Home / Library / Gluconic Acid Testing: A Decision Tool for Botrytis Infected Fruit
 

GLUCONIC ACID TESTING: A DECISION TOOL FOR BOTRYTIS INFECTED FRUIT

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.

Download PDF

Due to high humidity levels in California over the past weeks, some vineyards are already 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. Affected grapes have high sensitivity to oxidation due to the oxidasic enzymatic activity (laccase) and show a reduction in sugar, acid and polyphenol composition, and are often associated with problematic alcoholic fermentations and high spoilage microbe contaminations. 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 provides same day Gluconic Acid test results in all locations (Windsor, Paso Robles and Santa Maria), as well 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): $190.00

Botrytis Panel (PCR for Botrytis, laccase activity test, glucan screening, gluconic acid): $100 (Sample volume: 50 mL) 

How to Adjust the Winemaking Process: Keys Steps

  • Hand harvest and sort contaminated grapes in the vineyard
  • Use adequate antioxidant and antioxidasic protection to limit browning, color loss and oxidation of aromas
  • 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
  • In reds, promote fast extraction of polyphenols with Enartis Zym Color Plus
  • Select a resistant, aromatic and dominant yeast strain with low nitrogen needs
  • Implement a proper yeast nutrition strategy

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

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

Main Branch: (707) 838-6312 / Santa Maria Branch: (805) 922-6321 / Paso Robles Branch: (805) 591-3321

 

 
back to top