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Midwest Grape and Wine Industry Institute

Tartrate Crystal Precipitation-Wine Fault Series

Dr. Aude Watrelot, Jennie Savits, & Maureen Moroney | 2020

potassium bitartrate (KHT) crystals, also known as wine diamonds, are not harmful to consumers, but may be considered a visual defect of the wine in the bottle or glass. They may appear like salt crystals, glass shards, or fine dust. In red wines, they may be pigmented. Tartrate stability may be achieved by chilling or by contact seeding with chilling, both of which encourage KHT crystals to form and precipitate, so that the wine can be racked or filtered to remove them prior to bottling.

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Excessive Sulfur Dioxide-Wine Fault Series

Aude Watrelot, Jennie Savits, & Maureen Moroney| 2020

The excess of sulfur dioxide (SO2) in wine is an additive-related fault. It is the most important additive used to preserve wine at different steps of the winemaking process from harvest to bottling. To prevent this wine fault, the effective level of SO2 should be calculated based on the type of wine, the level of SO2 already present in wine, the level of compounds able to bind to SO2, and wine pH.

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Oxidation-Wine Fault Series

Dr. Aude Watrelot, Jennie Savits, & Maureen Moroney | 2020

The oxidation of wine is the most common of wine faults that occur throughout the winemaking process and after bottling. Oxidation of wine is associated with the browning and darkening of white and red wine color. In white wines, the clear yellow color will become dark gold or brownish while red wines will be brown or brick red. The smell and varietal aromas of the wines decrease and some bruised apple, nutty, or sherry-like aromas develop in the oxidized wines.

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Hydrogen Sulfide and Volatile Sulfur Compounds-Wine Fault Series

Dr. Aude Watrelot, Jennie Savits, & Maureen Moroney | 2020

Volatile sulfur compounds (VSCs) are a class of sulfur containing compounds that are often described as reductive or reduced. The most common of these faults is hydrogen sulfide (H2S), which smells like rotten eggs or sewer gas. Like many other compounds causing wine faults, H2S in trace amounts can add to the wine. When the concentration reaches or exceeds the sensory threshold, the odor can become a problem.

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Geranium Taint-Wine Fault Series

Dr. Aude Watrelot, Jennie Savits, & Maureen Moroney | 2020

Geranium taint is an additive related fault that can arise when sorbic acid, used as a preservative to inhibit yeast growth, is added to wine. Lactic acid bacteria (LAB) metabolize sorbic acid to produce a volatile compound smelling like crushed geranium leaves. Use sound winemaking practices to prevent bacterial spoilage and unwanted malolactic fermentation (MLF) by LAB.

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Spoilage by Lactic Acid Bacteria-Wine Fault Series

Dr. Aude Watrelot, Jennie Savits, & Maureen Moroney | 2020

Lactic acid bacteria (LAB), as a group, are involved in the fermentation of malic acid and can utilize other constituents in wine. Some LAB strains are connected to spoilage, while Oenococcus oeni species is well known for conducting malolactic fermentation (MLF). The LAB population is generally low on fruit…

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