Tag Archive | Brettanomyces

Ensure Your Wines are Stable Before Bottling

By: Denise M. Gardner

It’s that time of year again: bottling time! The past year’s vintage is slowly starting to take up too much room in the cellar and now is the time for decision making in terms of preparing for the pending vintage.  Finalizing a good bottling schedule before harvest starts is an essential good winemaking practice, but bottling comes with its own set of challenges.

It is not uncommon for winemakers to express feelings of “not being able to sleep at night” when wines get bottled, as they are worried about possible re-fermentation issues.  As wine naturally changes through its maturity, it is easy to feel insecure about bottling wines, especially those wines that may have had challenges associated with it throughout production.

However, there are several analytical tests that winemakers can add to their record books every year to ensure they are bottling a sound product.  The following briefly describes a series of analytical tests that provide information to the winemaker about stability and potential risks associated with the product when it goes in bottle.

Bottling comes with its own set of challenges and risks, but several analytical tests can help put a winemaker’s mind to ease regarding bottle stability. Photo by: Denise M. Gardner

Basic Wine Analysis Pre-Bottling:

This first list is the bare minimum data that should be measured and recorded for each wine getting bottled, regardless of the wine’s variety or style.  Keeping accurate records of these chemistries is also helpful in case something goes wrong while the bottle is in storage or after it is purchased by a customer.

pH

pH is essential to know as it gives an indication for the wine’s stability in relation to many chemical factors including sulfur dioxide, color, and tannin.  For example, high pH (>3.70) wines provide an indication that more free sulfur dioxide is needed to obtain a 0.85 ppm molecular free sulfur dioxide content.  At the 0.85 ppm molecular level, growth of any residual yeast and bacteria in the wine should be adequately inhibited.

High pH wines tend to have issues with color stability.  At this point, color stability can be addressed by blending or with use of color concentrates (e.g., Mega Purple).  Keep in mind that if the wine is blended with another wine, all chemical analyses, including pH, should be completed on the blend (as opposed to average individual parts) prior to bottling.

Free and Total Sulfur Dioxide Concentration

In the United States, total sulfur dioxide is regulated and must fall under 350 mg/L for all table wines (CFR: https://www.ecfr.gov/cgi-bin/text-idx?SID=eddaa2648775eb9b2423247641bf5758&mc=true&node=pt27.1.24&rgn=div5#sp27.1.24.a).

However, the free sulfur dioxide concentration provides an indication to the winemaker regarding antioxidant strength and perceived antimicrobial protection.  To inhibit growth of yeast and bacteria during bottle storage, a 0.85 ppm molecular free sulfur dioxide concentration must be obtained.  The free sulfur dioxide concentration required to meet the molecular level is dependent on pH.  Therefore, free sulfur dioxide additions should be altered and based on a wine’s pH for optimal antimicrobial protection.

Analytically, it can be daunting to measure free sulfur dioxide as the wet chemistry set up looks intimidating.  However, many small commercial wineries have benefited from the integration of a modified aeration-oxidation (AO) system, and with a little practice, have been relatively successful at monitoring free sulfur dioxide concentrations.  A few wineries have worked to validate use of Vinmetrica’s analyzer (https://vinmetrica.com/), and found results comparable to those obtained by use of the AO system.

Residual (or Added) Sugar

Any remaining sugar in the bottle, whether through an arrested fermentation or direct addition, can pose a risk for re-fermentation post-bottling.  This is especially true if the winery lacks good cleaning and sanitation practices.  Nonetheless, it is a good idea to assess the sugar content pre-bottling to record a baseline value of the sugar concentration going into bottle.  If bottles were to start re-fermenting, a sugar concentration could be analyzed and used to compare against the baseline value in order to assess the potential of yeast re-fermentation.

For wineries with minimal residual sugar concentrations, a glucose-fructose analysis (often abbreviated glu-fru) is often used to help determine accurate sugar content.  For wines with added sugar an inverted glucose-fructose analysis may be required.

If you are concerned about potential risk for Brettanomyces (Brett) bloom post-bottling, it is usually encouraged to reduce the sugar content in the finished wine below 1% (<10 g/L sugar) in the bottle.

Malic Acid Concentration

While using paper chromatography to monitor malolactic fermentation (MLF) is useful, it does not give an accurate reflection of residual malic acid concentration.  In fact, some winemakers find that a paper chromatogram may show a MLF has been “completed,” but would prefer to have lower residual malic acid concentrations remaining in the wine.

During my time at an analytical company, 0.3 g/L of malic acid and below was considered “dry.”  This is typically a safe level of residual malic acid to avoid post-bottling MLF.

Volatile Acidity

Volatile acidity (VA) is federally regulated, and levels are indicated in the Code of Federal Regulations (CFR: https://www.ecfr.gov/cgi-bin/text-idx?SID=eddaa2648775eb9b2423247641bf5758&mc=true&node=pt27.1.24&rgn=div5#sp27.1.24.a).  For most states, with California as an exception, the maximum allowable VA for red wines is 1.40 g/L acetic acid (0.14 g/100 mL acetic acid) and for white wines is 1.20 g/L acetic acid (0.12 g/100 mL acetic acid).

Monitoring VA through production is a good indicator of acetic acid bacteria spoilage.  At minimum, wineries should record VA

  • immediately post-primary fermentation,
  • post-MLF,
  • periodically through storage (e.g., every 2-3 months) and
  • pre-bottling.

Whiling monitoring VA, sharp increases in VA should alarm the winemaker of some sort of contamination.  Typically, these increases are caused by acetic acid bacteria, which can only grow with available oxygen.

Alcohol Concentration

As a general rule of thumb, knowing the final alcohol concentration is a good idea.  Alcohol content helps determine a tax class for the wine and is required for the label.

 

Extra Analysis:

Titratable Acidity (TA)

All wines are acidic in nature as they fall under the pH 7.00.  However, titratable acidity (TA) acts as an indicator for the sour sensory perception associated with a given wine.  For example, two wines, Wines 1 and 2, with a pH of 3.40 may have different TAs.  If Wine 1 has a TA of 8.03 g/L tartaric acid while Wine 2 has a TA of 6.89 g/L tartaric acid, Wine 1 would likely taste more acidic (assuming all other variables are the same).

Titrations are an easy analytical testing method to learn and understand when testing wine’s chemistry. Photo by: Denise M. Gardner

Cold Stability

Cold stability tests are often recommended to ensure the wine is cold stable, and will, therefore, not pose a threat of precipitating tartrate crystals during its time in bottle.  Not all wines require a cold stability process (e.g., seeding and chilling).  Cold stability testing can be done prior to a cold stabilization step in order to avoid extraneous processing operations, saving time and money.

For more information on cold stability processes and testing, please visit Penn State Extension’s website: http://extension.psu.edu/food/enology/analytical-services/cold-stabilization-options-for-wineries

These crystals on this cork illustrate what can happen when a wine is not properly cold stabilized. While the tartrate crystals pose no harm to consumers, they may find the crystals unappealing or questionable. Photo by: Denise M. Gardner

Protein Stability

Additionally, haze formation is a potential risk post-bottling.  While hazes do not typically offer any safety threat to wine consumers, they often look unappealing.  Protein hazes tend to make the wine look cloudy.  Some varieties are more prone to protein hazes then others, and running a protein stability trial could minimize the risk for a protein haze in-bottle.

It is important to remember that due to the fact protein stability is influenced by pH, cold stability production steps should take place before analyzing the wine for protein stability and before going through any necessary production steps to make the wine protein stable.  This is due to the fact that cold stability processes ultimately alter the wine’s pH, and the chemical properties of proteins are influenced by the pH.

 

Analysis for Those that May Consider Bottling Unfiltered:

Yeast and Bacteria Cultures (Brett, Yeast, Lactic Acid Bacteria, Acetic Acid Bacteria)

Having a microscope in the winery can be a great reference point in terms of scanning for potential microbiological problems.  However, if the winery does not have a microscope, but knows that some microbiological issues or risks may exist in a wine, having a lab set test the wine on culture plates is a good indicator for potential growth risks during the wine’s storage.

If the wine is going to be bottled using a sterile filtration step, keep in mind that wines are not bottled sterile.  Assuming the absolute filtration method is working properly, the wine has potential to become re-contaminated with yeasts and bacteria from the point of which it exits the filter.  In fact, it is not uncommon for wines to pick up yeast or bacteria contamination during the bottling process.

Managing free sulfur dioxide concentrations can help inhibit any potential growth from contamination microorganisms if the proper antimicrobial levels (0.85 ppm molecular) are obtained at that wine’s pH and retained during the bottle’s storage.

4-EP and 4-EG Concentrations for Reds

For wines that may have had a Brettanomyces (Brett) bloom, knowing the concentrations of 4-EP and 4-EG in the wine going into bottle is a good result to keep on file.  If a Brett bloom occurs later in the bottle, it is likely (although, not guaranteed) that the volatile concentration of 4-EP and/or 4-EG may increase and confirm the problem.

Furthermore, evaluating a wine for 4-EP and 4-EG concentrations can also help isolate a possibility of Brett existence, especially if their concentrations are below threshold.  However, it should be noted that both compounds can also exist in wines that are stored in wood, even without a Brett contamination.

Double Check: PCR for Reds

Brett can be a tricky yeast to isolate and identify.  It is usually recommended to run multiple analytical tests related to Brett in order to confirm its existence or removal from a wine.  While culture plating identifies living populations of microorganisms, PCR cannot typically differentiate between live and dead cells as it is measuring the presence of DNA.  A microorganism’s DNA can get into a wine after yeast death and through autolysis.  Therefore, a positive PCR result for Brettanomyces is hard to confirm if the result includes live cells, dead cells, or a combination of both.

Culture plating can help confirm the presence of active, live cells, but the success rate of growing Brettanomyces in culture plates is variable.

Nonetheless, scanning wines by PCR for Brett can help winemakers isolate a general presence and risk of Brett in their wines.

Wine samples prepare for analytical evaluation. Photo by: Denise M. Gardner

Still Worried About Your Wine Post-Bottling?

Bottle sterility

Bottle sterility testing is helpful, especially when a winemaker wants to ensure wines have been bottled cleanly.  For this type of testing, it is best to sample a few bottles

  • at the beginning of a bottling run,
  • immediately before any breaks,
  • immediately after any breaks, and
  • at the end of a bottling run.

Bottles can, again, be evaluated under a microscope and evaluated for the presence of microorganisms.  Bottles can also be sent to a lab for culture plating.  The growth of yeasts or bacteria from culture plates at this stage indicates a failure of the sterile filtration system or contamination of the wine post-filtration.  Clean wines, obviously, should help put a winemaker’s mind at ease as it matures in bottle.

Ensuring a wine’s stability post-bottling is a challenge.  However, with proper cleaning and sanitation methods coupled with the right analytical records, winemakers can reduce their worry.  For information on any of these topics, please visit:

 

Advertisements

Minimizing Spoilage of Wines in Barrel

By: Denise M. Gardner

The use of oak in the winery offers many options from winemakers.  With today’s availability of various oak products (i.e., chips, staves, powders), winemakers have more choices than ever before to integrate a wood component into their product.  However, the use of oak barrels remains an intrinsic part of most winery operations.  During the aging process, oak barrels have the potential to:

  • integrate new aromas and flavors into the wine.
  • add mouthfeel and/or aromatic complexity to the wine.
  • change the wine’s style.
  • add options and variation for future wine blends.

Additionally, the barrel room is often romantically viewed upon by consumers, and it is not uncommon for visitors to find barrel show cases in many tasting rooms, private tasting rooms, or while on a guided winery tour.

The barrel room at Barboursville Vineyards (VA) gorgeously catches the eyes of their visitors. Photo by: Denise M. Gardner

 

Oak fermenters at Robert Mondavi Winery (CA) that guests can see on their famous guided tour. Photo by: Denise M. Gardner

Nonetheless, barrels also offer challenges to wineries.  One of the most inherent challenges associated with a barrel program is maintaining a sanitation program.

The growth of spoilage yeast, Brettanomyces, is often discussed amongst wineries that utilize barrel aging programs.  However, additional spoilage yeast species such as Candida and Pichia have also been associated as potential contaminants in the interior of wine barrels (Guzzon et al. 2011).  Brettanomyces, commonly abbreviated as Brett, was first isolated from the vineyard in 2006 (Renouf and Lonvaud-Funel 2007) and until that point had most commonly been associated with the use of oak in the winery.  The growth of Brett in wine has the potential to impart several aromas as a result of volatile phenol [especially 4-ethylphenol (4-EP) and 4-ethylguaiacol (4EG)] formation in the wine.  Descriptors used to describe a Bretty wine include: barnyard, horse, leather, tobacco, tar, medicinal, Band-Aid, wet dog, and smoky, amongst others.  It should be noted that the presence of these aromas does not necessarily confirm that Brett is in the wine; there are other microflora, situations (e.g., smoke taint) or oak chars that can impart some of these aromas, as well.

Brettanomyces aroma descriptors. Image by: Denise M. Gardner

When barrels are filled with wine, it’s important to monitor the wine regularly for off-flavors while it is aging.  Wines should be regularly topped up with fresh wine to avoid surface yeast or acetic acid bacteria growth that can contribute to the volatile acidity (VA).  We usually recommend topping barrels up every-other-month.  Keep in mind that free sulfur dioxide concentrations can drop quicker in a barrel compared to a tank or wine bottle (MoreFlavor 2012) and free sulfur dioxide contractions should be checked (in conjunction with the wine’s pH) and altered as necessary to avoid spoilage.  Finally, when using a wine thief, both the internal and external part of the thief need cleaned and sanitized in between its use for each and every barrel to avoid cross contamination.  Dunking and filling the thief in a small bucket filled with cold acidulated water and potassium metabisulfite (acidulated sulfur dioxide solution) is a helpful quick-rinse sanitizer.

Barrels offer a perfect environment for microflora to flourish.  Wine barrels are produced from a natural substance (wood), which has its own inherent microflora from the point of production; obviously, barrels are not a sterile environment when purchased.  However, the structure of wood is rigid and porous, which provides nooks and crevices for yeast and bacteria to harbor within.  The porosity of the wood also makes it difficult to clean and sanitize, especially when compared to cleaning and sanitation recommendations associated with other equipment like stainless steel tanks.  Guzzon et al. (2011) found that barrels used over 3 years in production had a 1-log higher yeast concentration rate retained in the barrel compared to new and unused oak barrels.  This demonstrates the ideal environment within the barrel for retaining microflora over time, even when adequate cleaning and sanitation procedures are utilized in the cellar.

Common barrel sanitizers include ozone (both gas and aqueous), steam, hot water, acidulated sulfur dioxide, and peroxyacetic acid (PAA).  A study conducted by Cornell University on wine barrels used in California wineries found the use of sulfur discs, PAA at a 200 mg/L concentration, steam (5 and 10 minute treatments) to be effective sanitation treatments for wine barrels (Lourdes Alejandra Aguilar Solis et al. 2013).  In this same study (Lourdes Alejandra Aguilar Solis et al. 2013) ozone (1 mg/L at a 5 and 10 minute treatment) was also evaluated and found effective in most barrels tested, but a few barrels that did not show adequate reduction with the ozone treatment.  While the research conducted by Cornell indicated the potential lack of cleaning the barrel thoroughly before the ozone sanitation treatment, Guzzon et al. (2011) cited ozone’s efficacy is most likely caused by its concentration.  Both are important considerations for wineries.

Barrels should always be effectively cleaned of any debris and or tartrate build up before applying a sanitation agent.  This is essential to allow for maximum efficacy during the sanitation step.  High pressure washers, a barrel cleaning nozzle, and the use of steam are some options available to wineries in terms of physically cleaning the interior of barrel.  Additionally, some wineries use sodium carbonate (soda ash) to clean some of the debris (Knox Barrels 2016, MoreFlavor 2012) in addition to the use of a high pressure wash.  Always remember to neutralize the sodium carbonate with an acidulate sulfur dioxide rinse prior to filling with wine.

Dr. Molly Kelly from Virginia Tech University has previously recommended a 3-cycle repeat of a high-pressure cold water rinse, followed by high pressure steam before re-filling a used barrel and assuming the wine that came out of that barrel was not contaminated with spoilage off-flavors (Kelly 2013).  If the barrel is hot by the end of this cycle, it may be advantageous to rinse with a cold, acidulated sulfur dioxide solution before filling the barrel with new wine.  If there isn’t wine available to refill the barrel, it can be stored wet with an acidulated sulfur dioxide solution or using sulfur discs (Kelly 2013).

It is not usually recommended to store used barrels dry for long periods of time, and wineries can use an acidulated sulfur dioxide solution (top off as if it had wine in it) for long-term storage.  However, wineries that store their barrels dry need to rehydrate the barrels prior to filling with wine.  Check the cooperage for leaks, air bubbles, and a good vacuum seal on the bung.  Steam or clean water (hot or cold, overnight) are adequate rehydrating agents (Pambianchi 2002).  Barrels that leak wine offer harboring sites for potential yeast, bacteria, and mold growth, which can all act as contaminants to the wine itself.

It should be noted that contaminated barrels (barrels that produce a wine with off-flavors) may need extra cleaning and sanitation steps to avoid future contamination when the barrel is refilled.  It is typically recommended to discard barrels that have a recorded Brett contamination.  If the barrel has picked up any other off-flavors, especially during storage, it should probably be discarded from future wine fillings.

Barrels undoubtedly offer several challenges for wineries, including proper maintenance, cleaning and sanitation.  Nonetheless, engaging in good standard operating procedures for maintaining the barrel’s cleanliness can help enhance the longevity of the barrel and minimize risk of spoilage for several wine vintages.

 

References

Guzzon, R., G. Widmann, M. Malacarne, T. Nardin, G. Nicolini, and R. Larcher. 2011. Survey of the yeast population inside wine barrels and the effects of certain techniques in preventing microbiological spoilage. Eur. Food Res. Technol. 233:285-291.

Kelly, M. 2013. Winery Sanitation. Presentation at Craft Beverages Unlimited, 2013.

Knox Barrels. 2016. Barrel Maintenance.

de Lourdes Alejandra Aguilar Solis, M., C. Gerling, and R. Worobo. 2013. Sanitation of Wine Cooperage using Five Different Treatment Methods: an In Vivo Study. Appellation Cornell. Vol. 3.

MoreFlavor. 2012. Oak Barrel Care Guide.

Pambianchi, D. 2002. Barrel Care: Techniques. WineMaker Magazine. Feb/Mar 2002 edition.

Renouf, V. and A. Lonvaud-Funnel. 2007. Development of an enrichment medium to detect Dekkera/Brettanomyces bruxellensis, a spoilage wine yeast, on the surface of grape berries. Microbiol. Res. 162(2): 154-167.

 

Brett: The Good, The Bad, and The Ugly

By: Denise M. Gardner

The age-old controversy over the existence of Brettanomyces and its impact on wine quality continues to be a hot button topic in the wine industry.  Many will argue its ability to contribute to style as part of the natural terroir associated with where the grapes were grown.  Others point to the general lack of fruit flavor in Brett-rich wines, and common negligence to winery sanitation.

The truth?

As is the case of many wine production topics, it is likely that the truth lies somewhere in the middle, but the love-hate relationship with Brettanomyces lives on.

What is Brettanomyces (aka Brett)?

Brettanomyces bruxellensis (commonly known as Brett) is a yeast commonly found in wine, which may also be referred to in the wine literature as the Dekkera species.  While believed to come from the vineyard, it was first isolated from grapes post-veraison only recently: in 2006 (Renouf and Lonvaud-Funel, 2007).  Brett is also used and found in other fermented beverages including beer, hard cider, and distilled spirits.

In the winery, the use of wood has been identified as a primary source of Brettanomyces.  In fact, many report that new oak barrels have potential to bring Brett into the winery.  This is significant to wine producers, because it was originally thought that only old, used barrels could provide contamination sources of Brett.

However, knowing that Brett can come into the winery as native microflora to the wine grapes, it is probable to assume that any winery may have Brett populations within the production area.  Therefore, it is important for wineries to determine a way to manage Brett during various stages of wine production.

What does Brett do to wine?

Brett yeast typically imparts flavor characteristics to the wine, which can commonly be described using the following descriptors, although others exist:

  • Barnyard
  • Horse
  • Leather
  • Tobacco
  • Tar
  • Medicinal
  • Band-Aid
  • Wet Dog
  • Vomit
  • Plastic or Burnt Plastic
  • Smoky

Brett Aroma

These flavor descriptors are linked to the common generation of 4-ethyl guaiacol (4-EG) and 4-ethyl phenol (4-EP).  In some cases, concentrations of isovaleric acid have also been identified and quantified.  These aromatic/flavor compounds are developed as part of Brett’s metabolism.

Additionally, many winemakers have reported a “metallic bitterness” in the finish of many Brett-infected wines (Henick-Kling et al. 2000).

Regardless of its exact descriptors, the development of Brett-like flavors often leads to a suppression of the fruit flavors, native to the wine variety.  In many cases where people consider Brettanomyces a flaw, it is due to the fact that there are no residing fruit flavors left in the wine, as Brett tends to mask and dominate the wine flavor.

How does Brett survive in wine?

Brett has the unique ability to “hang out” in the wine until an opportune moment presents itself for growth and proliferation.  Brett can survive in wines, a low pH environment, is tolerant of sulfur dioxide, and does not appear hindered by relatively high concentrations of alcohol (~14%) (Iland et al. 2007).  Additionally, Brett can utilize many substrates that Saccharomyces yeast (i.e., wine yeast) cannot: malic acid, ethanol, wood sugars, higher levels of fructose, residual amino acids and nitrogen sources.  Therefore, a wine could be considered “dry” (<1.0 g/L residual sugar) and still experience a Brett bloom at some point during its production.

One key problem with Brett is the fact that it often “surfaces” post-bottling (Coulter 2012).  Therefore, if wineries are not conducting adequate analytical and sensory testing pre-bottling, or utilizing proper sterile filtration techniques, they may be bottling a Bretty wine without knowing it!  Coulter (2012) found that it is not unusual for only some bottles within a batch of wine bottled in the same day to have Brett blooms while others do not.  Many note that Brett growth is stimulated by oxygen ingress, and Coulter concluded that the variability associated with the oxygen transfer rate of natural cork closures may contribute to post-bottling variability of Brett blooms.  However, it is important to note that the incidence of Brett growth is not isolated to wines bottled with a natural cork closure.

General Prevention of Brettanomyces in the Winery

It is difficult for wineries to manage Brett once it has surfaced in the winery.  Wineries are encouraged to avoid purchases of old barrels unless they are aware and confident in the seller’s cleaning practices.  Even well-sanitized wineries may harbor Brett populations, and should not be considered risk-free.

Maintaining adequate environmental and equipment sanitation practices is helpful to minimize Brett in the winery.  Many industry members recommend proper barrel sanitation using steam or ozone to prevent or manage Brett.

Despite a winery’s best efforts, Brett is a possibility.  In incidences when there is a Brett bloom in a barrel, it is best to isolate those barrels from others.  Avoid contaminating “clean” barrels or tanks.  Using sterile filtration prior to bottling is recommended for wines that contain Brett to prevent blooms in the bottle.

Winery cleanliness and sanitation is an important component in reducing microbial contamination risks throughout various stages of wine production.  The above image shows an example of good cleaning and sanitation practices.  Photo by: Denise M. Gardner

Winery cleanliness and sanitation is an important component in reducing microbial contamination risks throughout various stages of wine production. The above image shows an example of good cleaning and sanitation practices. Photo by: Denise M. Gardner

References Cited

Coulter, A. 2012. Post-bottling spoilage – who invited Brett? Practical Winery & Vineyard Journal.

Henick-Kling, T., C. Egli, J. Licker, C. Mitrakul, and T.E. Acree. 2000. Brettanomyces in Wine. Presented at: The Fifth International Symposium on Cool Climate Viticulture and Oenology, 16-20 January, 2000 in Melborne, Australia.

Iland, P., P. Grbin, M. Grinbergs, L. Schmidtke, and A. Soden. 2007. Microbiological analysis of grapes and wine: techniques and concepts. ISBN: 978-0-9581695

Renouf, V. and A. Lonvaud-Funnel. 2007. Development of an enrichment medium to detect Dekkera/Brettanomyces bruxellensis, a spoilage wine yeast, on the surface of grape berries. Microbiol. Res. 162(2):154-167.

Wine Quality Improvement: Defects

By: Denise M. Gardner

Wine defects happen to all of us. Sometimes I wonder if this is the humbling truth about being a winemaker. Even years of education, training and experience cannot 100% guarantee a perfect aging process after a wine has been bottled. However, a winemaker that understands why wine defects occur, how to prevent them during processing, and how to fix a problematic wine can progressively enhance wine quality more consistently than a winemaker oblivious to the potential of wine defects.

Defects and Quality – Is there a difference?

There are components of wine quality that are completely subjective. If you don’t believe me, you can read a series of comments related to a comment I shared in 2014 to the wine community about embracing both Vitis labrusca and Vitis vinifera wines for what they were to consumers and experts alike.

Wine quality may embrace both a lack of defects present in a given wine in addition to an association with a specific wine style. The stylistic component or whether or not a wine is “true to type” falls into a more subjective category.   Identification of wine defects alone is usually more direct and agreed upon wine tasters. However, I will note that some very interesting wines may also have a defect related to the wine’s flavor profile. For example, many traditional, old-style Rioja wines have associated oxidation flavors, but these wines are still found interesting, and of a particular quality, by consumers and experts. I would say the chance of having a defective wine also considered interesting is more of an “exception” compared to a “general-rule-of-thumb.”

What are common wine defects?

There are several technical wine defects, listed below, that can occur in any wine. Brettanomyces-associated off-flavors, the presence of methoxypyrazines, and flavor presence of potassium sorbate or its breakdown products are more controversial, but often noted by wine experts, critics, and writers. In general, the presence of these components may hinder the perceived quality of your wine, and winemakers should be aware of their controversial nature in the wine community.

Table 1: Summary of Wine Defects and Their Common Descriptors

Table 1: Summary of Wine Defects and Their Common Descriptors

While some defects may be measured analytically at the winery (volatile acidity in terms of acetic acid concentration and high free sulfur dioxide content), most require a winemaker to know the key aroma or taste descriptors sensorily (i.e. smell or taste). In this case, the winemaker is the last line of defense when it comes to identifying wine defects and preserving wine quality. This point emphasizes how important production education and sensory training are when it comes to crafting quality wines.

Where to Find More Information

Luckily, today’s winemakers and cellar personnel have a series of resources beyond your usual text book that are available to improve a winemaker’s ability and skill to identify and remediate defective wines.

1. Attend a wine sensory training workshop: Education is truly a tool for every winemaker. One possible workshop available in Pennsylvania includes the Wine Quality Improvement workshop, held annually in January at Penn State. During this two-day workshop, attendees will address all of the above defects: how to identify, prevent, and remediate them. Additionally, a series of hands-on activities contributes to enhancing each attendee’s identification skills that they can apply directly to their winery operation. If you act now, you may be able to register for the 2015 workshop!

Individual sensory training during the 2012 Wine Quality Improvement workshop at Penn State. Photo taken by Michael Black/Black Sun Photography.

Individual sensory training during the 2012 Wine Quality Improvement workshop at Penn State.

2. Purchase a defects aroma-identification kit: Half of the battle for becoming familiar with wine defects is through continuous exposure to standards that exude the characteristic defect aroma or by tasting wine regularly with someone experienced whom can identify the defective wines for you. This action helps improve one’s “aroma memory.” At the Wine Quality Improvement workshop, we provide each attendee with a take-home wine defects kit to encourage further practice with wine defect aromas after they leave the workshop. However, you can also purchase these kits through Wine Awakenings or Le Nez Du Vin. Additionally, Enartis Vinquiry sells a Wine Defects Kit (product #:10-309-0000) in which concentrated defect aromas can be added to an aromatically neutral base wine for aroma training.

Use of wine defects kits to enhance sensory wine defect identification sills. Photo taken by Michael Black/Black Sun Photography.

Use of wine defects kits to enhance sensory wine defect identification sills. Photo taken by Michael Black/Black Sun Photography.

3. Embrace wine criticism from a wine professional: This can be a tough pill to swallow, as the pride of one winemaker may be disliked by the taster. However, this is truly how winemakers get better at making quality wines within any style or price point. All wine styles – from native, sweet Concord wines to premium age-worthy Cabernet blends – have quality parameters and can be evaluated for defects. Find a professional that has credentials in wine sensory or tasting to discuss your wines for constructive criticism. The best professionals will also be able to direct you in terms of improving your current wines held in tanks and future wines that you will produce. You can also contact your local Extension Enologist for guidance on tastings.

Use feedback on your wines to your advantage. Photo taken by Michael Black/Black Sun Photography.

Use feedback on your wines to your advantage. Photo taken by Michael Black/Black Sun Photography.

4. Contract a wine lab to improve your wines: This thought follows #3, as it is similar in theory. Some wine labs (like Enartis Vinquiry or Virginia Tech’s Enology Service Lab) may offer sensory feedback for a fee. This advice can be helpful, as many of these labs have a panel of individuals taste and evaluate the wine. As tasting abilities vary, having more than one person taste a wine for defect identification can be valuable. (Having multiple people available to taste wine as it goes through production should also be considered in cellar.)

5. Work with winery consultants: Your winery consultant may also be your “wine professional” that identifies problematic wines. That’s okay! While winery consultants come at a fee, the value of winery consultants is that they can improve your production practice to meet your needs while also educating your employees (or yourself) on a one-on-one basis. Luckily, each consultant is unique, and finding one that fits the mentality of your production can put your winery on a successful path for years (or generations) to come.

Alain Razungles, Professor of Enology at the Institute des Hautes Etudes de la Vigne et du Vin. Here he is tasting some eastern U.S. wines and providing feedback to the winemakers in the audience.

Alain Razungles, Professor of Enology at the Institute des Hautes Etudes de la Vigne et du Vin. Here he is tasting some eastern U.S. wines and providing feedback to the winemakers in the audience.

6. Attend defect-based seminars at wine conferences: Many of the local and national wine conferences offer talks on wine defects or other quality issues. The Eastern Winery Exposition, Wineries Unlimited, B.E.V.-NY Conference, PA Winery Association Conference and PA Wine Marketing & Research Board Symposium, and American Society for Enology and Viticulture (ASEV)-Eastern Section Annual Conference are all local options for Pennsylvania producers to attend.

Attending wine conferences and workshops can enhance your wine education. Photo by Michael Black/Black Sun Photography.

Attending wine conferences and workshops can enhance your wine education. Photo by Michael Black/Black Sun Photography.

7. Online guides: Don’t forget to keep reading. Both Penn State and Cornell offer free online publications that can be helpful for beginner and expert winemakers. Penn State’s emerging “Wine Made Easy” fact sheet series has already covered sulfur dioxide and hydrogen sulfide Cornell’s “Cellar Dweller” and enology newsletters also offer a plethora of information pertinent to today’s winemakers.