Harvest ToolkitJanuary 29, 2019
A few helpful tips to aid you in dealing with contaminated fruit
“Mouldy”, “phenolic” and “iodine-like”- not quite the attributes one would like to be used to describe their wine, these are, however, some of the unpleasant aromas associated with wines produced from Botrytis infected fruits. Unfortunately, the damage doesn’t stop there. Botrytis infected grapes are known to support larger populations of spoilage yeast and bacteria, further effecting the aroma of wines as these spoilage microbes produce ethyl acetate, acetic acid and other off-aromas.
Botrytis also produces the oxidative enzyme laccase, resulting in juices and wines with a higher sensitivity to oxidation, which may continue to have a negative influence on wines even after fermentation resulting in premature ageing, browning in white wines and colour instability in red wines.
Various other challenges may arise when making wine with Botrytis infected grapes.
• High pH and low TA grapes
• Production of glucans by Botrytis causing clarification and filterability issues
• Loss of varietal characters due to mouldy off-flavours
• Increased risk of stuck/sluggish fermentations due to yeast nitrogen deficiencies
• Increased risk of protein instabilities in wine
• Higher levels of bound SO2
• Production of Ochratoxin A, contributing to the risk of stuck/sluggish fermentations
• A final wine product lacking volume, balance and mouthfeel.
It is, therefore, imperative for winemakers to adjust winemaking practices when handling botrytis infected fruits. The main aim, of course, would be to minimize oxygen exposure and try eliminating laccase activity.
Not sure what steps to follow?
Copies of the poster available at Vinlab to all clients!