Use of a plastic film to eliminate the cork taint of a contaminated wine – improvement of organoleptic quality

Cork taint, generally recognized by a musty or moldy off-flavor, is a serious problem facing the industry today when putting wines on the market. To assess the effectiveness of a food-grade plastic film in removing the compounds concerned, trials were carried out under real conditions. It was found that enological parameters as well as color are maintained, and there is no absorption of phenolic compounds or oak aromas. The plastic film improves the organoleptic quality of wines contaminated with haloanisoles, by reducing the concentration of compounds that give the cork taint and mask oaky and/or fruity aromas.

Consumer Wine Closure Preferences: The Role of Gender, Price, and Regional Preferences

This paper analyzes buying decisions when consumers consider the risk that a bottle of wine may be cork-tainted. Drawing on a sample of 804 subjects, we examine the role of gender, price level, and subjects’ country of origin and their personal cork-taint risk assessments. We find that women assess the cork-taint risk higher than men but are still more likely to buy bottles with cork closures. Young consumers from Asia are more risk-averse than people from Western countries. Gender and regional differences vanish for wines in higher price brackets. (JEL Classifications: C90, D12, L66)

Musty and Moldy Taint in Wines: A Review

The literature about musty and moldy taint—the so-called cork taint—in wines is varied because there are many different molecules involved in this wine defect. Chloroanisoles are the most relevant compound responsible for cork taint and of these, 2,4,6-trichloroanisole (TCA) is the most common, but 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA) can also be responsible of this defect. For other compounds involved in cork taint, geosmin and 2-methylisoborneol (2-MIB) are responsible for earthy off-flavor; pyrazines cause vegetable odors, and guaiacol results in smoked, phenolic and medicinal defects. Off-odors of mushroom in wines are caused by 1-octen-3-ol and 1-octen-3-one coming from grapes contaminated by bunch rot (Botrytis cinerea). The sensory aspects of these molecules are illustrated in this review. Generally, the most important cause of this wine contamination is the natural cork of bottle stoppers, but this is not always true. Different origins of contamination include air pollution of the cellars, wood materials, barrels and chips. A review of the possible prevention or remedial treatments to cork taint is also presented. The best solution for this off-flavor is to prevent the wine contaminations.

Fungal Diversity of Deteriorated Sparkling Wine and Cork Stoppers in Catalonia, Spain

Filamentous fungi are rarely reported as responsible for spoiling wine. Cork taint was detected in sparkling wine; therefore, we investigated fungal contamination as a possible cause of organoleptic alteration. Spoiled wine was filtered and membranes were plated onto potato dextrose agar (PDA). The cork stoppers used for sealing bottles were cut and also plated onto PDA. Fungal strains were phenotypically characterized and molecularly identified by sequencing of a fragment of the 28S nrRNA gene (LSU) and (occasionally) by other additional molecular markers. Twenty-seven strains were isolated and sixteen species were identified, all of them belonging to the phylum Ascomycota. The fungi isolated from wine were three species of Aspergillus section Nidulantes, a species of Penicillium section Exicaulis and Beauveria bassiana. Candida patagonica was isolated from both sort of samples, and the fungi isolated from cork stoppers were Altenaria alternata and Cladosporium cladosporioides. Surprisingly, most of the taxa recovered from the cork stoppers and/or wine were new to the science: a new genus (Dactylodendron) and seven new species belonging to the genera Cladophialophora, Dactylodendron, Kirschsteiniothelia, Rasamsonia, and Talaromyces. Future studies could let us know if these fungi would be able to produce compounds responsible for cork taint.

Recent Developments on the Origin and Nature of Reductive Sulfurous Off-Odours in Wine

Reductive sulfurous off-odors are still one of the main reasons for rejecting wines by consumers. In 2008 at the International Wine Challenge in London, approximately 6% of the more than 10,000 wines presented were described as faulty. Twenty-eight percent were described as faulty because they presented “reduced characters” similar to those presented by “cork taint” and in nearly the same portion. Reductive off-odors are caused by low volatile sulfurous compounds. Their origin may be traced back to the metabolism of the microorganisms (yeasts and lactic acid bacteria) involved in the fermentation steps during wine making, often followed by chemical conversions. The main source of volatile sulfur compounds (VSCs) are precursors from the sulfate assimilation pathway (SAP, sometimes named as the “sulfate reduction pathway” SRP), used by yeast to assimilate sulfur from the environment and incorporate it into the essential sulfur-containing amino acids methionine and cysteine. Reductive off-odors became of increasing interest within the last few years, and the method to remove them by treatment with copper (II) salts (sulfate or citrate) is more and more questioned: The effectiveness is doubted, and after prolonged bottle storage, they reappear quite often. Numerous reports within the last few years and an ongoing flood of publications dealing with this matter reflect the importance of this problem. In a recent detailed review, almost all relevant aspects were discussed on a scientific data basis, and a “decision tree” was formulated to support winemakers handling this problem. Since we are dealing with a very complicated matter with a multitude of black spots still remaining, these advices can only be realized using specific equipment and special chemicals, not necessarily found in small wineries. The main problem in dealing with sulfurous compounds arises from the high variability of their reactivities. Sulfur is a metalloid with a large valence span across eight electron transformations from S (−II) up to S (+VI). This allows it to participate in an array of oxidation, reduction and disproportionation reactions, both abiotic and linked to microbial metabolism. In addition, sulfur is the element with the most allotropes and a high tendency to form chains and rings, with different stabilities of defined species and a high interconvertibility among each other. We suppose, there is simply a lack of knowledge of what is transferred during filling into bottles after fermentation and fining procedures. The treatment with copper (II) salts to remove sulfurous off-odors before filling rather increases instead of solving the problem. This paper picks up the abundant knowledge from recent literature and tries to add some aspects and observations, based on the assumption that the formation of polythionates, hitherto not taken into consideration, may explain some of the mystery of the re-appearance of reductive off-odors.

Quantification of wine fault markers and their relation with risk factors

While there have been numerous studies on individual wine faults and their risk factors little is known about their incidence and overall relationship to risk factors when purchased. To assess this relationship 100 wines produced in Missouri were randomly selected from the approximately 2500 available for sale in 2015- 2016. The wines collected went under a battery of tests for selected wine faults, flaws and known risk factors for problem development. The physical assessments included in this study where visual faults such as haze, sediment, excess turbidity and fill height from top of the bottle. Volatile compounds related to Brettanomyces sp. infection and cork taint were quantified as well as the undesirable aromas compounds H2S and 1-octen-3-ol, and acetic acid. Additional risk factors for fault development such as low free SO[subscript 2], high pH (above pH 3.7) and residual sugar were also assessed. Tested risk factors have varied greatly with wines having a pH value from 2.97-4.11, and free and total SO[subscript 2] varying from 0-118 mg/L and 3.6-324.4 mg/L respectively. While none of the wines exceeded current US legal limits for SO[subscript 2], 6% ([plus or minus]15%, for all MO wines at 95% CI) exceeded EU limits for total SO[subscript 2]. Conversely, 84% of the wines did not meet the free SO[subscript 2] requirement of 0.8 ppm based upon pH. At a fault recognition >|10|[micro]g/L for H[subscript 2]S 23% of the wines exceeded acceptable levels being considered faulted with no significant differences between categorical variables (e.g. red or white wine, closure type, fill volume etc.). This study is only one small sub-set of one region; to best understand how this data fits in with the wine industry as a whole, additional surveys are warranted. However, there is no reason to believe that this region is any different than would be found elsewhere.