botrytis infection is the antioxidant blend AST. This blend has a synergistic combination of ascorbic acid, potassium metabisulfite and gallic tannin. When added to grapes, the synergistic action of AST limits laccase activity and prevents microbial spoilage. The activity of laccase has also been shown to persist after fermentation late into the ageing process (Somers 1989). Utilizing Stab Micro M or Stab Micro, has been shown to reduce laccase activity in juice and wine, respectively.

How to Adjust the Winemaking Process: Keys Steps

  • Hand harvest and sort contaminated grapes in the vineyard
  • Utilize enological tannins such as Tan Blanc or Tan Antibotrytis to limit laccase activity in machine harvested and crushed fruit or use blends such as AST
  • Limit skin contact to reduce extraction of off-flavors
  • Remove any spoilage microbes as soon as possible with Enartis Stab Micro M
  • In white and rosé wines, promote fast clarification to reduce off-flavors and toxins that can alter fermentation
  • We recommend the use of Zym Elevage, an enzyme with β-glucanase activity, to break down glucans and improve clarification and filterability, ideally in juice/must 

See our website for additional Winemaking Guidelines for Botrytis Infected Grapes:

The technical staff at Enartis is available to support you in interpreting results and adjusting your winemaking approach.

For any inquiries, please call us at (707) 838-6312.

 

 

 
back to top