Can you distill wine defects away?
By: Denise M. Gardner
By definition, wine defects are typically undesirable and unpleasant characteristics that occur in wine as a function of poor viticulture, winemaking, or storage techniques. The words “fault” and “defect” can be used interchangeably.
Perception of wine defects varies from individual to individual, which emphasizes the importance of sensory evaluation training amongst winemakers. If a winemaker is genetically blind to sensing a specific defect, and there is no secondary personnel available to “double check” the wine, wines may be bottled and sold to consumers faulted.
However, several wine defects can also be evaluated analytically throughout various stages of wine production. This emphasizes an importance of understanding analytical evaluation of wine and how it relates to wine quality.
While there is a lot of pride that goes into being a winemaker, wine defects happen. To everyone.
Sometimes these defects may reach concentrations that throw the wine out of balance or are beyond traditional remediation techniques. In these instances, a winemaker may turn to the use of distillation to treat wine defects with the hope of producing a distilled spirit that does not retain the perceived defect.
Distillation is used as a technique to concentrate ethanol from a fermented beverage. Typical spirits are produced from low-alcohol grain- or fruit-based fermented beverages. Pure ethanol, which has a lower boiling point (78.5°C) than water (100°C), vaporizes prior to water when heated. This physical property allows the separation of ethanol from water when it is properly heated. However, fruit-based fermented beverages are complex mixtures, and separation of other components, like odorous aroma compounds, may also be separated from the initial beverage.
The table below outlines the boiling points of common wine defects.
Based on this table, one may assume that many of these components can be easily separated from ethanol and water in the base product. In fact, older research literature has shown the reduction of many aldehyde-based compounds, some associated with wine oxidation, in commercial brandies produced in California (Guymon 1970). However, several compounds including hydrogen sulfide, “reduced” sulfur-containing compounds, sulfur dioxide, 2,4,6-trichloranisole (TCA, cork taint), methoxypyrazines, and some Brettanomyces-related aromas may be concentrated and retained in the final distillate.
Separation of aromatic compounds (volatiles) is not based on boiling point alone due to the fact that the base material, wine, is a complex mixture. Separation of volatile components will also be based on the relationship that compound has with ethanol or water (Léauté 1990). Many of these compounds like TCA, methoxypyrazines, or sulfur-containing compounds may be present in the base wine in such low concentrations that it may be challenging to effectively separate from the ethanol. However, some distillers point to the use of a copper still to help interact with sulfur containing compounds (such as hydrogen sulfide or thiols/mercaptans) to reduce these aromas in the distillate. One study found that dimethyl sulfide (DMS) was reduced when a copper still was used for distillation as opposed to a non-copper still (Fairia et al. 2003).
Concentration is also a factor for things like TCA or many methoxypyrazines, which are commonly present in wine in part per trillion (PPT) concentrations. In a study that evaluated distilled hard apple cider, the researchers identified several descriptors by use of olfactometry associated with making the distillate “defective:” sweat, vegetal, phenolic, old sponge, pyrazin, solvent, rot, mold, and herbaceous (Guichard et al. 2003). While the source of these sensory descriptors was not linked to any one aroma compound, some of these terms, like herbaceous and vegetal may be associated with methoxypyrazines or other aldehydic aroma compounds. Old sponge, rot, or mold may be associated with TCA and other spoilage volatiles. The study by Guichard et al., however, exemplifies how human perception of distillate dictates perceived quality.
Previous research associated with 4-ethyl guiacol (4EG) has shown retention of this aromatic compound in the distilled component called “the hearts.” Volatile components retained in the hearts have low boiling points and are typically soluble in alcohol (Léauté 1990). Therefore, retention of this odor compound may be altered based on where a distiller makes his or her cuts for distillate retention. In the case of batch distilling, it may be possible to further reduce these compounds by re-distilling a batch several times.
Solutions for Winemakers
The overarching message pertaining to distillation to remediate wine faults is that is not a fix-all solution to “cure” wine defects. In some cases, the winemaker may go from dealing with a faulted wine to receiving a faulted distilled spirit.
Many base wines used for distilled spirits are selected for flavor neutrality and nuance. Wines that contain faults are likely to contribute some additional nuance flavors that may not be expected in the final distilled spirit. Winemakers need to make sensory decisions to determine if a potential unexpected nuance flavor in the distilled spirit would be considered detrimental to the quality of their final product. If so, remediating the wine defect through alternative means may be necessary.
As with many issues pertaining to wine defects, the best way to ensure quality is to try to avoid the defect before it occurs in the wine. Receiving high quality raw material (i.e. grapes), using proper sanitation techniques, and managing oxygen exposure during wine processing can help winemakers avoid many wine defects.
More Information on Distilling Wine Defects
Previous Penn State Food Science undergraduate student, Erin Donnelly, published her review pertaining to the use of distillation to “cure” wine defects. This paper was later refined and published in the March-April 2015 Vineyard & Winery Management trade magazine, titled “Distillation of Faulted Wines.” Both articles are great references for further information on this topic.
Guichard, H., S. Lemesle, J. Ledauphin, D. Barillier, and B. Picoche. 2003. Chemical and sensorial aroma characterization of freshly distilled calvados. 1. Evaluation of quality and defects on the basis of key odorants by olfactometry and sensory analysis. J. Agric. Food Chem. 51: 424-432.
Guymon, J.F. 1970. Composition of California commercial brandy distillates. Am. J. Enol. Vitic. 21(2): 61-69.
Faria, J.B., V. Ferreira, R. Lopez, and J. Cacho. 2003. The sensory characteristic defect of “cachaҫa” distilled in absence of copper. Alim. Nutr. 14(1): 1-7.
Léauté, R. 1990. Distillation in Alambic. Am. J. Enol. Vitic. 41(1): 90-103.