Troubleshooting Your Wine
The faults and flaws and their analysis and resolution presented below are from my latest book, Modern Home Winemaking, where you can find additional information should you wish to explore these further.
UNPLEASANT SMELL OF GERANIUMS
DESCRIPTION
Geraniums are great flowering plants, much appreciated for their wonderful scents. But alas, a detectable geranium-like smell in wine is considered a serious fault.
CAUSES
The smell of geraniums is caused by the addition of sorbate (sorbic acid), used to prevent a renewed fermentation in wines with residual sugars, in wines which have a high population of lactic acid bacteria (LAB), either indigenous or due to a malolactic fermentation (MLF).
LAB metabolize sorbate into a compound known as hexadienol that then goes on to react with ethanol to form the culprit compound, 2-ethoxyhexa-3,5-diene, which imparts a strong, disagreeable (in wine) and irreversible odor of geraniums, detectable at 0.1 µg/L (ppb).
ASSESSMENT
This fault is easily detected from the strong, unpleasant smell of geraniums that masks other aromas.
REMEDIAL ACTIONS
This fault cannot be reversed or cured, and the wine is best discarded. Do not be tempted to blend it with another wine – you may be propagating the problem.
PREVENTIVE ACTIONS
Do not use potassium sorbate in any wine that has undergone MLF.
For wine that will be put through MLF, ferment to total dryness – no sorbate will be required as there will be no residual fermentable sugars and the wine will be microbially stable.
For those that have undergone MLF and which have residual fermentable sugars, the only options are higher doses of SO2 without sorbate and to drink the wine young and fairly quickly before SO2 levels drop below critical levels, or sterile filtration.