Please note that the LAFFORT webinar “Protecting Quality in a Challenging Harvest” has been changed from July 8th to July 22nd. Please see the attached pdf for more information and to register. If you registered for the July 8th webinar, you will need to register again.
by Molly Kelly, Enology Extension Educator
The virus that causes the Coronavirus 2019 Disease (COVID-19) is known as SARS-CoV-2. The virus can be easily transmitted, especially in settings where large groups gather. Penn State Extension offers the guidelines of health and safety best practices related to the reopening of tasting rooms to mitigate the spread of the virus. A series of general best practices was summarized through guidance from federal and state agencies including the Centers for Disease Control (CDC), US Department of Labor, American Industrial Hygiene Association (AIHA), Occupational Safety and Health Administration (OSHA), Food and Drug Administration (FDA) and the Pennsylvania Department of Health.
In this series of blog posts, we will first examine Pennsylvania-specific guidelines. Future posts will focus on federal guidelines. We will offer the most up-to-date information but please realize that guidelines may change quickly. In this post we offer some links that would be useful to check on a regular basis.
COVID-19 is mostly spread by respiratory droplets that are airborne when infected individuals cough, talk, or sneeze. The virus may also contaminate hands that touch surfaces with the virus present. It can then be spread to the nose or mouth, resulting in infection. A number of best practices are covered here including handwashing, staying home when sick, and strict environmental cleaning and disinfection that can assist with lowering the risk of infection and viral spread.
Pennsylvania is reopening counties in phases. As of June 20, 2020, all counties are in the green phase except one. Lebanon County remains in the yellow phase. Governor Tom Wolf announced that Lebanon County is slated to move to the green phase of reopening on July 3, putting all 67 counties in green. For up to date information regarding phase status please see the official Pennsylvania government website at https://www.governor.pa.gov/process-to-reopen-pennsylvania/
Phases for Pennsylvania Counties
We also pulled those statements that we thought were most important to the industry. Please refer to the document above for detailed information.
- Red: Businesses are permitted to provide take-out (curbside) and delivery sales only and may not allow the service or consumption of food or beverages on the premises. Also, masks are required.
- Yellow: Businesses are permitted to provide take-out and delivery sales as well as dine-in service in outdoor seating areas as long as they strictly adhere to the state requirements for maximum occupancy limits (see below). Masks are required.
- Green: Businesses are permitted to provide take-out and delivery sales as well as dine-in service in both indoor and outdoor seating areas as long as they strictly adhere to the state requirements including maximum occupancy limits. Masks are required.
- Bar seating may be utilized provided that customers are seated and comply with the physical distancing guideline of at least 6 feet or physical barriers between customers.
- A maximum of four customers that have a common relationship may sit together at the bar, while adhering to the physical distancing guidelines or barriers between other customers.
- Penn State Extension suggestion: Consider providing wine tasting at a table where the patrons are distanced from the pourer/server. That table can be better isolated and an establishment can serve more sets of patrons while avoiding a crowded bar.
State-specific and local guidance from the Pennsylvania Department of Health (updated June 25, 2020)
Please note that the COVID-19 situation is constantly changing and wineries are encouraged to follow updates.
- Follow maximum occupancy limits for indoor/outdoor areas.
- Method 1: Limit to 50% of state fire capacity or 24 people per 1,000 square feet if no fire code is available.
- Method 2: Arrange business so that customers sitting at a table are not within six feet of any customers at another table (this distance would also apply to the tasting bar).
- The Commonwealth will require commonwealth-created “COVID-19 Safety Procedures for Businesses” flyer to be clearly displayed at workplaces, along with publicly posted acknowledgement by the employer that the guidance is being followed. COVID-19-Reopening-Businesses-Flyer-8-5×11-1.pdf
- There is also a requirement to name a “Pandemic Safety Officer” in charge of carrying out COVID-19 safety procedures.
- Masks must be worn by workers and customers while entering, exiting or traveling throughout the business. Patrons may remove masks while seated or eating/drinking.
- Those who cannot wear a mask due to a medical condition are not required to wear one and do not need to provide any documentation of such medical condition.
- Protocols must be established to execute upon discovery that the business has been exposed to a person with probable or confirmed case of COVID-19.
- Employees must be trained on importance and expectation of increased frequency of handwashing, the use of hand sanitizer with at least 60% alcohol, and avoidance of touching the face with hands. Make sure to document all training.
- Provide masks for employees to wear at all times and make it mandatory to wear masks.
- Where possible, stagger work stations to avoid employees standing right next to each other. If not possible, increase frequency of cleaning and sanitizing surfaces.
- Verify that dishwashing machines are operating at the required wash, rinse and sanitize temperatures according to standard protocols.
- Provide physical guides to ensure customers remain at least six feet apart. (ex: tape on floors or sidewalks and signage)
- Assign employees to monitor and clean high-touch areas frequently. (ex: entrance doors, bathroom surfaces)
- Clean and disinfect any shared items that customers come in contact with. (ex: tabletops, digital payment devices)
- Live musicians performing at a restaurant, facility or venue must remain at least six feet from patrons and staff.
The following action items ARE ENCOURAGED according to the order of the governor’s office:
- Establish a written, worksite-specific COVID-19 prevention plan, perform a comprehensive risk assessment of all work areas and designate a person to implement the plan.
- In a risk assessment approach, the facility is divided into various functions and positions. The facility then assesses what could go wrong at each step of the process.
- Controls are then put in place to prevent them from happening.
- For additional information on COVID for Food Establishments and developing a prevention plan form please see the link for an article by Martin Bucknavage and Richard Kralj from the Penn State Extension Food Safety and Quality team entitled COVID Prevention Plan for Food Establishments.
- Links to a COVID risk assessment form developed by the Occupational Safety and Health Administration (OSHA) are provided in the above document. Form examples are included (OSHA is the federal agency that investigates businesses where there is potential for infection).
- Please refer to the webinar “Preparing a COVID-19 Prevention Plan for Retail Food Establishments” for additional important information.
- Prior to each shift, ask that employees self-measure their temperature and assess symptoms. Below are a number of wellness questionnaires that may be utilized for this purpose.
- Use single-use disposable menus (including tasting notes) and discard after each customer. Another option is to list wines available on a chalkboard and ask consumers to select samples from the list. Using reusable menus, other than digital menus sanitized after each use are prohibited in yellow phase.
- Install physical barriers such as sneeze guards and partitions at point-of-sale terminals, cash registers, bars and other areas where maintaining six feet physical distance is difficult.
- Provide hand sanitizer for customers and employees after handling credit cards or cash.
- Schedule closure periods throughout the day to allow for cleaning and sanitizing.
- Use separate doors to enter and exit the business when possible.
For the most up-to-date, reliable information, please continue to refer to the Commonwealth of Pennsylvania’s website for Responding to COVID-19 in Pennsylvania.
Disclaimer: While Penn State Extension makes great efforts to produce the information within these protocols as timely and accurately as possible, we make no claims about the completeness of the contents and disclaim liability for errors or omissions in the contents. Remember that it is important to follow current federal, state and local regulations and guidance.
Note: We will host a panel discussion on the reopening of tasting rooms during COVID-19″ on July 22, 2020 as part of our webinar series. The announcement and registration link will follow soon.
- FDA. Best Practices for Retail Food Stores, Restaurants, and Food Pick-Up/Delivery Services During the COVID-19 Pandemic.
- OSHA. Retail Workers and Employers in Critical and High Customer-Volume Environments.
- CDC. Implementation of Mitigation Strategies for Communities with Local COVID-19 Transmission
- CDC. What to Do if You are Sick
- CDC. June 27, 2020 Considerations for Restaurants and Bars
- AIHA. version 2, June 19,2020 Reopening-Guidance-for-the-Bar-Industry_GuidanceDocument.pdf
- Numerous wellness questionnaire examples are available online (e.g., South Dakota Department of Health’s COVID-19: Employee Screening Questions and Guidelines).BusinessScreening_Q&A.pdf
- PDOH. June 25, 2020 Governor’s Process to Reopen Pennsylvania
- COVID Prevention Plan for Food Establishments. June 2, 2020
- COVID-19 Risk Assessment Form for OSHA Guidelines May, 2020
The Penn State Wine & Grape Team is hosting an online “office hour” session on Tuesday, April 14, from 3 p.m. to 4:30 p.m., to answer any questions you have about your vineyard, winery, and tasting room.
As we explore additional ways to connect with the industry members, the team’s Extension educators and faculty are hosting this Zoom session to answer questions you might have. For example, timely questions related to vineyard management, issues you are experiencing in your winery cellar, marketing strategies for your tasting room, and related.
We look forward to meeting and talking with you.
The Penn State Wine & Grape Team
How can you join the Zoom meeting? Please note that for all of these options you will need to enter this password to proceed: 370146. See the attached PDF, below, for screenshots to lead you through the process when accessing the meeting using a web browser.
To access these Zoom meetings with a PC, Mac, Linux, iOS or Android go to: https://psu.zoom.us/s/229078158
Or to call in dial:
+1 646 876 9923 (US Toll)
Meeting ID: 229 078 158
International numbers available: https://psu.zoom.us/u/aWuWELGMj
Meeting ID: 229 078 158
Please click on the following website to access instructions on how to join a meeting: https://support.zoom.us/hc/en-us/articles/201362193-Joining-a-Meeting
If you are having difficulties accessing these meetings, please contact the Penn State Wine & Grape Team at firstname.lastname@example.org
By Dr. Molly Kelly, Enology Extension Educator, Department of Food Science
Penn State Extension hosted a Fruit Winemaking Workshop on January 29th, 2020 at the Historic Acres of Hershey. The following is a review of the presentation given by Dominic Rivard, internationally-renowned wine professional with over 20 years of experience in wine production. Both a sommelier and winemaker, he specializes in fruit, dessert and ice wines. Dominic is the founder of the Fruit Wines of Canada Association and WinePlanet Consulting and promotes fruit wine sales around the world.
Below is a brief summary of his presentation.
Fruit wine is not a new idea, in fact early American agricultural settlers used fruit wine to preserve seasonal berries. Currently fruit wine consumers are interested in new and unique fruit wines that are local and are looking for a variety of options. Fruit wines are usually refreshing and are relatively easy to drink with many meals and provide an option for those who like sweeter wine.
There are also many documented health benefits with fruit wines such as blueberry wine which is high in Oxygen Radical Capacity (ORC) or antioxidants. The sparkling blueberry wine that was served at the event from Old York Cellars in Ringoes, NJ is advertised as having increased levels of antioxidants.
One advantage of producing fruit wines is that fruit is produced year- round throughout parts of North America. One can also use frozen fruit allowing fruit wine producers to have 4+ production cycles per year.
Fruit wines are becoming accepted as a viable alternative to those made from grapes. They also have export potential. For example, in Asia, a wine is a wine, it does not matter what fruit it is made from. In India fruit wines are sold in supermarkets, five-star hotels and restaurants. Fruit wine is already part of some Asian cultures such as Japan and Korea.
When creating a fruit wine one can begin with a grape base with fruit extract sometimes referred to as “Arbor Mist Style”. One can use a grape base with fruit juice referred to as “Wild Vine Style”. Using fruit juice or concentrate creates a more premium fruit wine or “Serious Style” of fruit wine. There are many different styles of this type of wine including low alcohol, fruit fusion, off-dry, sweet fruit, fortified, sparkling and cryo-extracted style. All of these are unique in their production and create a different type of wine.
Some of the wines tasted at the event were from Pennsylvania including a strawberry wine from Benigna’s Creek Winery in Klingerstown, a peach wine from Shade Mountain Winery in Middleburg and a cranberry wine from Armstrong Winery in Halifax. These wines were well received and many attendees were interested in their production practices.
There are four main steps in producing a fruit wine: pre-fermentation processing, fermentation management, post-fermentation processing and aging. During the pre-fermentation process one must have a plan for harvesting and sourcing the initial fruit product. Then the fruit is crushed, pressed and initial sulfite added. One must also decide if they are keeping the skins on during fermentation or removing them.
Different strains of yeast and bacteria might be added during this time before fermentation begins. During the management process, temperatures must be taken to ensure that it is in the optimal yeast fermenting range. Enzymes should be added to assist in the breakdown of the fruit and complex polysaccharides, allowing the yeast to have substrates to ferment the sugars in the fruit.
Processing ends with the clarification of the wine through filtering, ensuring its enzymatic stability and adjusting the acidity before bottling occurs. After the wine is finished there are many laboratory analyses options for the final product.
The steps listed above are similar to those utilized in grape wine production. There are, however, differences in production depending on the type of fruit used. For additional information you may want to reference Dominic’s book “The Ultimate Fruit Winemaker’s Guide” or other fruit wine production reference. Please contact me with any questions.
By Dr. Molly Kelly, Enology Extension Educator, Department of Food Science
As harvest begins you may want to consider utilizing non-Saccharomyces yeast strains. These strains have been shown to improve aromas, lend complexity and improve mouthfeel. In this post, we will provide an overview of their use and provide information concerning commercial strains available.
The Use of non-Saccharomyces Yeast in Winemaking
The use of S. cerevisiae as a starter culture is the most widespread practice in winemaking. There is, however, an interest in conducting uninoculated fermentations. An uninoculated fermentation is often referred to as a “spontaneous” or “native” fermentation involving the sequential action of various non-Saccharomyces and indigenous Saccharomyces yeasts. The use of “mixed starter” of non-Saccharomyces with strains of Saccharomyces cerevisiae provides an alternative to both “spontaneous” as well as inoculated fermentations. The possible benefits include added complexity, enhanced ability to secrete enzymes important in production of aroma compounds and a fuller palate structure.
The ability of non-Saccharomyces yeasts to produce wines with distinct flavor profiles has increased interest in the use of such yeasts in mixed starters. In addition, research demonstrating the ability of non-Saccharomyces yeasts to lower alcohol content of wines, control wine spoilage and improve additional wine properties have been reported.
Grape musts naturally contain a mixture of yeast species and therefore fermentation is not a “single species” fermentation. During crush, the non-Saccharomyces yeasts on the grapes, cellar equipment and in the environment may come in contact with the must. Cellar surfaces play a smaller role than grapes as a source of non-Saccharomyces yeasts.
It is believed that a selected and inoculated strain of S. cerevisiae will suppress any “indigenous” non- Saccharomyces species and dominate the fermentation process. However, several studies have shown that non-Saccharomyces yeasts can persist during fermentations inoculated with pure cultures of S. cerevisiae.
Non-Saccharomyces yeasts are thought to be sensitive to sulfur dioxide (SO2), poor fermenters of grape must and intolerant to ethanol. It is generally accepted that non- Saccharomyces yeasts, not initially inhibited by SO2, would not survive during fermentation due to combined toxicity of SO2 and alcohol. However, research has shown high numbers (106-108 cells/ml) and persistence of non-Saccharomyces yeasts in some wine fermentations, suggesting their potential role in winemaking.
There are two general practices of inoculation when using non-Saccharomyces yeasts in mixed starters. The first, co-inoculation, involves the inoculation of the selected non-Saccharomyces yeasts at high cell concentration along with S. cerevisiae. The second practice, sequential inoculation, allows initial inoculation of selected non-Saccharomycesyeasts at high levels which are allowed to ferment on their own for a given amount of time before S. cerevisiae is added to complete the fermentation. Although both viable, potential interactions between yeast could determine which strategy is more appropriate. Today, there are available many non-Saccharomyces strains compatible with Saccharomyces strains for the improvement of wine primary aroma. See below.
The most frequently studied species include: Torulaspora delbrueckii, Metschnikowia pulcherrima, Candida zemplinina, Hanseniaspora species and Lachancea thermotolerans).
These yeasts are usually poor fermenters, therefore S. cerevisiae (either indigenous or inoculated) is necessary to take the fermentation to completion. Typically, non-Saccharomyces yeasts have been used in sequential fermentation where they grow or ferment prior to inoculation with S. cerevisiae.
Why use non-Saccharomyces yeast?
What do these “native” yeasts have to offer winemakers and how can they be utilized in a planned and controlled manner to produce desired wine styles? Recently, consumer and market demand for lower ethanol wines has driven some research to develop various approaches to produce these wines. Several studies have reported lower ethanol yields when using non-Saccharomyces yeast. In addition, some non-Saccharomyces yeast can utilize sugars with the production of desirable esters and other flavor/aroma compounds with the added advantage of only minimal production of ethanol.
The variety of flavor/aroma compounds produced by different non-Saccharomyces yeasts is well documented. The compounds produced by different Saccharomyces yeasts include: terpenoids, esters, higher alcohols, glycerol, acetaldehyde, acetic acid and succinic acid. Wine color may also be affected by non-Saccharomyces yeast. Conversely, the improper use of non-Saccharomyces yeasts may result in serious fermentation issues including: stuck/sluggish fermentation, high levels of acetic acid and ethyl acetate, as well as lack of reproducibility etc. The goal of the winemaker is to emphasize the positive impact of non-Saccharomyces wine yeasts while minimizing its negative impact.
There are potential benefits of the use of non-Saccharomyces yeast in wine production; the abundance of grape yeast biodiversity presents many opportunities to explore their use. Strain selection is of key importance, as not all strains within a species will necessarily show the same desirable characteristics. The goals of many researchers have included: efficient sugar utilization, enhanced production of volatile esters, enhanced liberation of grape terpenoids to improve wine flavor and other sensory properties. These goals can be met by selected non-Saccharomyces wine yeast and their proper use in the winery.
Please see links below to information summarized by PSU student Tyler Chandross-Cohen on commercial non-Saccharomyces stains.
Please contact me or your Scott labs representative with any questions.
BIODIVA YEAST: This Yeast was initially sold in a pre-blended kit, partnered with a specific S. cerevisiae strain, but now is isolated for winemakers who can match it with a compatible S. cerevisiae of their choosing for both red and white wines. This isolated yeast makes developing wine more customizable. After creating your own blend, the resulting wines will have more intense aromas, mouthfeel and complexity. The S. cerevisiae strains compatible with Biodiva are 43, BDX, ICV D254, L2056, QA23, and VRB.
FLAVIA YEAST: This yeast is a pure culture of Metschnikowia pulcherrima, which is selected for its ability to produce aroma and flavor revealing enzymes. Flavia is best used with creating aromatic whites and rosés. Flavia will enhance the aroma and flavor profiles of wines optimizing varietal characteristics while bringing freshness and volume in the mouth.
By Dr. Helene Hopfer, Assistant Professor of Food Science, Department of Food Science
In late July of 2019, I was fortunate to be able to participate at the 17th AWITC in Adelaide, Australia. I was invited to speak about our sensory regionality study on commercial Riesling and Vidal blanc wines from Pennsylvania.
Last year, Dr. Kathy Kelley wrote about her sabbatical leave in Australia, and provided an excellent overview into Australia’s wine industry, therefore, this blog post will focus on the presentations and posters at the conference.
TheAustralian Wine Industry Technical Conference & Exhibition (AWITC)is happening every three years, organized by The Australian Wine Research Institute (AWRI)and the Australian Society of Viticulture & Oenology (ASVO). Combining plenary sessions, workshops, poster presentations and a large trade exhibition, the AWITC attracts a large audience (over 1,200 participants this year) primarily from the Australian wine industry. Over 4 days, every aspect of grape growing and wine making, from vineyard to grape vine to enology and wine consumers is covered, providing scientific stimulation and lots of discussion for the industry. Intended to present the latest research findings while at the same time being approachable and transferrable for industry members, the AWITC hosts a wide variety of speakers (academics, industry members, governmental speakers, as well as forward-thinking leaders from other industries). Proceedings and video webcasts of all talks will be made available online on the website, where also all past proceedings are made public. Lots of participants also live-tweeted from the conference, so many impressions can also be found on the official event twitter handle @The_AWITC.
The conference started out with a traditional welcome by a local Aboriginal leader from the Adelaide Plains people. Providing a Welcome to his people’s land and an invitation to learn and work collaboratively, his inspiring speech was a great kick-off to the event, followed by the official opening by the Australian Minister for Primary Industries and Regional Development.
In the first two sessions, the supply and demand for Australian wine and its future were evaluated. Following the official outlook from Wine Australia, Warren Randall provided a thought-provoking talk on China very soon becoming the number 1 wine-consuming nation in the world. Although individual wine consumption for Chinese is estimated to reach 1.6 L per person per year (compare to US consumers averaging to 3.1 L per person per year), the sheer number of Chinese middle-class consumers leads to an estimated additional need of 850 million L within the next 5 years. This additional need equates to 1.2 m tones of grape, about 71% of Australians total annual production! The Chinese will remain to be a net importer, particularly for quality wine – the question is though whether Australia will be able to satisfy this demand, especially with the severe drought many Australian grape-growing regions face.
The subsequent talks reiterated the importance of China as a major Australian wine importer as well as for Australian wine tourism: Brent Hill from the South Australian Tourism Commission presented compelling research showing that wine tourism improves brand recall and sales, independent of winery size. For example, international marketing campaigns in combination with direct flights to Adelaide led to tripling visits from China to wineries in South Australia. Wine tourism also aligns nicely with consumers’ demands for personalized products that align with their values. Health and Well-being are driving consumer preferences and will continue to do so, as presented by Shane Tremble from the Endeavor Drinks Group, a major alcoholic beverage retailer in Australia.
The afternoon session was dedicated to diversity, equity, and inclusivity in the wine industry. Our own unconscious biases create barriers to enter the wine industry, especially for talents from underrepresented groups. Diversity, equity, and inclusivity is not just about social justice, but is a real business loss, especially as the wine consumer base becomes more and more diverse. How can we make sure to meet the needs of our consumers if we don’t really understand them and their needs?
A large portion of the meeting was dedicated to different aspects of climate change and how the wine industry will be able to continue doing business. A representative from a major insurance company presented on her company’s strategy to climate change, and managing risks associated with a changing climate – from special loans for businesses to lower their carbon footprint and greenhouse emissions to ways to manage physical risks such as flooding and bush fires, this presentation was eye-opening. Tools already available for growers, such as high-resolution weather data, provide action-able data for e.g., harvesting or irrigation. Clonal selection, vine training systems and better suited varieties and rootstocks are another tool in the toolbox to adapt to climate change, particularly to higher temperatures and increased incidences of drought, as demonstrated by Dr. Cornelis van Leeuwen from Bordeaux Sciences Agro.
Ending with the conference’s gala dinner, this first day proved to be full of insights and what the future may bring.
The next day started off with the fresh science session, including research on how changing climate will also change insect and disease pressure: Using the example of sooty mold and scale insects, Dr. Paul Cooper presented data and models that show how warmer temperatures will influence occurrence of scale insects and subsequent sooty mold. Similar scenarios could become more prevalent in PA as well, as for example late harvest insect problems could appear at an earlier stage during berry ripening (see also this blog post by Jody Timmer).
On the enology-side, several presentations were given to look at smoke-taint remediation of wines, alternatives to bentonite fining with grape seed powder, and the mechanisms underlying autolytic flavors in sparkling wines. A particular interesting, but also terrifying talk was given by Caroline Bartel from the AWRI on increasing SO2tolerance of Brettanomyces bruxellensis strains: Over the past 3 years, the AWRI has seen an increased number of Brettanomyces strains that show greater tolerance to SO2, some exceeding 1 mg/L molecular SO2!
Biosecurity is a big topic for Australian grape growers, as almost all vineyards are own-rooted, including some of the oldest productive vineyards in the world being over 100 years old! This history is however under threat, as phylloxera has arrived in Victoria and New South Walesa few years ago. Managing the biosecurity threats and best practices to protect vineyards from not just phylloxera but also grapevine viruses was the overarching theme of this session. Showing data from the Napa Valley, Dr. Monica Cooper from UC Extension highlighted the importance of clean plant material when it comes to managing grape vine diseases: in a newly planted vineyard, not enough certified disease-free material was available, and hastily organized vines, infected with red blotch virus, were planted alongside healthy vines. Within a few years, 100% of infected vines had to be removed to avoid spreading of the disease into other parts of the vineyard and adjacent vineyards.
The last talk in the session was given by Dr. Antonio R. Grace from the Portuguese Association for Grapevine Diversity, who argues that clonal selection of grapevines may increase efficiency but decreases resilience, complexity, and diversity.
A particular interesting session was focusing on Agricultural Technology or AgTech – robots, drones, and intelligent robot swarms! A particular impressive and eye-opening talk was given by Andrew Bate from SwarmFarm, a farmer in Queensland who now develops and sells farming robots that oppose the trend for “bigger is better”: using a swarming approach (i.e., many smaller robots that operate autonomously for maximized efficiency and adaptability), he showcased how his approach is forward-thinking and sustainable, and fueled by his own experiences as a farmer and grower. If you can check out the videos on the website!
In a similar inspiring manner, Everard Edwards from the CSIRO presented on low-cost drones and sensors and how to use them in the vineyard to support decision-making: for example, a go-pro camera mounted on a small cart, driving along rows, could be used for yield estimation. The technology is already there, but we are still lacking the data algorithm to make sense out of the data.
The day was finished up with the flash poster research presentations of wine science students. From glycosylated flavor compounds locked up in grape skins, to vintage compression and the effect of very high temperatures (over 50°C/122°F) for a short time on grape berry development and tannin content, these talks showcased the breath of wine research in the various Australian research institutions. Following the evening’s theme, the next day’s fresh science included a talk on how to remediate reductive aromas in wines. Among the tested treatments (DAP addition post-inoculation, donor lees added after malo-lactic fermentation, copper addition, macro-oxygenation, and a combination of copper and macro-oxygenation) macro-oxygenation once a day of 1.5 L/min O2for 2 hours yielded the most promising results while copper addition increased the risk of reductive characters developing post-bottling. Similarly, how to easier measure total and free copper in wines and juice was the topic of Dr. Andrew Clark’s presentation. Working at the National Wine and Grape Industry Centerin Wagga Wagga, Dr. Clark developed an easy spectrophotometric method to accurately and precisely measure free and total copper in wines.
Last, a genetic study on Chardonnay revealed that the same clones (clone 95) shows a different number of mutations depending on where it is from.
Besides the many fascinating talks and the impressive trade show, the meeting also offered lots of opportunities to taste Australian wines. I was lucky enough to participate in a guided tasting of a type of fortified wines unique to Australia: Presented with an impressive number of Rutherglen Muscatwines of all ages and classifications, I was able to experience this special wine style, and must admit that I brought back some bottles of these “stickies”. Made from Muscat a Petit Grains Rouge grapes (literally Muscat with little red berries), very ripe grapes, accumulating very high sugar content, are fermented and fortified with grape spirit, then aged from 3 up to 20+ years in barrels. Wines undergo a solera blending, transferring wines slowly from barrel to barrel until bottling. Flavors range from floral, honey and orange peel all the way to viscous, toasted and caramel flavors. If you ever have the opportunity to taste such wines, I would strongly encourage you to do so – even if this is not your style of liking, it is for sure a worthwhile sensory experience!
Outside of the Conference I also had the chance to visit three remarkable places: The National Wine and Grape Industry Center (NWGIC) in Wagga Wagga, University of Adelaide and the Australian Wine Research Institute (AWRI) in Adelaide, and last, but not least, Penfold’s original winery in the Adelaide Hills for a special tour and tasting of the most expensive wine in Australia, the Grange.
By Dr. Molly Kelly, Enology Extension Educator, Department of Food Science
As we approach harvest, we should be reviewing our sanitation protocols both in the vineyard and winery. In this article we will focus on effective cleaning and sanitizing in the winery, specifically winery equipment to make sure certain objectives are met:
- To continually improve wine quality
- To reduce quality concerns
- To ultimately operate cost-effectively…by annually producing both a quality wine and reaching the targeted financial return
- To reduce food safety concerns
Stainless Steel Winery Equipment
During normal service, all grades and finishes of stainless steel may in fact stain, discolor, or attain an adhering layer of grime. What considerations should one take regarding maintaining stainless steel equipment and the related use of cleaners and sanitizers? The frequency and cost of cleaning stainless steel is lower than for many other materials and often out-weighs the higher acquisition costs. Generally, the frequency of cleaning should be determined by the objective to “clean the metal when it is dirty in order to restore its original appearance.”
So, the degree of cleaning depends on the condition of stainless steel equipment:
- Routine Maintenance – mild cleaning
- Mildly aggressive cleaning to remove minor surface dirt: use sponge or bristle brush with a non-abrasive cleaner and warm water; towel dry. To prevent compromising the integrity of the protective oxide coating on stainless steel, only soft-bristle brushes should be used in the case where scrubbing is required.
- More aggressive, for example, grease: repeat above, then use a hydrocarbon solvent such as acetone or alcohol.
- Aggressive cleaning to remove stains or light rust: use a chrome, brass, silver cleaner and mild non-scratching creams and polishes.
- Most aggressive to remove stubborn mineral deposits: use phosphoric acid (10-15% solution) – apply with a soft cloth and let stand; no rubbing. Follow with ammonia and water rinse; rinse with hot water. Note that nitric acid is effective too but tends to degrade gasket material.
General Cleaning and Sanitizing Sequence:
1. Begin with a cold water, high-pressure rinse. Cleaning with high-pressure is most effective when the spray is directed at an angle to surface being cleaned. One may also use warm water (100-109 F) in high-pressure systems; this tends to reduce time.
2. Use a strong inorganic alkaline solution; such alkaline cleaners effectively dissolve acid soils and food wastes. Examples of alkaline cleaning agents are caustic soda (NaOH), soda ash (Na2CO3), trisodium phosphate (TSP) and sodium metasilicate. Carefully follow instructions because such alkalis are very corrosive to stainless steel if used incorrectly. A mild acid (citric) will neutralize alkaline detergent residues, dissolve the mineral deposits and prevent spotting. As a rule, soda ash rinses better than caustic soda.
3. Continue with a cold water, high-pressure rinse.
4. Sanitizer Options:
a. Water and Steam
- Hot water (180 F) and steam are ideal sterilants: they are noncorrosive, penetrative of surfaces, and effective against juice/wine microorganisms.
- Use hot water for 20 minutes (at 180 F).
- If steam, use until condensate from valves reaches 180 F for 20 minutes.
b. Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.
Note that “acid-anionic” sanitizers such as peroxyacetic acid are effective at lower than ambient temperatures; remove biofilms; and are effective against bacterial spores. The low foam characteristics make them ideal for Clean-in-Place (CIP) applications. Although peroxyacetic acid must be used in well-ventilated area, it is ecologically harmless by decomposing into acetic acid, oxygen, and water.
- Rinse: QAC solutions may leave objectionable films on equipment and should be rinsed off with fresh cold water, high-pressure rinse.
- Final rinse: a hot water, high-pressure rinse. Ideally, heat-sterilized water should be used for this final rinse.
- Ozone treatment (optional)
- NOTE: Remember to remove tank valves, take apart and clean prior to harvest.
There are many different barrel cleaning methods:
- High-pressure water, hot or cold
- Caustic chemicals
- SO2 (in any form: wicks, liquid, gas)
- Dry ice blasting
In selecting which method to use, consider the effects on aroma/flavor extraction, tartrate removal, microbial reductions, water usage, power usage, worker safety, and cost.
The following are recommended cleaning and sanitizing sequences, based on barrel status.
New Barrels/Fault-Free Barrels
- Cold water, high-pressure rinse, 1-3 minutes
- High-pressure steam rinse, 1-3 minutes
- Repeat cold and steam rinses twice more
- Either refill with clean wine or
- Fill with water
- add ozone, if available
- follow with water + 45 ppm SO2/90 ppm citrate
- Fill with water
- After 1-4 days, empty and refill with wine or empty and burn sulfur wick, re-bung, and store; or, if using the gas, inject SO2for three to five seconds.
- If the barrel is to be long-term stored, dissolve and add 45 grams of potassium metabisulfite (KMS) and 180 grams of citric acid; then top the barrel with water. Be sure to top the barrel with plain water every couple of weeks. When you’re ready to use the barrel, empty and rinse twice; then fill with wine.
Likely Fault-Free Barrels, but Unsure
- Sodium percarbonate washes (Proxycarb) are an excellent option for addressing potential off-flavors. Citric acid washes are then used to neutralize residual chemicals. Once the barrel has been cleaned, allow the barrel to dry completely on a rack with the bunghole facing down. Sodium percarbonate is better than hydrogen peroxide: it is more stable at application concentration (100-200 mg/L), has improved compatibility with hard water, and reduced foaming tendencies.
- When the barrel is dry, burn 10-20 grams of sulfur wick per barrel; or, if using the gas, inject SO2 for three to five seconds.
- Place either a paper cup, wooden shipping bung, or other in the bunghole.
- Check sulfur level every 3-4 weeks and re-sulfur as necessary.
Tannin and Tartrate Deposit Removal
- Removal of tannins: Alkaline solutions (soaking with 1% sodium carbonate) are most effective in removing tannins from new barrels. If further treatment is necessary, steam and several rinses should be applied.
- Removal of tartrate deposits: scraping is labor intensive and may injure wood. Instead, use a circular spray head. For stubborn deposits, soaking with 1 kg of soda ash and caustic soda in 100 L of water is effective.
- Option 1: Remove from winery and sell for non-wine uses
- Option 2: Clean, sterilize, and re-use, if worth the cost
- Use same rinse cycles as per barrels without faulty aromas or tastes.
- Fill with water, put steam wand in water and bring water to 160-180°F, steam periodically to maintain temperature for 4-6 hours and
- add ozone, if available
- follow with water + 45 ppm SO2/90 ppm citrate
- After 1-4 days, empty and burn sulfur wick, re-bung, and store.
- After 1-4 weeks, rinse and fill with clean water; after 1 week, take samples and then add 90 ppm SO2/180 ppm citrate while doing microbiological assay of samples.
- If samples are negative for spoilage microorganisms, re-use barrel, but sample periodically.
Bottling Room Equipment
The bottling and packaging function is one of the most critical steps in wine production because there are many opportunities for problems (people with different responsibilities, multiple wines to bottle, and operation and maintenance of multiple equipment stations).
Are sterile bottling rooms necessary? No, but the bottling area should be screened-off from fermentation areas and excessive air movement, and the room itself should have easily sanitized floors, walls, and ceilings.
General Cleaning and Sanitizing Sequence:
- Cold water, high-pressure rinse
- Mild alkaline detergent solution
- Cold water, high-pressure rinse
- Quaternary ammonium compounds (QACs), combined with peroxyacetic acid.
- Cold water, high-pressure rinse
- Sanitization: Hot water and steam used to sanitize bottling line
- 80-90F for 30 minutes
- 180F for 20 minutes; or
- Ozone for 20-30 minutes; or
- Use of iodophors (iodine-based sanitizers): broad-spectrum – active against bacteria, viruses, yeasts, molds, fungi. Follow instructions carefully to avoid potential TCA problems; follow with a hot water, high-pressure rinse.
Prior to bottling, add enough SO2to ensure enough free SO2for 0.8 ppm molecular SO2. Add a little bit extra – to account for free SO2loss during bottling. Generally, target a free SO2that is 10 to 15 ppm higher than the level of free SO2needed for 0.8 ppm molecular SO2. Also, target more or less depending on trauma of bottling method (O2pick up)
Recommendations during operation of the bottling line:
- Wine spills as a source of contamination should be countered by regular and proper cleaning
- Filter-pad trays should be emptied often, and related wine spills quickly rinsed away with a sanitizing agent
- Fill bowls: Mist filler spouts with 70% ethanol to inhibit microbial growth
- Corker: will likely have spilled wine, so use ethanol misting of corker jaws during bottling
- Floor drain gutters should be kept clean by frequent rinsing
- Activity: Limit number of people around the filling/corking area
- Daily sanitation…hot water or steam…20 minutes at 180F
- At least weekly, clean with caustic cleaners followed by hot water sanitation.
- Collect bottles for analysis hourly and immediately after start-up and breaks.
Butzke, C., Barrel Maintenance, Dept. of Food Science, Purdue University, 2007.
Carter, James, There’s a Right Way to Clean and Sanitizing your Facility, Food Quality.com
Donnelly, David M, Airborne Microbial Contamination in a Winery Bottling Room, Am. J. Enol Vitic, Vol 28, #3, 1977
Fugelsang, Kenneth; Edward, Charles G. Wine Microbiology, 2nd Edition, 2010. Springer-Verlag New York Inc. (Chapter 9, Winery Cleaning and Sanitizing)
Marriott, Norman G.; Gravani, Robert B. Principles of Food Sanitation, 5thEdition, 2006. Springer Science + Business Media, Inc. (pp 361-367)
Howe, P., ETS Laboratories, SOWI “Current Issues” Workshops March 2011.
Menke, S., Cleansers and Sanitizers, Penn State Enology Extension, 2007.
Tracy, R. and Skaalen, B. Jan/Feb 2009. Bottling-last line of microbial defense. Practical Winery and Vineyard
Worobo, Randy W., Non-chlorine Sanitizer Options for the Wineries, 33th Annual New York Wine Industry Workshop
Zoecklein, B. et al, Wine Analysis and Production, Aspen Publishers, 1999.
Barrel Care http://www.boswellcompany.com/barrel-care/
Maintaining and Cleaning Stainless Steel http://www.evapco.eu/sites/evapco.eu/files/white_papers/40-Cleaning-Stainless-Steel.pdf
Stainless Steel – Cleaning, Care and Maintenance http://www.azom.com/article.aspx?ArticleID=1182
Taking Care of Your Barrels https://barrelbuilders.com/wp-content/uploads/2016/06/06-16-Barrel-Care.pdf
On March 5, 2019, Penn State researchers and Extension personnel presented research findings and provided five-minute overviews of upcoming studies at the 2019 Wine Marketing & Research Board Symposium, held in conjunction with the Pennsylvania Winery Association Annual Conference.
In this post, we have included short summaries of what each presenter discussed during their session along with a PDF/access to their presentation.
Under-vine cover crops: Can they mitigate vine vigor and control weeds while maintaining vine productivity?
Presented by Michela Centinari, Assistant Professor of Viticulture, Suzanne Fleishman, Ph.D. Candidate, and Kathy Kelley, Professor of Horticultural Marketing and Business Management
Michela, Suzanne, and Kathy discussed research conducted at Penn State related to the use of under-vine cover crops as a management practice alternative to herbicide or soil cultivation. Michela reviewed potential benefits of under-vine cover crops, such as reduction of excessive vegetative growth, weed suppression, and reduced soil erosion. She showed how the selection of cover crop species depends on the production goals of a vineyard, climate, vine age, and rootstock. Suzanne presented results from her research project. She is investigating above- and belowground effects of competition between a red fescue cover crop and Noiret grapevines, comparing responses between vines grafted to 101-14 Mgt vs Riparia rootstocks. Surveys will be administered to Pennsylvania grape growers and wine consumers in the Mid-Atlantic region. Growers will be asked to respond to questions about interest in using cover crops and benefits that could encourage their use. The consumer survey will focus on learning whether cover crops use would impact their purchasing decision and if they would be willing to pay a price premium for a bottle of wine to offset additional production costs.
Impact of two frost avoidance strategies that delay budburst on grape productivity, chemical and sensory wine quality.
Presented by Michela Centinari, Assistant professor of Viticulture
Crop losses and delays in fruit ripening caused by spring freeze damage represent an enormous challenge for wine grape producers around the world. This multi-year study aims to compare the effectiveness of two frost avoidance strategy (application of a food grade vegetable oil-based adjuvant and delayed winter pruning) on delaying the onset of budburst, thus reducing the risk of spring freeze damage. Our objectives are to: i) evaluate if the delay in budburst impacts grape production and fruit maturity at harvest, as well as chemical and sensory wine properties; ii) elucidate the mechanism of action of the vegetable oil-based adjuvant through an examination of bud respiration and potential phytotoxic effects; and iii) assess the impact of the two frost avoidance strategies on carbohydrate reserve storage and bud freeze tolerance during the dormant season.
Toward the development of a varietal plan for Pennsylvania wine grape growers.
Presented by Claudia Schmidt, Assistant Professor of Agricultural Economics, and Michela Centinari, Assistant Professor of Viticulture
Claudia Schmidt is a new Assistant Professor of Agricultural Economics with an extension appointment at Penn State. Claudia used the opportunity of the symposium to introduce herself to the industry. In her presentation, she first gave an overview on what and where Pennsylvanians buy their wines and spirits. She then talked about the research needed to develop a varietal plan for the Pennsylvania grape and wine industry to match existing and future grape production and variety suitability with anticipated consumer demand. The immediate next steps on her research agenda are to develop a baseline survey of grape production in Pennsylvania and, in collaboration with Michela Centinari, region specific cost of production of grapes.
Survey for grapevine leafroll viruses in Pennsylvania: How common is it, and how is it effecting production and quality?
Presented by Bryan Hed, Research Technologist
This is a continuing project funded by the PA Wine Marketing and Research Board, that has focused on the determination of the incidence of grapevine leafroll associated virus 1 and 3 (the two most economically important and widely distributed of the leafroll viruses) in commercial vineyard blocks of Cabernet franc, Pinot noir, Chardonnay, Riesling, and Chambourcin, across the Commonwealth. Over two years, the survey has shown that grapevine leafroll associated viruses 1 and/or 3, were present in about a third of the vineyard blocks examined. Infection of grapevines by grapevine leafroll-associated viruses can have serious consequences on yield, vigor, cold hardiness, and most notably fruit/wine quality. Bryan also discussed a second phase of the project, anticipated to continue for at least another two years within 6 vineyard blocks of Cabernet franc, identified in the survey. In these vineyards, we plan to plot the spread of these viruses, examine and report their effects on grapevine vegetative growth, yield, and fruit chemistry, and characterize the influence of inter- and intra-seasonal weather conditions on virus-infected grapevine performance.
Integrating the new pest, spotted lanternfly, to your grape pest management program.
Presented by Heather Leach, Extension Associate
Spotted lanternfly (SLF) is a new invasive planthopper in the Northeast U.S. that threatens grape production. Heather covered the basic biology, identification, and current distribution of SLF. She also presented on the economic impact of SLF in the grape industry and ways to manage SLF in your vineyard. SLF can feed heavily on vines causing sap depletion in the fall which has resulted in death of vines, or failure of vines to set fruit in the following year. While biological controls such as pathogens and natural enemies along with trapping and behaviorally based methods are being researched, our current management strategy relies on using insecticides sprayed in the vineyard. Heather showed results from the 2018 insecticide trials conducted against SLF, with efficacy from several products including bifenthrin, dinotefuran, thiamethoxam, carbaryl, and zeta-cypermethrin. You can read more about the results from this trial here: https://extension.psu.edu/updated-insecticide-recommendations-for-spotted-lanternfly-on-grape
Five-minute research project overviews
Impact of spotted lanternfly on Pennsylvania wine quality.
Presented by Molly Kelly, Extension Enologist
The Spotted Lanternfly (SLF) presents a severe problem both due to direct damage to grapevines as well as their potential to impact wine quality. Insects are known to produce or sequester toxic alkaloid compounds. The objectives of this study include characterizing the chemical compounds in SLF and production of wines with varying degrees of SLF infestation. We can then provide winegrowers with recommendations for production of wine from infested fruit. Toxicity studies will be conducted to determine the levels of toxic compounds in finished wine, if any, using a mouse bioassay.
Exploring the microbial populations and wild yeast diversity in a Chambourcin wine model system.
Presented by Chun Tang Feng, M.S. Candidate, and Josephine Wee, Assistant Professor of Food Science
In Dr. Josephine Wee’s lab, we are interested in the microbial population and diversity associated with winemaking. When it comes to wine fermentation, not only are commercial yeasts involved in this process, but also many indigenous yeasts. Our research goal is to isolate the wild yeasts and assess their feasibility of wine fermentation. We are expecting to explore the unique yeast strains from local PA which are able to make a positive impact on wine flavor.
Rotundone as a potential impact compound for Pennsylvania wines
Presented by Jessica Gaby, Post-Doctoral Scholar and John Hayes, Associate Professor of Food Science
This study will examine Pennsylvania consumers’ perceptions of rotundone with the goal of determining whether a rotundone-heavy wine would do well on the local market. This will be examined from several different perspectives, including sensory testing of rotundone olfactory thresholds, liking and rejection thresholds for rotundone in red wine, and PA consumer focus groups. The ultimate aim of the study is to determine the ideal concentration of rotundone in a locally-produced wine that would appeal to PA consumers.
Defining regional typicity of Grüner Veltliner wines
Presented by Stephanie Keller, M.S. Candidate, Michela Centinari, Assistant Professor of Viticulture, and Kathy Kelley,
Grüner Veltliner(GV) is a relatively new grape variety to Pennsylvania, and while climatic conditions are favorable to its growth, the Pennsylvania wine industry is still becoming familiar with the varietal characteristics of GV grown and produced throughout the state. This study focuses on defining typicity of Pennsylvania-grown GV wines. Typicity is described as the perceived representativeness of a wine produced from a designated area, and defining typicity can improve wine marketing strategies. This study uses multiple experimental sites across the state to create wines from a standardized vinification method. The wines will be analyzed using both instrumental and human sensory methods.Surveys will be administered to Pennsylvania grape growers and white wine consumers in the Mid-Atlantic region. Growers will be asked their interest in growing GV and what perceived and real barriers may impact their decision to grow the variety. The consumer survey will focus on understating how to introduce them to a wine varietal they may be less aware of and what promotional methods may encourage them to purchase the wine.
Boosting polyfunctional thiols and other aroma compounds in white hybrid wines through foliar nitrogen and sulfur application?
Presented by Ryan Elias, Associate Professor of Food Science, Helene Hopfer, Assistant Professor of Food Science, Molly Kelly, Extension Enologist, and Michela Centinari, Assistant Professor of Viticulture
The quality of aromatic white wines is heavily influenced by the presence of low molecular weight, volatile compounds that often have exceedingly low aroma threshold values. Polyfunctional varietal thiols are an important category of these compounds. This project aims to provide research-based viticultural practices that could lead to increases in beneficial varietal thiols in white hybrid grapes. The expected increase in overall wine quality will be validated both by measuring the concentrations of these desirable compounds (i.e., thiols) in finished wines using instrumental analysis and by human sensory evaluation, thus providing a link between the viticultural practice of foliar spraying and the improvement of overall wine quality.
By: Conor McCaney, Graduate Assistant, Department of Food Science & Technology
The winemaking process is a dynamic one: from crush, to fermentation, on to post fermentation cellar procedures, aging, and bottling. Each step along the way allows for the potential ingress of oxygen, whether wanted or not. While oxygen is considered by many to be the enemy of wine, this is not always the case. In fact proper use of enological oxygen at crucial steps in the winemaking process is paramount to wine development. That said, many winemakers dutifully aim to eliminate it from the process altogether particularly in partial tank headspace. Proper gassing regimens and selection of the correct gas for a particular application is something that many do not do well and fail to fully understand the principals at play. Managing proper inert gas procedures is tricky. Most protocols are generally arbitrary ones copied from bad information and the proliferation of poor techniques passed on anecdotally from winemaker to winemaker. In general it is a procedure that is often over looked and never given much thought. This usually means the use of a high pressure cylinder (most often nitrogen), and a ¼” or ½” hose that is allowed to run for an arbitrary amount of time, generally 15 to 20 minutes. The results are the improper use of inert gases from the failure to measure gas volumes delivered (using a flowmeter), monitoring results with the use of a dissolved oxygen meter, using an under or oversized delivery system and unsubstantiated cost analysis pertaining to gas type and volume needed.
Typical gas choices are: carbon dioxide, nitrogen, and argon. Most wineries choose to use carbon dioxide and nitrogen because they believe it provides the best cost-benefit in terms of oxygen displacement per unit cost. This is not the case. To understand this, we must first delve into some fundamental principles of gases. In the wine industry, we typically use gas by volume, either in standard cubic feet or molar volume delivered from a standard steel pressurized cylinder in which the gas is compressed. These gas volumes are usually measured at 25°C and 1 atm. If you happen to purchase gas by the pound it is necessary to divide the gas by its molecular weight before you can compare gases to one another. The approximate molecular weights are: 40 g/mole for argon (Ar), 44 g/mole for carbon dioxide (CO2), 28 g/mole for nitrogen (N2), and 29 g/mole for air. One mole of any of these gases measured at standard pressure (1atm) and temperature (25°C) occupies one molar volume, roughly equivalent to 22.4 liters, 5.92 gallons, or 0.8 standard cubic feet. Using the ideal gas law PV = nRT the behavior of gases can be described in which pressure and volume is a fixed proportion in relation to the number of moles of gas at absolute temperature. This indicates that gas molecules take up the same amount of space regardless of their mass when they are at the same temperature and pressure (Avogadro’s Law). Thus one mole of any gas contains the same number of molecules (i.e., 6.02 x 1023). This also indicates that the head space in a tank, barrel, or other container will fluctuate regularly throughout the day in response to temperature and pressure changes. Tanks that are kept outside experience greater temperature changes throughout the day compared to a tank kept inside at a constant temperature. Changes in barometric pressure and temperature can cause the headspace in a tank to pump 3% to 7% of its volume in and out daily. This ultimately means that the headspace in a tank is not a static system and could be constantly changing.
Air is roughly composed of 78% nitrogen, 21% oxygen, and 1% argon, so in essence nitrogen is air without the oxygen. In any gassing procedure it is ideal to reduce the percentage of oxygen in the headspace to below 1% or even below 0.5% to inhibit the growth of aerobic microbes and prevent wine oxidation. The most commonly used gas in winemaking is nitrogen (N2) with a molecular weight (MW) of 28 g/mole making it moderately lighter (less dense) than air at 29 g/mole MW. Graham’s law of diffusion (also known as Graham’s law of effusion) states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass at constant temperature and pressure. This principle is often used to compare the diffusion rates of two gasses such as nitrogen and air. The diffusion rates of nitrogen and air are almost identical meaning that nitrogen does not provide adequate layering, but rather readily mixes with air and does not remain in contact with the wine surface for an extended period of time. This also means that in order to reduce the O2level from 21% to less than 1%, the headspace needs to be flushed with a volume of nitrogen that is five times the volume of the headspace. So if the tank has a 100 gallons of head space it would take 500 gallons of nitrogen to reduce the O2level from 21% to below 1%. The cost of nitrogen is approximately $0.05 per cubic foot (Praxair, Inc). However, because nitrogen requires five times the volume equivalents to reduce the O2percentage from 21% to less than 1%, the cost to gas a barrel (60 gallons) is $2.00, 100 gallons of headspace is $3.34 and 1,000 gallons of headspace is $33.42. This is significantly higher than the cost of using argon for the same O2reduction in the equivalent headspace volumes. This is why headspace gassing with nitrogen requires a substantial effort and time commitment on the part of the winemaking team to be effective. It takes substantially more nitrogen and a greater application time compared to argon to achieve the same reduction in oxygen percentage with a shorter effective shelf life.
In contrast to nitrogen is carbon dioxide (CO2), which is significantly heavier than air at 44 g/mole compared to 29 g/mole and by Graham’s law has a much slower rate of diffusion compared to air. This allows for a more significant displacement of air compared to nitrogen. However, when CO2is delivered from a compressed tank, it is difficult to achieve the desired laminar flow necessary for successful layering. This results in substantial mixing of CO2and air. A more effective alternative for CO2delivery is dry ice (solid CO2) which leads to more efficient layering of CO2and subsequent displacement of air but does not form a permanent layer. However, it should be noted that CO2cannot be considered inert in the same way as nitrogen and argon. Because of Henry’s Law, which states that the solubility of a gas is directly proportional to the partial pressure of the gas above the solution, CO2readily dissolves into wine under standard conditions and its solubility can be increased or decreased with changes in pressure. This dissolution of CO2into the wine causes the pressure in the tank to fluctuate and results in the intake of air from the outside environment through an airlock to replace the lost volume of gaseous CO2. If there is no vacuum release valve on the tank, this could cause the tank to implode. Carbon dioxide dissolved in the wine will also alter the acid, flavor, and textural profile of the final wine. Carbon dioxide is much more effective when deployed early in the winemaking process at juice stage or when the wine is young as there will be substantial time to allow excess dissolved CO2to come out of solution. The use of dry ice to protect grape must is an effective way to protect wine must from excess oxygen exposure, deter fruit flies, and subsequently cool the must.
This leaves argon with a molecular weight of 40 g/mole, making it substantially heavier than air (29 g/mole) and similar in weight to CO2but more inert. A major opposition to the use of argon regularly in wine production is because it is significantly more expensive compared to the other two gases. It is true that when purchasing gas by volume argon is roughly three times as expensive as nitrogen or carbon dioxide. However it is much more effective at displacing air and creating a more permanent blanket that remains in contact with the wine surface longer while also remaining inert compared to CO2. Less volume is also needed to achieve the same desired results. At approximately $0.11 per cubic foot (Praxair, Inc) not including daily tank rental fee, a barrel (60 gallons) can be completely gassed with argon for $0.88, 100 gallons of head space for $1.47, and 1,000 gallons of headspace for $14.71. This cost is relatively insignificant to a winery’s bottom line in terms of the degree of quality preservation that argon can provide.
When using any of the gases discussed previously, it is important to select the proper pressure gauge, hose diameter, hose length, flowrate, and the use of a t-valve in order to deliver the gas under laminar conditions. The use of a lower velocity, will encourage laminar flow delivery and reduce any chance of turbulence and subsequent mixing with air, thus creating a more layered effect.
It is ideal to keep the flow velocity to 1 meter per sec or less. To determine the velocity divide the volumetric flow rate in cubic meters per second by the cross sectional area in meters of the hose being used. If using cubic feet instead of cubic meters, perform the same calculation but convert the units from cubic meters to cubic feet and meters to feet. Table 1 shows that it is best to use a 1.5” or 2” diameter line with a t-valve to deliver an adequate amount of gas in a reasonable amount of time. This will require the use of an oversized regulator compared to the typical 0.25” regulator used on most compressed gas cylinders.
In essence it is best practice to recommend the use of argon as the headspace gas for the majority of wine production processes. Carbon dioxide and nitrogen have their respective roles but when it comes to headspace gassing argon it the number one choice. In the production of high quality wine, it is imperative to establish proper gassing procedures. This includes the successful training of staff in all aspects of gassing procedures and the selection of the correct gas for the appropriate task. This also requires selecting the correct regulator size, hose diameter and length, the use of T-valves, measuring gas flow using a flowmeter, and finally verifying results with the use of a dissolved oxygen meter to monitor oxygen levels in the tank headspace pre and post gassing. The proper investment of time and resources in this often overlooked area of winemaking can have a profound effect on wine quality and preservation in the long run. It can also reduce long term costs by reducing the amount of gas and time required to achieve the desired reduction in the amount of oxygen present in a tank headspace.