By: Denise M. Gardner
While in the midst of harvest (and all the craziness that comes with it), I thought I’d take a week to remind people about proper cleaning techniques, improving sanitation, and why these two operations are essential for wineries.
I know many of you are ready to close this page now, but WAIT!
I have heard many excuses for short cutting on cleaning over the years. Do any of the following sound familiar?
- There is not enough time in the day to properly sanitize.
- There are not enough employees to do all the work to properly clean.
- Cleaning would take all night to complete properly.
- It’s not necessary to clean/sanitize with wine.
- The wine will sell anyway.
- Cleaning and sanitizing does not actually improve wine quality.
- Sanitation is not really important.
- Proper cleaning does not increase the price in which the wine can be sold.
If you or any of your employees have used at least one of these statements in the past, you could be suffering from poor cleaning and sanitation practices!
In all seriousness, having good cleaning and sanitation procedures can actually save the winery time and money in the long run.
In the height of harvest, I’m sure this is a tough sell. But let’s consider some of these practical cleaning and sanitation suggestions for small, commercial wineries.
On the same page with cleaning vs. sanitizing
Let’s start with a review of definitions, as it can get very confusing. Below are some general definitions taken from a series of sources (Fugelsang and Edwards 2007, Iland et al. 2007, Iland et al. 2012, Solis et al. 2013) to explain the differences between cleaning, sanitation, and sterilization.
- Cleaning – the physical removal of dirt, debris or unwanted material (solid or liquid) from a surface
- Sanitizing – a 99.9% (3 log) reduction of microorganisms
- Sterilizing – the complete removal or inactivation of microorganisms
The wine industry is primarily focused on cleaning and sanitation protocols, as there are not many sterile practices utilized in winery operations (unless you are one of the lucky few wineries bottling aseptically). Even if processors are using sterile filtration to remove yeast and bacteria from the wine, once the wine exits the filter, it comes in contact with equipment that is only sanitized (hopefully!).
Additionally, wine bottles or packages are not sterile when being filled. Even new bottles can contain yeast or bacteria that can potentially contaminate a finished wine. Hopefully, proper sulfur dioxide levels should keep this microorganisms at bay.
For all of these reasons, as the wine has the opportunity to come in contact with existing microflora on processing equipment, wine is bottled in a sanitized environment.
Remember proper sanitation is primarily having good cleaning protocols. Cleaning should always precede sanitation. Failure to physically remove all of the debris from equipment, results in an inability to properly conduct sanitation procedures.
There are several different detergents (cleaners) and sanitizers that wineries can use effectively. Example sanitizers include quarternary ammonium compounds (QUATS), peroxyacetic acid, chlorine dioxide, hot water, and steam. Additionally, wineries can find use in an acidulated (citric acid) sulfur dioxide mixture. However, all sanitizers should be selected specifically for the job at hand (Iland et al., 2012) with consideration towards the microbes that one is trying to avoid.
Most commercial wineries can really focus on improving cleaning practices to provide a step in the right direction towards improving quality and sanitation practices inside the winery.
If you think you may need some help in obtaining winery sanitation basics, please refer to this Northern Grapes Webinar by Randy Worobo on YouTube. Or check out this PodCast by Hans Walter-Peterson and Chris Gerling from Cornell: Winery Sanitation Presspad Podcast, which focuses on preparation for harvest and including sanitation in that prep.
Cleaning harvesting equipment
While this is usually one of the places winemakers feel most complacent about, I would argue that this can be one of the most important places to take care in your cleaning and sanitation practices.
- There is a lot of effort that goes into the growing season in order to adequately ripen wine grapes for many sensory nuances. Additionally, the vineyard is the source of many microorganisms that enter the crush pad and cellar. [For those that use mechanical harvesters, do not forget cleaning and sanitation of this vital piece of equipment (Pregler 2011).] Giving the grapes a clean surface to encounter upon entering the winery ensures that all of that hard work is truly appreciated and preserved from the start of fermentation.
- Without proper cleaning and sanitation practices, you are likely increasing the microbial populations of your wine before it even gets a chance to ferment. Think about it. After crushing/destemming a lot of rotting Pinot Grigio, Pinot Noir, or botrysized Riesling, how many people spray down the equipment (lightly) and move onto crushing the next lot of fruit even if the second lot is cleaner than the first? Sometimes, the order of grape crushing cannot be avoided. But how it is handled upon receiving can be altered. If this is the case for your winery, and you are avoiding good cleaning and sanitation steps in between lots of fruit, you are cross contaminating your juice with, not only yeast and bacteria present in the rotted fruit, but also residual enzymes, proteins, and other by products that can alter wine chemistry in the clean fruit that follows. Think about the potential production problems this can cause later on down the road: laccase browning, acetic acid development, off-flavor development, etc. If such problems arise, it can cause labor and financial investment at a later time.
- Residual foodstuffs (e.g., old grape skins, rice hulls, pulp) can contribute to off flavors within the finished wine. Recent research has shown that there is potential for aromatically-intense varieties (i.e., Niagara, Concord, or Noiret) to leach their flavor compounds into more neutral varieties through absorption and diffusion of equipment-based plastic components that come in contact with the juice and wine (Smith 2014). It is also possible for alien material (i.e., green matter, old rice hulls, and stuck fruit) to contribute to flavors in the final product that may be undesirable or challenging to fix.
- Remember that rice hulls are a pressing aid primarily used for A) hard-to-press varieties to increase yield or B) bulk operations in which pressing time is of the essence. Previous studies, such as the one found here, have shown a detriment in flavor and quality of wines pressed with rice hulls for certain varieties. Additionally, rice hulls can be difficult to remove from the wine press and create potential microbial infection sites for later grapes/juice/wine. It is recommended that the use of rice hulls be on aromatically intense or difficult-to-press varieties (e.g., many native varieties). Use of rice hulls in grapes that have a lot of rot will not only help increase yield of the fruit, but also increase extraction and retention of rot byproducts, which can contribute to off-flavor development.
- Proper cleaning can help maintain your equipment longer. Over time, plant material can slowly degrade equipment. Doing a little scrubbing and properly sanitizing repeatedly can help keep your equipment in relatively good condition. Additionally, the longer debris is left on equipment, the harder it is to remove.
Properly maintaining harvest equipment also leads a good example for all of the other equipment in the winery.
Tanks, Barrels and Bottles
These are places in the cellar where it can get easy to take short cuts as opposed to properly cleaning or sanitizing equipment.
These are places in the cellar where it can get easy to take short cuts as opposed to properly cleaning or sanitizing equipment.
- Remember that tartrate build up in tanks and barrels can make it difficult to properly sanitize the covered portion of the tank/barrel. Make sure to first dissolve large tartrate deposits with hot water before going through a cleaning and sanitation cycle. Without dissolving tartrates, the equipment is not going to get properly cleaned or sanitized.
- When getting ready to fill a tank, remember to run a sanitizer through the tank first to minimize microbial populations on the interior surfaces that come in contact with the wine. This helps ensure varietal flavor nuance and minimizes the risk for spoilage. [Note: Some sanitizers are no-rinse sanitizers and do not require a rinse after the sanitation chemical is applied. Other sanitizers may require a rinse following application. Always check the directions pertaining to your sanitizer carefully before use to ensure it is being used properly for best efficacy, and always use proper protective clothing when handling sanitizer agents.]
- Minimize harboring sites for insects and microbes within the cellar are a practice that can be done at the end of every shift. During harvest, one big problem I see is dripping, dried juice or wine on the exterior of tanks or fermentation bins. While this doesn’t seem like a big deal, it’s an attractive site for fruit flies, which also makes them attractive deposits for spoilage yeast and bacteria. The objective of removing these places of dried juice/wine is to minimize insect infestation in the winery and avoid potential contamination of clean wines.
- Barrels need cleaned prior to sanitation regimes like other pieces of equipment. Many barrel cleaning systems are automatic and can be an efficient way to clean the interior of barrels.
- Barrels are porous and have a lot of grooves inside of them, which can make it difficult to properly clean and sanitize. It is important to note that due to the nature of the barrel, it cannot be sanitized in a way that a stainless steel tank can be sanitized. However, there are many different cleaning and sanitation options for barrels out there, some of which are explored in this Appellation Cornell newsletter from 2013. This study evaluated natural barrel microflora (yeast, including Zygosaccharomyces and Brettanomyces) before and after a sanitation regime was conducted.
- Sulfur wicks are a good way to treat the interior surface of the barrel, but this practice does not penetrate into the interior of the wooden staves (Iland et al. 2007). Also, ensure that the wick is not submerged below any left over water at the bottom of the barrel, as it may extinguish the wick (Iland et al. 2007). Make sure the bung is tightly sealed for best efficacy of a sulfur wick (Rieger 2015).
- Bottling lines are not immune to cleaning. In the food industry, it is commonly noted that most contamination comes from the environment in which the food is processed. This can happen in wine processing, as well. Dust on the bottling line can harbor yeast and bacteria that can be disturbed or moved into the air during large movements, like when bottling a finished wine. Keeping the bottling line clean is a good way to help minimize contamination during bottling operations.
Small Steps That a Commercial Winery Can Take to Improve Cleaning and Sanitation
Being a smaller or boutique sized winery can definitely have its advantages in the cleaning and sanitation world. It’s easy to get creative in terms of improving efficiency, use of, and efficacy of cleaning and sanitation practices. Below are some practical solutions for wineries struggling to incorporate cleaning and sanitation practices in the winery.
Use brushes, like Perfex brushes, to properly scrub equipment during cleaning operations. These are especially helpful when getting that pesky debris off of processing equipment.
Color code brushes or cleaning materials to emphasize their use and make it easier on your employees. By keeping the necessary supplies handy and easy to use, efficiency is likely to improve, which can actually help improve the quality of cleaning operations. Typically, white brushes are reserved for food-contact surfaces (the part of the equipment that actually comes in touch with food) during sanitation steps. Yellow brushes can be used for environmental cleaning (non-food-contact surfaces like the exterior of tanks). Other colors can be purchased for additional specific purposes: detergent only, sanitizer only, etc. Keep the brushes handy during all processing operations.
There is a great article from Food Engineering on the power of color coordination in the food industry, which you can read here.
Consider keeping your cleaning and sanitation system on wheels. While in Oregon, I found it clever how larger wineries kept their fittings on mobile units to aid in availability, cleaning, and organization (Figure 3). While this concept may be helpful to some wineries, I think it can also be applied to cleaning materials. Keeping cleaning materials isolated to a mobile until allows for quick use and organization throughout the entire production facility and minimizes needless travel time to walk back and forth towards where supplies may be kept. Examples, below, for how to improve mobility of your cleaning supplies are given in Figure 4.
You do not need to use fancy (or expensive!) cleaners or sanitizers all of the time in the winery. For quick clean ups, use warm water mixed with potassium carbonate to get stuck or sticky material off of equipment. Use with caution as it can get slippery!
Follow a potassium carbonate rinse with a warm water rinse to remove the solution from equipment and environmental surfaces.
Acidulated sulfur dioxide (Figure 5) can act as a quick sanitizer as well, and is easy to make up and use in the winery. Plus, citric acid, sulfur dioxide, and water are found in wine and will not have an effect on wine quality or flavor.
Finally, I always recommend wineries keep a supply of 70% ethanol in a spray bottle handy for quick cleaning solutions. Ethanol can be used to clean up small spills, quickly rinse sampling valves before and after sampling, or act as an exterior sanitizer towards things like wine thieves, sampling pipettes, and lab benches where one is running analysis. This is an easy chemical to keep on a mobile cart or scattered throughout the winery. However, be sure to purchase food grade ethanol from a chemical supplier and dilute down to ~70% with non-chlorinated water.
Cleaning up at the end of a processing day makes the start up for the next processing day a lot easier. If the equipment is clean to start, then all you have to do is run a quick sanitizer through the equipment before the start of processing operations.
Use hot water to rinse your equipment and make sure your hose has good pressure. Cold water is definitely energy efficient, however, hot water can help remove a lot of debris quicker and make any potential scrubbing easier. Be cautious of the metal on equipment heating up with use of hot water. Also, increasing hose pressure can help dislodge any debris from equipment, which can save time during cleaning operations.
On large processing days (those days when 3 or 4 varieties are being crushed at the winery), designate the day to processing and wait until the next day to complete other operations that can be delayed. Now, some flexibility needs to be made for things like punch downs or pump overs. However, teamwork is key: punch down time can be reduced if there is more than one punch down tool available for employees to use. Juice analysis (pH, TA, Brix, and YAN) is time sensitive, because if the juice starts going through spontaneous fermentation, the results of these chemical indices will change. However, obtaining all of the juice samples from all lots of incoming fruit before starting analysis can save your employees time and avoid splitting up duties during a processing day. With 3 employees, one person could run analyses while the remaining 2 finish cleaning up at the end of a processing day. Reserve racking or moving wines for days when a little less is going on in the cellar unless it is absolutely necessary to open up space in tanks for incoming fruit.
Minimize barrel-to-barrel or tank-to-tank contamination by having small sanitation vessels/buckets (filled with sanitizer) handy and isolated for cleaning/sanitation use. Use a bucket filled with acidulated sulfur dioxide solution to submerge (and fill) your wine thief in prior and after each barrel sample. For smaller samples, consider using one-time-use or disposable pipettes (Figure 6). If you have a 70% ethanol solution in a spray bottle, the metal fittings at the end of hoses can be quickly sprayed in between barrels when transferring barreled wine into a tank or transferring wine from a tank into barrels to help minimize cross contamination (Illand et al. 2007).
Check to see how clean your equipment is with quick testing strips like Pro-Clean Protein Residual testing strip by Hygiena. These testing strips are a good indicator on how well your cellar crew is cleaning equipment. The problem with protein test strips, like the one shown, is that it will detect all organic matter (Iland et al., 2007). It does not represent live or viable microorganisms; there are rapid tests available that may be more representative of microorganism populations.
The video below indicates the ease in which these are to use:
Other options include luminometers like Hygiena’s SystemSURE Plus or 3M Clean-Trace (Rieger 2015), which are also non-specific, but can indicate the cleanliness of a contact surface that is swabbed properly.
While cleaning and sanitation may seem arduous, most wine quality problems I encounter – including funky off-flavors that are challenging to identify, presence of VA, large quantities of wine affected by cork taint, and lack of varietal character – could be primarily avoided with more routine and better cleaning operations. Improving cleaning and sanitation operations can be a step in the right direction for wineries to improve quality associated with their business.
Iland, P., N. Bruer, A. Ewart, A. Markides, and J. Sitters. 2012. Monitoring the winemaking process from grapes to wine: techniques and concepts. 2nd Ed. Patrick Iland Wine Promotions Pty Ltd. Campbelltown, Australia. ISBN: 978-0-9581605-6-8.
Iland, P., P. Grbin, M. Grinbergs, L. Schmidtke, and A. Soden. 2007. Microbiological analysis of grapes and wine: techniques and concepts. Patrick Iland Wine Promotions Pty Ltd. Campbelltown, Australia. ISBN: 978-0-9581605-3-7.
Pregler, B. Nov 2011. Industry Roundtable: Cellar Sanitation. Wine Business Monthly.
Rieger, T. Oct 2015. Microbial Monitoring and Winery Sanitation Practices for Quality Control. Wine Business Monthly.
Smith, JC. 2014. Investigating the Inadvertent Transfer of Vitis labrusca Associated Odors to Vitis vinifera Wines. Retrieved from Electronic Theses and Dissertations for Graduate School: Penn State: https://etda.libraries.psu.edu/catalog/23501.
Solis, M.L.A.A., C. Gerling, and R. Worobo. 2013. Sanitation of Wine Cooperage using Five Different Treatment Methods: an In Vivo Study. Appellation Cornell. 2013-3.
By: Denise M. Gardner
Well, the time is here – harvest season! And if you haven’t geared up already, it is now crunch time.
In my travels across the state, I am seeing a lot of good things in the vineyard, which makes me eager for the 2016 crop to come into the winery where it can be made into wine. While the drought has impacted a large portion of the state, I’m also seeing good color, tannin, and flavor development in fruit, and am hoping for a nice 2016 vintage. This picture of ripening Pinot Grigio from the Endless Mountains region shows just how far along the fruit is coming into its developed stage.
With all that work that went into a good growing season, please don’t forget that harvest is also about taking the care and time required to make a clean, quality wine. Otherwise, all of that hard work in the vineyard may be lost in the wine! While taking a few short cuts here-and-there can be appealing during the busy harvest season, some short cuts can detrimentally impact final wine quality or even lead to flaws when things like cleaning and sanitation steps are forgotten or minimally implemented in the cellar.
The following blog post will review a few practical steps that winemakers and the cellar crew can take now in order to prepare for the first lot of incoming fruit in an effort to try to minimize stress and chaos during a hectic time of year.
1. Order your harvest materials
While “free shipping” July has passed, if you haven’t ordered your harvest supplies yet, now is the time to do it. Take a few hours and figure out what you will need to get through harvest. This includes anything from sugar and acid to yeast and malolactic bacteria. Don’t forget your sanitizers. There is a PSU Wine Made Easy Fact Sheet that gives a more thorough list of supplies you should make sure to have in the winery and properly stored for use prior to the start of harvest.
2. Get last year’s wines bottled
It goes without saying that getting last year’s inventory moved into bottles will free up tank, barrel and storage space for this year’s incoming fruit. It makes for a much easier transition if all of your wines that need bottling are bottled before harvest season starts. Bottling during harvest is not only chaotic, but it will tire your employees (and you!) and may lead to harvest decisions that may be regretted later.
Always make sure to get your bottled wines properly stored and away from any “wet areas” on the production floor. If possible, bottled wines should have a separated storage area with an ideal storage environment that is physically separated from production. From there, stored wines can be moved into retail space when needed.
3. Check and prepare equipment
Many wineries experience equipment failures during harvest as most of the equipment has been left in storage throughout the winter, spring and summer months and was not routinely used. This lack of use can be wearing on equipment and may lead to equipment failures during production.
Therefore, we recommend pulling out your crusher/destemmer and press to get it up and running before the first grapes arrive. As the equipment is probably dirty, give it a good physical cleaning and sanitation regime to ensure that it is in its best condition before grapes come anywhere near it. I have seen many presses with left over rice hulls inside of them, and cellar staff should be reminded that left over debris are potential contamination sources for microbial spoilage. Additionally, old debris may alter the flavor for this year’s wines, which would minimize the efforts that were taken in the vineyard to mature fruit. To make fresh, clean wines, cleaning and sanitation is quite important.
It is imperative to pull out all of your pumps and ensure that they are actually working before those first grapes arrive. Pull down hoses and ensure they are all properly cleaned. Give the hoses an inspection, clean and re-dry before their first use.
While it is busy work, and it may be tedious, having clean and working equipment is a life saver during the actual harvest period.
4. Double check you have plenty of analytical supplies to get you through harvest
For those that have analytical labs, make sure that your labs are properly stocked with hydrometers, Clinitests, refractometers, pipettes, glassware, pH probes, and all of the associated chemicals that you will need during harvest season. This way, everything is ready to go when you need it.
Get your spreadsheets or data collecting systems prepared prior to when the grapes arrive so that you can easily input data throughout harvest season when you are crunched for time.
5. Timing is everything
If you are like many winemakers in Pennsylvania, you may be making several Pennsylvania-grown fruit wines. Remember that several other fruits can be cold-stored (e.g., apples) or frozen (e.g., strawberries, blueberries, raspberries) until after the grape harvest is completed. When the grape fermentations start to slow down, you can remove the stored fruit for processing and fermentation. This allows you to focus on your grape wines first and then alter your focus to the fruit wines after the busy season associated with the grape harvest has passed.
On a positive side, freezing the other fruits helps to concentrate their flavors and will provide a fruitier base for fermentation.
6. Consider your resources
Remember that Penn State Extension is available to answer questions you may encounter during the harvest season. It is always easier to prevent problems as opposed to fixing them in the wine, so please do not hesitate to use this resource.
Additionally, we have a full 2-page fact sheet and check list for considerations prior to harvest that may be helpful to many winemakers: http://extension.psu.edu/food/enology/wine-production/wine-made-easy-fact-sheets/preparation-for-harvest
When in a pinch, remember that there are calculators online to help you make product additions or alterations:
By: Denise M. Gardner
Home winemaking and home brewing can be some fun hobbies for enthusiasts or amateur growers and winemakers. However, most home winemakers experience the same set of problems year after year without practical solutions for how to fix their wines or avoid challenges during production. The following blog post discusses some possible considerations when making wine at home.
Concentrate – Grapes – or Juice
One thing to note is that concentrates are produced and manufactured with a pretty high success rate that the fermentation will complete with some sort of noticeable quality resembling wine. These end up being the best product to use as an introductory fermentation base for those just starting to learn about the winemaking process. The concentrate is simple: pour into the fermentation vessel and “just add water and yeast.”
The problem with concentrates is that they are easily identifiable, meaning the finished wines have a specific taste and quality standard that is noticeable sensorially regardless of the variety or source of the concentrate. These wines will likely appear “simple” with nuanced fruit characteristics and a strong perception of alcohol.
However, when home winemakers switch to purchasing bulk juice or grapes, many new fermentation problems can arise that they did not experience during their use with concentrates.
This is due to the fact that bulk juices (purchased from a broker or home winemaking supply store) may contain preservatives (i.e., sulfur dioxide) that can make the initiation of fermentation more challenging. Additionally, juice and grape quality is dependent on the source and how long the material was in storage before it arrives to the home winemaker’s fermentation vessel.
With juice and grapes, you are also dealing with the native microflora (e.g., yeast and bacteria), some of which can also be spoilage microorganisms, which can have numerous effects on fermentation kinetics and the finished wine quality.
However, using grapes or bulk juice as the starting base will provide a finished product that is more representative of where the grapes were grown (i.e., terroir representation) and provide the winemaker with more options for making the product unique.
Basic sanitation is what many home winemakers struggle with the most during fermentation and wine storage.
While most commercial sanitizers are not available to home winemakers, basic cleaning and sanitizing principles can easily be applied to home winemaking practices.
First, always make sure equipment is pulled apart and fully cleaned with hot water, a small (very small!) amount of non-scented dish soap, and some good, old fashioned elbow grease. Removing debris and build up from all of the processing equipment improves the efficacy of a sanitizer. Cleaning is at least 95% of sanitation, and this theory is true in home winemaking as well.
After the equipment is properly cleaned and rinsed with hot water, sanitation can follow. Using a citric acid – sulfur dioxide blend in cold water is a good no-rinse sanitizer that home winemakers can utilize. However, it is important that home winemakers take the care and precaution to ensure safety associated with using volatile sulfur dioxide. Volatile sulfur dioxide is a lung irritant and can cause serious health issues if used improperly. People with asthma or other lung-related conditions should not come in contact with potassium metabisulfite or sulfur dioxide. For more information pertaining to how to properly use sulfur dioxide, please refer to Penn State’s Wine Made Easy Fact Sheet and your potassium metabisulfite supplier.
The citric acid – sulfur dioxide sanitizer is a no-rinse sanitizer. This means that after the equipment has been sanitized, the juice or wine can come in contact with the equipment without any worry by the home winemaker. Both citric acid and sulfur dioxide are naturally found in wine, so its use should not alter the flavor of the wine in any way.
Use Nutrients during Fermentation
Many home winemakers use non-specific yeast nutrients during fermentation. However, the research and commercial industry worlds, we have started to learn that nutrient additions need to be specific towards the fermentation. Look to see if you can find commercial suppliers of yeast nutrient from companies like Beverage Supply Group, Christian Hansen, Enartis, Laffort, or Lallemand (to name a few of the suppliers). Some home winemaking supply stores will carry small quantities of these products, and they are worth the purchase.
At minimum, using a yeast hydration nutrient (like GoFerm or an equivalent) will help to start the fermentation positively. Complex nutrients (like Fermaid K or an equivalent) are typically recommended (up to a certain point) before using DAP.
If you can find a way to measure yeast assimilable nitrogen, or YAN, then nutrient additions can be made in specific quantities, using specific products (i.e., hydration nutrients, complex nutrients, or DAP) at the start and 1/3-of-the-way-through fermentation. Utilizing the supplier’s guidelines for the rates of additions of your products, based on the starting YAN concentration, is a good way to minimize the risk of the wine tasting like rotten eggs or canned vegetables.
Manage Oxygen Exposure
Winemaking is tedious. It requires the winemaker to constantly check and monitor the wine to ensure that things have not gone awry.
Home winemakers should try their best to minimize long-term oxygen exposure. Using vessels to minimize surface area at the wine-oxygen interface will help reduce the risk of acetic acid bacteria contamination and growth, which contribute to the volatile acidity (i.e., the acetic acid – or vinegar – and nail polish flavors) of a wine.
If you need to “top up” carboys, use sanitized marbles to “push” the volume of the wine up into the neck of the carboy. This helps minimize the surface area at the oxygen interface.
Avoid letting the wine “sit” without an active primary fermentation or malolactic fermentation (MLF). Make sure when both of these fermentations are complete, properly treat the wine with potassium metabisulfite to ensure preservation and stability.
Keeping the wines stored in a cool location will help minimize bacterial growth or yeast spoilage, while preserving the wine.
Bottling the wines as soon as you can post-production can help ensure quality and stability.
Avoid Making Wines in Aromatic Environments
One problem that some home winemakers face is aromatic absorption associated with the odor of the environment in which the wine was produced. This tends to be a problem when wines are made in an unfinished basement.
Wines are alcoholic solutions, which can absorb surrounding odors. As unfinished basements tend to have that “wet basement” odor, the wine will likely absorb that aroma and flavor into the finished product. However, many people may not be aware of the flavor until after the wine is removed from the odorous environment.
These are just a few solutions pertaining to home winemaking situations. However, you can find more resources, including “how to” book recommendations on the Penn State Extension Enology website.
Need more help in learning how to identify wine problems? Check out some of Penn State’s local workshops pertaining to wine defect identification. The next workshop is coming up on June 9th, 2016!
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.
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:
- Wet Dog
- Plastic or Burnt Plastic
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.
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.
By: Denise M. Gardner
It’s bottling season! Wineries are gearing up for the current growing season and another harvest. Now is the crunch time to get everything from last year’s vintage out of tank and barrel, and into bottle. Bottling is time intensive and tedious for a winery of any size, and it’s easy to leave the bottling line with contaminated wine bottles.
In fact, previous research has shown that even when sterile filtration steps are properly performed, over between 39-58% of the bottles leaving the bottling line end up with yeast in the bottle (Neradt 1982). Renouf et al. (2007) found that using sterile filtration (0.45 micron absolute filter or lower) was the only way to eliminate most microorganisms from the wine during bottling. However, in bottles that contained microbial populations upon bottling, Brettanomyces was able to bloom in the bottle after 6 months of storage, and increase 4-EP and 4-EG volatile phenol concentrations within 10 months post-bottling (Renouf et al. 2007). In fact, long term storage of red wines infected with Brettanomyces found this spoilage yeast became the dominate microbial population in the bottle, outcompeting most other microorganisms (Renouf et al. 2007). Yikes!
Bottling is one of the most important steps to retain wine quality at the winery. Therefore, this blog post will focus on a number of bottling considerations for wineries:
- Make pre-bottling additions before bottling day
Most product additions, including sulfur dioxide, potassium sorbate, gums, sugar, etc. require at least 24 hours of stabilization in wine before it can be sterile filtered and bottled. There are some exceptions, and some products may require longer stabilization time or need to be added during bottling, after filtration. You should rely on the advice of your product supplier when working with new additives. Additionally, some filter suppliers recommend making large sugar additions to wine at least a week before filtration.
If you are making the final sulfur dioxide addition the day before bottling, make sure you measure the concentration of free sulfur dioxide in the tank prior to bottling. Take multiple samples throughout the tank to ensure that the sulfur dioxide has penetrated all sections of the wine. If the sulfur dioxide is not high enough to reach the 0.85 ppm molecular level, it is best to alter additions and wait to bottle another day. For more information on sulfur dioxide additions at various wine pH’s, please click here.
Whether you have a manual bottling and capping system, or a high-tech bottling line, physically cleaning the bottling line is essential to maintaining proper hygiene in the winery. Bottling is one of the key areas where the quality of the product can greatly be degraded. Have brushes specific for the bottling line, and utilize detergents that break down wine debris or environmental dust.
Some bottling lines will require personnel to remove valves, hose lines, etc. to physically clean off debris or biofilms. Following cleaning operations, proper sanitation is essential to reduce microbial contamination through the bottling process.
*Note: The use of potassium sorbate will not inhibit contamination of your wine through bottling. Only proper sanitation techniques can reduce microbial populations and minimize risk of microbial spoilage in the bottle.
- …and Sanitation of the Bottling Line
As mentioned above, proper sanitation reduces microbial populations within food equipment and the surrounding environment, in order to reduce the risk of potential contamination within the packaged product – in this case, wine. While greatly underestimated, the surrounding environment is a potential contamination point in wineries, especially during bottling. Aseptic bottling operations are not necessary to maintain good hygiene, but it is often recommended that the bottling line be isolated within the winery to avoid large air movements while wine is packaged. This helps to avoid yeast, which are ubiquitous, contamination during the bottling process.
Floors, walls, and drains should be easily accessible and cleaned in the bottling area to help reduce environmental contamination. Routine environmental sanitation will also help reduce the risk of contamination.
Additional primary sources of contamination on the bottling line have previously been identified by Neradt (1982):
- Filler/Fill spouts
- Bottle sanitizer
- Bottle mouth
Proper sanitation of the bottling line first requires proper cleaning to remove all physical dirt and debris. Otherwise, the sanitation step is literally “cleaning dirt.”
Water chemistry, temperature, and contact time all affect the efficacy of sanitation. The use of soft water is often recommended for sanitation to avoid hard water residues that can harbor microbial populations.
The minimal temperature-time combination to sanitize equipment using hot water is 180°F (82°C) for at least 20 minutes. This temperature must be obtained at the coldest point in the bottling line. For bottling operations, this will be where water leaves the system. Butzke (2010) notes: “…that humans perceive water as painfully hot at temperatures just above 42°C (108°F).” Therefore, temperature readings should be taken with a calibrated, food-grade thermometer.
Individuals should take caution when working with scalding material or any chemical agent during the sanitation step. Always remember to ensure that employees have proper safety equipment and adequate ventilation.
Note that if you are using hot water, heat, or steam to sanitize the bottling line, you will need to bring the equipment back to the temperature of the wine to avoid cooking the first few gallons of wine that flow through the bottling line. Do not use tap water to change the temperature, as this will ruin the purpose of the sanitation step. Some wineries prefer to lose the first few gallons of wine, while others will follow a heat step with cold acidulated-sulfur dioxide mix.
Fill heads are an easy source of potential contamination. Periodically throughout bottling (i.e., every hour, or every time that breaks are taken), these can be sprayed or misted with 70% food-grade ethanol to ensure proper sanitation. Allow the ethanol to evaporate before proceeding. Wineries could also dip the ends in a properly made acidulated-sulfur dioxide mix. Do not wash off sanitized equipment with a towel or “clean” paper towel.
Always remember that the efficacy of cleaning and sanitation is dependent on the processor to complete this task correctly. Both cleaning and sanitation should take place immediately before bottling and immediately after bottling is completed. For more information on proper sanitation techniques, wineries can attend the Penn State Food Safety and Sanitation Short Course, which emphasizes key concepts related to sanitation processes. This course is also available in online content.
Additionally, the book, Winemaking Problems Solved, has an entire chapter designated to trouble shooting during bottling operations, and is recommended for any winery.
- Checking sterile filtration integrity
Filter integrity is an easy step that wineries can take to ensure their sterile filtration unit is working properly. Remember that sterile filtration requires the use of a 0.45 micron (or smaller) absolute filter cartridge. The Bubble Point Test is an integrity test that should be applied to a filter before and after bottling to ensure filter integrity.
- Bottle washing
While bottles are sterile when they are formed, many retain cardboard dust (“case dust”) in the bottles by the time they reach the bottling line in the winery, and this acts as a contamination point. Wineries should also be aware of tiny glass shards that may be retained within the bottle during glass manufacturing.
The best way to remove dust and debris in the bottle is by gas jetting: injecting a small stream of inert gas (e.g. nitrogen) prior to the bottle’s use.
As this is not a sanitation step, it is recommended that bottles also undergo a pre-rinse step with an approved no-rinse sanitizer. Many wineries utilize an acidulated-sulfur dioxide rinse or ozonated water.
- Inspecting filled bottles
Many wine microbiology text books recommend sampling one or two filled wine bottles every hour during bottling. There are several things that wineries can look for including using a microscope to scan for potential contamination, using membrane filtration to enumerate yeast and bacteria on a Petri Dish (pg. 236-238 in Wine Microbiology), or sending samples away to test for bottle sterility. This quality control step can help minimize worry post-bottling and provide ample feedback regarding bottle efficacy.
- Checking sulfur dioxide depletion
The use of sulfur dioxide is the last line of defense in terms of microbial stabilization while wine is in bottle. Many refermentation incidents are a result of too little free sulfur dioxide in the bottle.
During bottling, the wine will lose a little bit of the free sulfur dioxide concentration. Typically, this is around 10 ppm of free sulfur dioxide concentration, but it will vary from winery to winery, and bottling line to bottling line. Wineries should sample the sulfur dioxide concentration about 24 hours post bottling to evaluate the average loss of sulfur dioxide during the bottling process. Extra additions of sulfur dioxide can be made before bottling to compensate for the loss during the bottling process.
Resources & Literature Cited
Butzke, C. “How long do I need to disinfect my bottling line if my hot water is less than 82°C (180°F)?” in Winemaking Problems Solved
Neradt, F. 1982. Sources of reinfections during cold-sterile bottling of wine. Am. J. Enol. Vitic. 33(3):140-144.
Renouf, V., M.-C. Perello, G. de Revel, and A. Lonvaud-Funel. 2007. Survival of wine microorganisms in the bottle during storage. Am. J. Enol. Vitic. 58(3):379-386.