Winemaking with grapes affected by Botrytis cinerea
Botrytis cinerea is a weather driven fungus which causes the grapevine diseases botrytis bunch rot and grey mould.
The ideal conditions of its development are humidity, high crop density, and important vegetation development with the following consequences:
- Poor juice yields.
- Low must nitrogen and vitamins content, due to the consumption by Botrytis cinerea for its own growth.
- Unwanted microorganism development due to grape berry cell walls degradation.
- Must browning and oxidation by botrytis polyphenol oxydase: laccase.
- Filter clogging by Botrytis glucans.
GENERAL RECOMMENDATIONS
- Minimise the quantity of mould-affected fruit at harvesting.
- Add more sulfur dioxide (SO2) than usual due to the increased risk of oxidation from laccase and to limit population of other unwanted microorganisms.
- Bentonite fining to remove the laccase, PVPP to remove polyphenols.
- Tanins’ addition allows minimizing oxidation by laccase at early stage.
- Vigorous yeast and nitrogen addition are necessary
- Beta-glucanases ease filtration and increase filter cycles.
- Lysozyme addition offers an additional security.
Making white wines : In order to reduce the off flavors and eliminate the polyphenol oxydases, clarify severely and rack the wines as soon as possible. Used after pressing, pectinases break down long pectin chains and allow for faster clarification and compact lees settling.
Making red wines : Reduce harvest manipulations to the minimum in order to slow down the damages caused by the laccase. Ban delestages, avoid puch downs, and prefer pumping overs. The use of enzymes promotes polyphenol extraction with less physical manipulations.
With infected grapes, maceration duration must be reduced by 20 to 50%. Using extraction enzymes on red grapes will accelerate the release of phenolic compounds.
Use BIOPROTECTION to control unwanted microortanisms in conjunction with standard winemaking practices such as SO2 and tannins. Please see the below protocol for details.
Download this Botrytis Cinerea Information Sheet as a PDF.
