2017 PA Research Symposium Provides Research-Based Practicality for PA Grape Growers and Winemakers

By: Denise M. Gardner

The Pennsylvania Wine Marketing and Research Board (PA WMRB) annually awards researchers and graduate students grants to explore pertinent topics to the Pennsylvania wine industry.  For the 2016 – 2017 fiscal year, four projects were awarded industry-funded grants.  Results from these four projects will be presented at the 2017 Symposium, co-hosted by the PA WMRB, Penn State Extension, and the Pennsylvania Winery Association (PWA).

Registration is being organized through the PWA, and can be found here:


This year’s Symposium, held on Wednesday, March 29th at the Nittany Lion Inn (University Park, PA) will only run in the morning and is packed with 5 sessions of information pertinent to both the enology and viticulture fields in Pennsylvania.  At the close of the Symposium a lunch will be provided for all attendees.

Guest Speaker has Enology and Tannin Focus

The WMRB Symposium key guest speaker is Dr. Catherine Peyrot des Gachons, Winemaker Consultant at Chouette Collective.  Dr. Peyrot des Gachons has assisted Pennsylvania wineries with enhancing their quality production for several years.  She will be speaking towards her tannin and wine aroma matrix research that she has been working on at the Viticulture and Enology Department through the University of Montpellier (France).

Dr. Catherine des Gachons, winemaker consultant, will be the key guest speaker at the 2017 PA Wine Marketing & Research Board Symposium.

Dr. Catherine des Gachons, winemaker consultant, will be the key guest speaker at the 2017 PA Wine Marketing & Research Board Symposium.

Tannins: Modulation of wine structure and aroma

From environmental factors on tannin biosynthesis to human interventions to modulate tannin content in wine what do we know and what can we do to modulate wine structure. Can this tannin content impact wine aroma?  The presentation will focus on few main points of interest with practical applications.


Enology-Focused Presentations

An additional enology-based presentation will feature Laurel Vernarelli, a graduate student in Dr. Ryan Elias’s lab within the Penn State Department of Food Science.  Laurel’s presentation will be an extension from Dr. Gal Kreitman’s work that was presented last year on predicting reductive off-odors in wines.  Laurel will explore the use of copper fining in wine production and the potential impact it may have on wine quality.  Given the prevalence of reductive off-odors, including hydrogen sulfide, and heavy reliance on copper fining, this topic should be of considerable interest to most wineries.

Laurel Vernarelli will give an update on treating reductive and hydrogen sulfide aromas/flavors with copper sulfate at the 2017 PA Wine Marketing & Research Board Symposium.

Laurel Vernarelli will give an update on treating reductive and hydrogen sulfide aromas/flavors with copper sulfate at the 2017 PA Wine Marketing & Research Board Symposium.

Reconsidering copper fining in wine

This presentation will include a brief overview of copper fining, along with the impact of reductive thiols and recent findings describing the effect that copper has in wine. A method for using immobilized copper materials in place of copper fining is described. Depending on the result obtained, winemakers can make informed decisions for use of alternative fining techniques when dealing with reductive issues.


Viticulture-Focused Presentations

For those with an interest in viticulture, this year’s program promises to deliver some key updates.  Bryan Hed, Research Technologist for the Department of Plant Pathology, will present his annual updates regarding disease management for Pennsylvania vineyards.  For those that are frequent blog followers, Bryan is a lead contributor to the important seasonal reviews.  These tend to be very popular posts for growers and his presentations are always informative and practical.  If you missed the 2016 seasonal reviews, you can find them here:

Bryan’s talk at this year’s Symposium is a continued study with results collected over 2 years, which helps initiate trends and suggestions useful towards growers.

Bryan Hed from Penn State University will review current disease management techniques for the vineyard at the 2017 PA Wine Marketing & Research Board Symposium.

Bryan Hed from Penn State University will review current disease management techniques for the vineyard at the 2017 PA Wine Marketing & Research Board Symposium.

Updates on Grape Disease Management Research

Fruit zone leaf removal can be a very beneficial practice in the management of harvest season bunch rot. Bryan will start his presentation by briefly reviewing the pros and cons of different timings of this practice. In addition, leaf removal by hand is very expensive and labor intensive, and with the increasing scarcity and rising cost of hand labor, mechanization is crucial to increasing cost effectiveness and adoption of this practice, no matter what the timing. Bryan will follow up with an in depth discussion of the progress made toward mechanizing an early, pre-bloom leaf removal and comparing its effectiveness over a variety of wine grape cultivars and training systems during the past two seasons.


Maria Smith, Ph.D. candidate in Dr. Michela Centinari’s lab, will discuss her research regarding early leaf removal in Gruner Veltliner vines.  Maria and Dr. Centinari have previously written a blog post pertaining to leaf removal strategies for Mid-Atlantic vineyards, which could act as an excellent primer to Maria’s presentation in March.  Her presentation will deliver two-years (2015, 2016) of data regarding the effects of early leaf removal and cluster thinning techniques on Gruner Veltliner vines.

Penn State Plant Science Ph.D. Candidate, Maria Smith, will discuss her research on early leaf removal and cluster thinning techniques for Gruner Veltliner at the 2017 PA Wine Marketing and Research Board Symposium.

Penn State Plant Science Ph.D. Candidate, Maria Smith, will discuss her research on early leaf removal and cluster thinning techniques for Gruner Veltliner at the 2017 PA Wine Marketing and Research Board Symposium.

Vine response and management costs of early leaf removal for yield regulation in V. vinifera L. Gruner Veltliner

Early leaf removal (ELR) and cluster thinning (CT) were applied and compared for yield regulation in Grüner Veltliner over the 2015 and 2016 growing seasons.  Early leaf removal was performed at two different times, trace-bloom and fruit-set. We compared the effects of ELR and CT on grape quality, vine health, and economic costs to un-thinned vines.


Finally, Dr. Michela Centinari will follow up with further results regarding sprayable products to reduce frost damage in wine grape vineyards.  Michela’s frost research has been a prominent topic at previous Symposiums, and is often featured here on the blog site.  While the updated results that will be presented at the 2017 Symposium have not yet been reported through Penn State Extension, please see some of her past blog posts pertaining to frost control and freeze damage in the vineyard:

Dr. Michela Centinari will discuss her current research findings pertaining to frost protection in the vineyard at the 2017 PA Wine Marketing & Research Board Symposium.

Dr. Michela Centinari will discuss her current research findings pertaining to frost protection in the vineyard at the 2017 PA Wine Marketing & Research Board Symposium.

Spray-on materials: can they reduce frost damage to grapevines?

Dr. Centinari will present results of studies conducted to test the efficacy of sprayable products as a low-cost frost protection strategy. Two materials Potassium-Dextrose-Lac (KDL) and a seaweed extract of Ascophyllum nodosum, were tested for their cryo-protective activity using a controlled-freezing technique on several grapevine cultivars.


We hope to see you there!

A Pruning Primer

By: Andrew Harner and Michela Centinari

As we move forward through the winter season, many growers have begun or are planning on beginning their annual dormant pruning within the coming weeks. Though a routine task within the vineyard, dormant pruning is essential to maintaining a balanced vineyard that produces quality fruit. With that in mind, this post will both review the basics of dormant pruning and present a series of important considerations to keep in mind when pruning and planning to prune.

With that being said, we will begin with the basics: What is dormant pruning?

In short, dormant pruning is the intentional removal of grapevine tissue, in the form of canes, cordons, trunks, etc., during the annual period of plant dormancy.

What are we trying to gain or change through dormant pruning?

In order to understand the rationale and goals behind dormant pruning, it is first important to understand the biology of grapevines and their physical characteristics that have evolved over thousands of years. Grapevines behave as lianas, or woody, lignified vines that lack a specific growth form on their own; instead, they use other means of support for their growth (i.e., trees or trellis wires). Moreover, grapevine shoots exhibit an indeterminate growth pattern and will continue to grow as long as growing conditions allow and are hospitable. This helps explain why the wild grapevine species endemic to North America tend to be sprawling masses of extensive shoots, and overall have a vigor that differentiates grapevines from many other fruit crops. As a whole, they will remain in this vegetative state until there is access to sufficient sunlight to induce floral development.

Both trellising and pruning are means of harnessing this inherent productivity, with the goal of transitioning it into reproductive growth and consistent, quality fruit yields. Dormant pruning is the primary tool used by grape growers to maintain vine shape, as defined by the training system, and to effectively regulate crop load (fruit mass/vine size) so that a vine’s bearing capacity matches its vegetative vigor capacity. This balance is especially important, as over- or underestimating a vine’s capacity to ripen a fruit crop may result in overly vigorous or overly cropped vines, both of which can have long- and short-term negative consequences. Additional crop load adjustments through shoot thinning and cluster thinning may also be necessary during the growing season to fine-tune grapevine crop load.

Principles of vine balance and essential considerations  

Various efforts by researchers to quantify the effects of pruning on vine performance have resulted in the establishment of a few metrics that can be used to guide dormant pruning. Perhaps one of the most basic but important ways to measure vine size is through the collection and weighing of the canes removed by pruning (Figure 1). These numbers could be used to compare final vegetative biomass between vines of any given season, and when combined with the crop yield measurement—taken on the same vines at the previous harvest—can be used to calculate the ratio of fruit yield to vegetative mass. This ratio is the basis for the Ravaz index (yield/pruning weight), an early metric of vine balance first pioneered by the French viticulturist Louis Ravaz during the early 20th century.

Figure 1. A local grower collecting pruning weights. Photo credit: Mark Chien.

Figure 1. A local grower collecting pruning weights. Photo credit: Mark Chien.

Otherwise called crop load, optimal Ravaz index values vary by grapevine species and variety: research on Vitis vinifera has suggested that optimal crop load values fall between 5 and 10; a Ravaz index below 5 indicates that vines were potentially under-cropped (a small vine with a large crop), while a Ravaz index close or above 10 indicates that vines may have been over-cropped (a small vine with a large crop). American and Canadian studies have suggested that interspecific hybrid varieties, more of which are grown in Pennsylvania and other regions of the northeast and Midwest US, are capable of achieving higher crop load values without compromising fruit quality.

Caution is still necessary when thinking about crop load, however, as these general ranges fail to detail variations in a vine’s capacity to ripen its crop due to genotype, weather, soil, and management strategies. Exceptions can occur, and often do occur. While any variety may produce high yields with good fruit quality at one site – and subsequently attain high Ravaz index values – the same variety may not be able to ripen the same amount of fruit at less vigorous sites and under different weather conditions (i.e., locations with shorter growing seasons and/or with lower heat accumulation).

The concept of balanced pruning focuses on cropping vines at yields that are tailored to the vine’s vigor potential and size. The goal is to prevent under- or overcropping and ensure proper shoot maturity and winter-hardiness through a conscious approach to pruning: for example, more vigorous vines are allocated a greater number of buds so the vegetative growth potential is spread across a greater number of nodes, resulting in lower individual shoot vigor. In terms of managing weaker vines, fewer buds are to be retained so the remaining buds will produce more vigorous shoots.

Figure 2A & B. A before-and-after photographical comparison, showing a vigorous vine before pruning (A) and the same vine following pruning (B), in which 4 canes are left instead of 2 in order to better regulate and take advantage of the vine’s vigor.

Figure 2A & B. A before-and-after photographical comparison, showing a vigorous vine before pruning (A) and the same vine following pruning (B), in which 4 canes are left instead of 2 in order to better regulate and take advantage of the vine’s vigor.

Simple model equations have also been developed for balanced pruning that allocate specific numbers of nodes based on total pruning weights. A classic example is the equation for Concord vines: 30+10, where 30 nodes are retained for the initial pound of pruning weight, and 10 nodes retained for every additional pound of pruning weight thereafter. This specific formula is unsuitable for hybrid and V. vinifera vines, however, as Concord vines are typically cropped at higher levels. Other suggested formulas are based on cluster size, with large clustered varieties (e.g., Chancellor) at 20+10, small clustered varieties (e.g., Marechal Foch) at 20+10, and medium clustered varieties at 10+10. Varieties with large clusters and highly fruitful shoots tend to overcrop, so additional cluster and shoot thinning may be necessary for optimal balance; this counteracts any overcropping that could potentially occur if the formula is followed strictly. Again, these formulas are not the rule, and exceptions to them ­can and will occur. Instead, it is immensely important to use them as a guideline and tailor final node counts to the individual vine or variety, while keeping in mind site and variety vigor, climate, soil type, and training system.

What differences exist between cane and spur pruning?

Depending on the type of training system implemented and the variety being pruned, dormant pruning methodology consists of either cane pruning or spur pruning. The difference lies in the length of bearing unit, or the one-year old wood, retained: spurs are typically 2-3 nodes long, whereas canes are longer – usually between 8 to 15 buds.

With spur pruning, the one-year old fruiting canes are pruned back to spurs of 2-3 nodes, being the fruiting wood that will yield new shoots in the subsequent growing season. This allows for the retention of cordons and mature, wooden arms (Figure 3).

Figure 3. Spur-pruned vines. A) Cabernet Sauvignon vines with equally spaced, fruitful 2-bud spurs at the Alson H. Smith AREC, Virginia Tech. University. B) A two-bud spur. Photo credit: C. Intrieri.

Figure 3. Spur-pruned vines. A) Cabernet Sauvignon vines with equally spaced, fruitful 2-bud spurs at the Alson H. Smith AREC, Virginia Tech. University. B) A two-bud spur. Photo credit: C. Intrieri.

Conversely, cane pruning entails the removal of one-year old growth back to the head or crown of the vine, with the retention of two canes – one for each side of the trunk – for the bilateral training systems that are used in many vineyards in the eastern US (Figure 4). In sites with high vigor potential, growers may choose to leave four canes instead of two (Figure 2A & B, and Figure 5), which will help to accommodate more vigor and leave the vine more balanced. Furthermore, choosing canes of the right size is especially important—the preferred cane diameter is within a range of 3/8 to 1/2 inch, easily represented by the diameter of a pencil—as thick, excessively vigorous bull canes are as unsuitable as thin, spindly canes. Canes that are too thin or too thick will only yield shoots and fruit of inconsistent quality, whereas well-matured canes with diameters within the mentioned range will only help with maintaining full canopies and fruit-bearing capacity.

Figure 4. Bilateral, cane-pruned vines that each have two canes tied down to the trellis wire. Photo taken at a commercial vineyard in Pennsylvania.

Figure 4. Bilateral, cane-pruned vines that each have two canes tied down to the trellis wire. Photo taken at a commercial vineyard in Pennsylvania.

Figure 5. Another example of cane pruning to 4 canes to accommodate vigorous vegetative growth. Photo taken at a commercial vineyard in Pennsylvania.

Figure 5. Another example of cane pruning to 4 canes to accommodate vigorous vegetative growth. Photo taken at a commercial vineyard in Pennsylvania.

Choosing the right pruning system is dependent upon many factors: the variety being grown is especially important, as basal buds of some varieties (e.g., Sauvignon blanc, Nebbiolo) have low fruitfulness and are therefore unsuitable for spur pruning. Vine spacing, mechanization, available labor, and time availability may also affect the choice of a pruning technique. Cane pruning requires more labor in the form of tying down canes, but cane-pruned vines generally require less shoot thinning during the growing season. It is therefore important to select canes with equally spaced internodes, as this allows for equally spaced shoots and reduced shoot crowding.

If the vines are spur-pruned, retaining equally spaced spurs is crucial in order to obtain uniform canopy density and improved sunlight penetration, though shoot thinning during the growing season will likely be necessary as well. Regardless of the pruning method chosen, maintaining sunlight into the renewal zone is essential, as poor light penetration will inhibit bud fruitfulness with negative consequences for future yield and fruit quality.

How do I know when to prune? Pruning strategies for cold climate viticulture

Regardless of the seemingly obvious answer that dormant pruning should be implemented during the dormant, winter season, the timing of pruning could have major implications for the following season’s growth.

In grape-growing regions where there is risk of exposure to damaging cold events, such as Pennsylvania, pruning during the late winter is preferred. Low winter temperature events can damage buds and vascular tissues of mainly cold-tender vine varieties – all vines have limits to their cold-hardiness, however, and even very cold-hardy hybrids can sustain injury to buds and other tissues under exceptionally cold events.

Pruning in the late winter would allow growers a chance to assess vine injury and accordingly adjust the number of buds/nodes to retain. Yet due to labor and time constraints, it is often not possible to do all pruning in the late winter; instead, it is best to begin with the most cold-hardy varieties and leave more cold-susceptible varieties until later in the season. Moreover, in an instance where a damaging cold event does occur, various levels of additional buds are recommended for retention during pruning, depending on the percentage of bud necrosis (Table 1). A high level of bud injury might require differing pruning strategies, such as retraining new trunks and renewing larger parts of the vine, but these topics will not addressed within this post.

Table 1. Bud mortality thresholds and recommended adjustments to pruning strategy. Adapted from Willwerth et al., 2014.

Table 1. Bud mortality thresholds and recommended adjustments to pruning strategy. Adapted from Willwerth et al., 2014.

When forming a plan for pruning, it is equally important to consider the topographic and microclimatic variability of a vineyard site, as this has implications for air drainage. Vines, rows, or blocks that are at lower elevations than the rest of the vineyard may be more susceptible to cold temperature injury if dense, cold air drains to these low points and pools there. This creates pockets of air that will have lower temperatures than the ambient temperatures of any surrounding blocks, rows, etc. that are at higher elevations.

This is also a consideration worth keeping in mind as the season progresses to bud-break, as these same microsites are also more susceptible to damaging spring frosts and could have any early season growth quickly curtailed. In these cases, double-pruning can be a potential strategy when spur-pruning: canes are first pruned back to long spurs/canes of 5-8 buds, which will allow for terminal bud growth first and will suppress basal bud growth due to apical dominance. Once the risk of frost has passed, a final pruning cut should be made to cut the spurs back to 2-bud spurs. An alternative for cane-pruned vines would entail leaving long canes and extra canes until the threat of frost has passed, and then subsequently making a final pruning cut that leaves the canes at the desired bud number.

Through this post we have hoped to provide an overview of balanced pruning methodology, as well as emphasize considerations that are essential to successful pruning and maintaining balanced, fruitful vines. We realize that many growers tend to have their own styles and methods of pruning, however, and their own rationale for using specific strategies that may differ from the ones listed here. We would be happy to hear about their systems, and any strategies that have proven successful for their vineyards and vines, or adaptations they have implemented to handle specific circumstances or issues within the vineyard. Please feel free to contact us with your ideas and experiences regarding dormant pruning.

Additional Resources

In addition to a number of books and publications that detail balanced pruning methodology, principles, and philosophy, there exists an extensive online reservoir of material that can be easily accessed for guidance related to pruning. More detailed explanations and even experiment findings related to pruning can be found in the Wine Grape Production Guide for Eastern North America, The Grapevine: From the Science to the Practice of Growing Vines for Wine, Sunlight Into Wine, and myriad other texts.

Many cooperative extension services (Penn State University, Washington State University, Cornell University, etc.) can be particularly helpful with providing information about pruning, and instructional presentations and in-field videos can easily be found online through a simple web-based browser search or through the aforementioned universities’ cooperative extension websites.


Literature Cited

Iland, P., P. Dry, and T. Proffitt. 2011. The grapevine: From the science to the practice of growing vines for wine. Patrick Iland Wine Promotions Pty Ltd, Adelaide, Australia.

Jordan, T.D., R.M. Pool, T.J. Zabadal, and J.P. Tomkins. 1966. Cultural practices for commercial vineyards. Miscellaneous Bulletin 111. Cornell University, Ithaca, NY.

Reynolds, A.G., and T.K. Wolf. 2008. Pruning and training. In Wine Grape Production Guide for Eastern North America. Tony K. Wolf (ed.), pp. 98-109. NRAES, Ithaca, NY.

Willwerth, D., K. Ker, and D. Inglis. 2014. Best management practices for reducing winter injury in grapevines. Cool Climate Oenology & Viticulture Institute, Brock University, Ontario, Canada.


Andrew Harner is a graduate student at Penn State, where he is pursuing a MS degree as a member of the Plant Science Department and studying how climatic and environmental factors influence rotundone synthesis and concentration in Noiret wine grapes with Dr. Michela Centinari. He is currently funded by the John H. and Timothy R. Crouch Program Support Endowment, an endowment founded and funded by the Crouch brothers, original owners of Allegro Winery in Brogue, PA. Drew graduated from Cornell University in 2016, where he focused his studies on Horticulture and Viticulture/Enology and was first introduced to the world of grapevines and plant-based research. Following the conclusion of his MS program he hopes to continue onwards within academia and pursue a PhD, and spends much of his free time either reading, cooking, or outside exploring the natural areas and parks of the U.S.

Reviewing YAN and Hydrogen Sulfide: Part 2

By: Denise M. Gardner

In a previous post, we discussed ways in which nutrient management during primary fermentation can affect hydrogen sulfide formation and the overall “health” of the wine.  This week, we’re going to explore how to mediate hydrogen sulfide aromas and flavors in a finished wine.

Sulfur-Containing Off Aromas

In general, many wine sensory scientists and wine experts will agree that is relatively a bad habit to use the term “sulfur” to describe off-odors associated with hydrogen sulfide or “stinky” aromas that are usually described by the term “reduced.”  One of the main arguments for avoiding “sulfur” as a description term for an aroma is due to the fact that there are actually several forms of aromatic sulfur-containing compounds found in wine, and they can have very different aromas (smells, odors) associated with that one compound.  The most common groups of aromatic sulfur-containing compounds in wine are:

  • Sulfur dioxide (SO2)
  • Hydrogen sulfide (H2S)
  • Mercaptans or Thiols
  • Disulfides

Additionally, many sensory experts will advise further to avoid using the chemical names as descriptors for describing an aroma found in wine (e.g., using the term “hydrogen sulfide” to describe the hard-boiled or rotten egg aroma).  It is typically recommended to use an actual descriptor when describing an aroma (e.g., using the term “rotten eggs” when that smell exists in wine).

Sulfur Dioxide (SO2)

Sulfur dioxide is an antioxidant and antimicrobial preservative frequently used in wine production.  However, it is also produced by yeast during primary fermentation, which is why wines (and other fermented products) cannot be sulfur dioxide-free (commonly referred to as “sulfite free” in the mass media).  The aromatic descriptor commonly associated with a high concentration of sulfur dioxide is termed “burned match,” but a high concentration of sulfur dioxide can also cause a nasal irritation that many will describe as nasal burning.  For more information on sulfur dioxide and managing its concentration in wine, please refer to this Wine Made Easy Fact Sheet produced by Penn State Extension.

Hydrogen Sulfide (H2S)

Hydrogen sulfide is an aromatic compound that is commonly described as having a “rotten egg” or “hard-boiled egg” aroma.  Like many sulfur-containing compounds, hydrogen sulfide has a low sensory threshold (<1 – 1 part per billion, ppb), indicating that about 50% of the population could sense this compound at that concentration without being able to identify it, specifically, as hydrogen sulfide.

As we saw in our previous post, hydrogen sulfide development can result as a component of poor nutrient management during primary fermentation.  Residual elemental sulfur from pesticide sprays has also been linked to latent development of hydrogen sulfide in wines.  In a 2016 edition of Appellation Cornell, Dr. Gavin Saks’ lab provided a detailed and practical report on how hydrogen sulfide can be a problem for winemakers post-bottling and the potential links to hydrogen sulfide development as a function of residual sulfur from the vineyard (Jastrzembski and Saks, 2016).

Occasionally, winemakers may also experience hydrogen sulfide formation during a sur lie aging period; a time in which the finished wine remains on the lees when lees are stirred in the wine.  It is also common for sparkling wines, produced in the traditional method, to exhibit a small perception of hydrogen sulfide when the bottle is first opened.

Mercaptans/Thiols and Disulfides

Finally, mercaptans or thiols, sulfur-containing compounds that contain the functional group –SH, and disulfides, sulfur-containing compounds that contain a S-S bond, can also be problematic for winemakers when found at high concentrations.

The presence of sulfur-containing volatile compounds is not always considered detrimental to wine quality.  For some wine grape varieties (e.g., Sauvignon Blanc), these classes of compounds can make up their varietal aroma.  In very small concentrations, sulfur-containing compounds can also be aroma enhancers, indicating that their presence can actually make the wine smell fruitier than if they were not present in the wine.  However, when at substantial concentrations, volatile sulfur-containing compounds can also produce various “stink” aromas that mask a wine’s fruitiness, freshness, and make the wine generally unappealing.  This is phenomena is dependent on the concentration of the sulfur-containing compound and the chemical makeup of the solution (i.e., wine) it is in.

Mercaptans or thiols and disulfides have a variety of descriptors associated with them, and their perception is largely based on concentration.  When we’re discussing the negatively-associated descriptors, common terms include: garlic, onion, canned asparagus, canned corn, cooked cabbage, putrefaction, burnt rubber, natural gas, and molasses amongst others.

Are There Sulfur-Containing Off-Aromas in Your Wine?

To identify if hydrogen sulfide, mercaptans/thiols, or disulfide-based off-odors exist in your wine, it may be best to use a copper screen as a bench trial.  While analytical identification of these compounds is possible, it is often expensive and leaves the winemaker guessing on what to do next.

For a quick assessment of a wine’s aroma, winemakers can drop 1-2 pre-1985 copper pennies into a glass of wine to see if the aroma freshens.  The freshening aroma is due to the fact that the copper from the penny is reacting with the sulfur-containing compounds in the wine and making them aromatically inactive.

The "penny test" is often used to quickly determine if a wine is suffering from reduction, the presence of several types sulfur-containing off-odors. Photo by: Denise M. Gardner

The “penny test” is often used to quickly determine if a wine is suffering from reduction, the presence of several types sulfur-containing off-odors. Photo by: Denise M. Gardner

A technical copper screen takes a bit more work and should be conducted in a quiet and aromatically-neutral environment.  It is recommended to do this outside of the cellar.

Copper addition, in the form of copper sulfate, is often used to remediate aromas/flavors associated with hydrogen sulfide. One-percent and 10% copper sulfate solutions can be purchased through your local wine supplier.  The basic protocol associated with a copper screen is as follows:

  1. Add 50 milliliters of wine to two glasses.
  2. Label one glass “control” and the other “copper addition” (see image below).
  3. Add 1 mL of 1% copper sulfate to the “copper addition” glass.
  4. Cap both glasses for 15 minutes.  Sniff the aroma of each wine.
Setting up a copper screen can help determine if a wine is suffering from aromas caused by sulfur-containing compounds. Photo by: Denise M. Gardner

Setting up a copper screen can help determine if a wine is suffering from aromas caused by sulfur-containing compounds. Photo by: Denise M. Gardner

Sniff (smell only!) both glasses. Most people start with the “control” and smell the treated wine (wine containing copper sulfate) second.  If the aroma/flavor of the “copper addition” glass has improved, or the hydrogen sulfide aroma has subsided, then a copper addition trial should follow to determine the exact concentration of hydrogen sulfide needed to clean up the wine in question.  Remember that the legal limit for copper allowed in a finished wine is 0.5 ppm.  For a full protocol on how to run a copper addition bench trial, please refer to this Penn State Extension Wine Made Easy Fact Sheet.

Treatment of Sulfur-Containing Compound Off-Aromas

Sulfur-containing compounds are quite reactive, which can make dealing with them fairly difficult.  Many educators agree that the best way to treat sulfur-containing compounds, especially those that stink, is to prevent their existence as best as possible.

In the Appellation Cornell newsletter that focused on sulfur pesticide residues, Jastrzembski and Saks (2016) recommended that sulfur residue concentrations should not exceed 1 mg/kg at harvest in order to avoid latent hydrogen sulfide or sulfur-containing off-aromas later in processing and storage.  Additionally, many experts recommend appropriately treating fermenting musts with nutrient management strategies based on the starting YAN concentration to minimize the incidence of hydrogen sulfide formation during primary fermentation.  This topic was covered in a previous blog post.

As described above, winemakers may also opt to treat the wine with copper sulfate to try to reduce the perception of hydrogen sulfide or other sulfur-containing aromas.  It should be noted that aromas caused by disulfides cannot be mediated with a copper sulfate addition.

There has been more conversation in the academic community regarding the reemergence of hydrogen sulfide or sulfur-containing off-aromas after a wine has been treated with copper and post-bottling.   The theory around this appears to circulate around residual copper initiating reactions in the wine that lead to more sulfur-containing off-odors.  This continues to be an ongoing discussion amongst researchers and will likely be a hot topic within with the wine industry.  For now, it is important for winemakers to understand that there may be a risk of off-odors reemerging post-copper treatment and post-bottling.  This topic will also be discussed to some degree at the 2017 PA Wine Marketing and Research Board Symposium on March 29, 2017 in State College, PA, and winemakers are encouraged to attend.

Some hydrogen sulfide or sulfur-containing off-odors can sometimes be mediated with use of fresh lees stirred in the wine or the addition yeast lees-like products.  Winemaking products like Lallemand’s Reduless, yeast hulls, or some cellulose-based products can help reduce or eliminate the intensity of these off-odors.  As with any other product additions, it is recommended that wineries always do bench trials first and before adding to the entire volume of wine.  Additionally, Enartis USA (Vinquiry) has previously distributed a fact sheet to help winemakers troubleshoot reduced wines and determine how to best treat a problem wine.


The incidence of reduction, sulfur-containing off-odors, or hydrogen sulfide can be a frustrating circumstance for winemakers.  However, adequate vineyard care and proper nutrient management during primary fermentation can help minimize the incidence rate of sulfur-containing off-odors from occurring in their wines.  Of course, problems with wines do occur, and we hope that the recommendations above will help winemakers solve wine problems pertaining to sulfur-containing off-odors.



Jastrzembski, J. and G. Sacks. 2016. Sulfur Residues and Post-Bottling Formation of Hydrogen Sulfide. Appellation Cornell, 3a.

What Drives Mid-Atlantic Wine Consumers’ to Visit Local Winery Tasting Rooms

By Jennifer Zelinskie and Dr. Kathy Kelley

Whether you work in the wine industry or are just a wine consumer who reads the Wine & Grape U. Blog, you have probably visited many different winery tasting rooms. Reflecting on these visits, you probably remember instances when you had an exceptionally good experience and times when your visit might not have been all that delightful. We are pretty sure that you made the decision to return to the facility while tasting the wines or just after the door shut upon your exit.

If you are a winery tasting room owner or operator, you want all of your customers to have a memorable positive experience and have no doubt that they will visit again. This blog post presents data collected from our Mid-Atlantic wine consumer participants as to what had a positive influence on their willingness to visit again.

The Impact of Customer satisfaction

Customer satisfaction is critical to the success of any business. Miguel Gomez, a faculty member at Cornell University, shared five factors that drive customer satisfaction, builds loyalty, and encourages repeat winery tasting room visits. These include:

  • ambience – cleanliness, ambiance, lighting, sounds, view, etc.;
  • service – staff friendliness, knowledge, appropriate appearance, and helpfulness;
  • tasting protocol – variety, amount served, cost, and number of wines tasted;
  • tasting experience – flexibility in choice of wines, space (crowdedness), waiting time to start and between samples; and
  • retail execution – presentation of wine for purchase, quality, prices, discounts, and ease of locating the winery (http://bit.ly/2jy3v2C).

According to data collected as part of the Northern Grapes Project, funded by the USDA, the average number of bottles study participants purchased increased as customer satisfaction increased. Participants were asked to rate their “level of customer satisfaction” in tasting rooms on a scale of 1 (lowest level of customer satisfaction) to 5 (highest level). Participants that rated their tasting room satisfaction level a ‘4’ out of ‘5’ purchased an average of 2.8 bottles of wine, but those who rated their tasting room satisfaction level a ‘5’ out of ‘5’ purchased an average of 4 bottles (http://bit.ly/2k5gG7L). Average amount of money spent at the tasting room also increased as level of customer satisfaction increased. Those who awarded ratings of ‘4’ out of ‘5’ spent an average of $40 and those who awarded ratings of ‘5’ out of ‘5’ spent an average of $60.

How far did our participants travel to winery tasting rooms during an average year?

In our March 2016 survey, participants were asked if they visited and/or purchased wines from winery tasting rooms that were located within 100 miles from their home during an average year. Of the 1,038 participants, 505 (50.1%) responded “yes.” These 505 participants were then asked a series of questions regarding their winery tasting room visits.

Why might purchasing wine from a tasting room be more appealing than purchasing wine from a retail liquor store?

As a winery tasting room owner you want your customers to come and visit your location, taste your wine, and make purchases on a regular basis. Yet one of your major competitors is the local liquor store, which can be more convenient (e.g., hours of operation) for consumers and provide them with a greater selection of wines (e.g., type, origin, price) than you offer.

Hence we asked our participants who visited winery tasting rooms within 100 miles of their home to react to factors that may have influenced them (positively and negatively) to travel to a tasting room, rather than a liquor store, for a visit and/or to purchase wine. Data presented below (Figures 1 through 3) are for the 95.6% of participants who indicated that at least one factor influenced them in a positive way to travel to a winery tasting room to visit and/or make a purchase. We will discuss factors that had a negative influence in another blog post.

Factors that Had a Positive Influence on Participants’ Visits and/or Purchases

As you can see in Figure 1, below, nearly half of the 505 participants selected “prefer to purchase directly from the winemaker” (48.6%) and that “purchasing wine directly from the winery tasting room provides more support to the local economy” (47.9%) as having a positive influence on why they traveled to a tasting room within 100 miles of their home to make a visit and/or purchase wine, as opposed to a retail liquor store. We chose the 100-mile distance as 64% of participants in one study responded that for a food to be “local” it had to be produced within a 100-mile radius “of the store” (http://bit.ly/2jxi1VO), and there are reasons why you might promote your tasting room as being a local wine source.


Individuals who buy wine from local wineries may do so because they feel a sense of community when they make the purchase. Others may purchase local because of economic benefits. For example, when $100 is spent at a local business “roughly” $68 stays in the community while only $43 “stays in the local economy” when $100 is spent at a non-locally owned business (http://bit.ly/12cRrXn). Or, they may feel that local foods and local wines are a natural pairing. According to David Page of Shinn Estate Vineyards, though it may take decades or longer, “the wine of a region and the food of a region creates the cuisine of the region” (http://nyti.ms/2kcdVBt).

How can you, as a winery tasting room owner or operator, use the “buy local” trend to engage your customers?

  • Promote your business as being local, that you make your wine locally, and/or that the grapes and other ingredients used in the wine are from local sources. The Hive Winery, located in Layton, Utah, states on their website that their “wines are crafted using fruit and home from local farms as much as possible” (http://bit.ly/2kwO47H). If you look through their website you will learn that the local theme is not just mentioned once, but they discuss why consumers may want to buy local, indicate the ingredients in each wine that were sourced locally (e.g. “11 pounds of fresh Utah black cherries [are used] per bottle” of their Black Cherry Brandy, http://bit.ly/2kx2K6F), and link to other local businesses. Discussing why local, as well as other environmental practices, is important to them helps convey to readers that they are not merely using “local” just to drive sales.
  • Find a “buy local” association, build a relationship with other local businesses, and work together to promote your businesses and the community. In 2013, 14% of independent businesses located in Michigan “Local First” communities indicated that the effort had a “significant positive impact” on their business, 28% reported a “moderate positive impact,” and 33% “a little positive impact” (http://bit.ly/1gcOesa). These businesses reported a greater percent change in revenue in 2013 over 2012, a 7.0% increase compared to 2.3% for independent businesses in communities without a Local First initiative, and a greater positive change in 2013 holiday sales compared to 2012 (http://bit.ly/1gcOesa).
  • Register your business as a “Small Business Saturday” participant (http://amex.co/1JdleC6). This campaign, hosted by American Express, is held on a Saturday after Thanksgiving and encourage shoppers to buy from local businesses. Now approaching its eighth year, 112 million consumers shopped and dined at small businesses on Small Business Saturday 2016, a 13% increase over 2015 (http://bit.ly/2koxVRI). Not only do consumers focus on purchasing from small businesses on this shopping holiday, but 77% of consumers who participated in 2014 survey responded that “the day makes them want to shop local year-round” (http://bit.ly/2jxFO7q). One winery that utilizes Small Business Saturday is North Folk Winery, Harris, MN. Thewineyhosted a wine pairing with local cheese and chocolate and offered attendees a 20% discount on bottles when they purchased cheese and chocolate gift boxes (http://bit.ly/2jxdAKH).

Offering discounts in your winery tasting room can help attract new customers, encourage undecided customers to make a purchase, and prompt those who have not visited your tasting room in a while to stop in and see what is new.

Pertaining to discounts and programs that would provide incentives for purchasing multiple bottles, 40.1% of our participants indicated that such a discount had a positive influence on their decision to travel to tasting rooms, as opposed to a retail liquor store (Figure 2).


Ron Lykins, a wine tasting room associate, suggests in a blog post that offering a discount on purchasing multiple bottles of wine is a reasonable strategy and encourages up-selling. He provides an example where a customer is purchasing four bottles of wine and is then presented with a modest discount if the customer purchases an additional two bottles.  He stresses that the policy needs to be clearly defined and that all tasting room staff must know when it should be offered (http://bit.ly/2j9BLhe).

But why do discounts work in attracting customers to your tasting room?

 The psychology behind discounts is to create urgency. Which can be achieved by:

  • Using phrases such as “get $10 off your case purchase” or “get 5% off a case purchase,” which specify what is actually being discounted, are more likely to motivate people to buy compared to using less direct statements like “save $10” or “save 10%.”
  • Limit the amount of time you offer the discount, preferably no more than a couple of weeks to encourage customers to buy before it is too late.
  • Inform customers about the discounts when they are if your tasting room and through all modes of communication (http://bit.ly/2jA0Cho).

Of the 505 participants who visited and/or purchased wines from winery tasting rooms that were located within 100 miles from their home during an average year, few participants (14.7%) indicated that being a member of the winery’s wine club and earning rewards by making purchases was a positive influence. This low response may be due to the fact that only 20.8% of these 505 participants reported being a club member or subscriber.

Although this is the case for our survey, as a winery owner or operator, you have the ability to customize your reward system and offer benefits that motivate your customers to become members and renew annually. Keep in mind that it is not just the discount that encourages customers to join a wine club, but there are also “intangible” benefits. You have the opportunity to make your club members feel special, whether that means hosting private events or getting to know them by name (http://bit.ly/2j9BLhe), both of which help members feel truly connected with the winery and tasting room staff. You can read more about our participants’ interest in wine club membership benefits by clicking here: http://bit.ly/2iCoulc.

Whether you are offering discounts to all customers or just members of your wine club, consider the following to make sure that your discount does not have a negative impact on your business:

  • Calculate the best discount price that will still generate a profit by understanding your gross margin, markup, and breakeven figures.
  • Know that you will need to increase your sales volume, which differs based on the discount offered, in order to maintain the desired gross margin. According to the example on the Business Victoria website (http://bit.ly/2jIa96k), if your gross margin is 40% and you offer a 5% discount then you will need to “increase your sales volume by 14.3 percent in order to make a profit.” If you change that 5% discount to a 10% discount you will need to increase your sales volume by 33.3%.
  • Become familiar with what discounts other winery tasting rooms in your area are offering. Though your operations may not be identical, this can at least give you some guidance as to what type of discount you might offer, amount of discount to provide, and frequency which to offer the discount.
  • Review last year’s sales and identify times (days of the week, seasons, etc.) when your sales were low and that, perhaps, running discounts during these times could increase foot traffic and boost sales (http://bit.ly/2jIa96k).

Figure 3 shows survey participant responses to the remaining three factors that could have a positive influence on their likelihood to travel to a winery tasting room, as opposed to a retail liquor store, within 100 miles of their home. Over half, 56.6%, of participants indicated that they like to be able to taste all or most of the wine before making any purchases. Half (51.0%) indicated that they like the taste and/or quality of the wine they purchase directly from the winemaker and approximately a third (31.2%) reported that being able to buy wines made with grapes native to their area (e.g., Niagara, Catawba) were reasons why they traveled to the tasting room.

screenshot-2017-01-26-10-42-48You know how wine tastings influence your visitors’ purchasing decisions, and that if you can get a reluctant visitor to try a wine that they are unfamiliar with – you might just get a sale. Whether you currently make wines that are less known or are contemplating doing so, you should consider encouraging as many visitors as possible to sample them.

In 2012, Michigan State University researchers investigated consumer awareness and perceptions of cold hardy grape wines (e.g., Brianna, Edelweiss, La Crescent, Marquette). According to their results, slightly more than half (55.5%) of Michigan tasting room visitors responded that they were not familiar with cold hardy wines, while 65.3% indicated that they had tasted them. An additional mail/email survey was implemented in six Mid-Western states. Awareness was even lower among these wine consumers, with 70% responding that they were not familiar with the wines and only 26.8% responding that they had tasted the wines (http://bit.ly/2jKwLC).

Although awareness of cold hardy wines was low, consumers who had tasted cold hardy grape wine reported to like them “a lot” (41.9% of the MI tasting room visitors and 39.3% of mail/email survey participants) or “a little” (29.9% of the MI tasting room visitors and 31.1% of mail/email survey participants; http://bit.ly/2jKwLC).

Educating your staff about these wines and guiding them as to how they can encourage customers to taste “unknown” or “less familiar” wine is crucial.

Of note….

We recognize that percentages of respondents who indicated that these factors had a positive influence on their winery tasting room visits were not as high as might have been expected. None of the percentages were greater than 56.6%. In the future, we plan to investigate other factors that may have a positive influence on winey tasting room visits.



Reviewing YAN and Hydrogen Sulfide: Part 1

By: Denise M. Gardner

Yeast assimilible nitrogen (YAN) is the sum of the amino acid and ammonium concentrations available in the grape juice at the start of fermentation.  Typically, the amino acid proline is not included in the reported amino acid content as it is not readily utilizable by yeast cells.

The amino acid component of YAN is often referred to as the “organic” YAN form.  In contrast, the ammonium ion content is referred to as the “inorganic” YAN form and may be written in its ionic abbreviation: NH4+.  Due to the fact that ammonium is only connected to a series of protons (H+ ions), it tends to be easier to move in and throughout the yeast cell to be consumed during fermentation (Mansfield, 2014). When these two components (organic + inorganic) are added together, the resultant value is the YAN, written with the units: mg N/L.

The winemaking challenge associated with YAN is the fact that it is quite variable, and current research has not identified ways to change the YAN, predictively, in fruit through the manipulation of vineyard practices.  YAN varies by vintage year, grape variety, cultivar, and with the use of various vineyard management practices.  In Penn State’s research vineyards, ~1 acre in size and containing 20 different wine grape varieties, YAN values ranged dramatically each vintage year amongst the various wine grape varieties.  On any given vintage year YAN values ranged from low (<100 mg N/L) to high (>300 mg N/L) amongst the varieties grown in that one site.

The variability associated with YAN provides a secondary challenge to winemakers: the lack of predictability associated with hydrogen sulfide formation during primary fermentation due to unfulfilled nitrogen needs by wine yeasts.

What does YAN have to do with Hydrogen Sulfide?

Winemakers often talk about YAN in relation to hydrogen sulfide (H2S) as the two have been associated with one another throughout primary fermentation.  Although there are several potential causes of hydrogen sulfide formation during wine production, some of which we will talk about in our Part 2 series, nitrogen imbalance has been one of the factors that winemakers can influence through production.  Unfortunately, there is no way to ensure that a wine will not produce hydrogen sulfide by the end of fermentation, but treating wines with proper nutrient supplementation can help minimize the incidence of hydrogen sulfide production during primary fermentation.

Hydrogen sulfide is produced by the yeast cell via the sulfate reduction pathway (Figure 1).  While I know this figure looks scientifically daunting, we can try to simplify its purpose to discuss how hydrogen sulfide is released into wine.  Sulfate (SO42-), naturally abundant in grape juice (Eschenbruch 1974), is transported into the yeast cell for amino acid (cysteine and methionine) development, which are naturally lacking in concentration in grape juice (Bell and Henschke, 2005).  Energy is used by the yeast (represented as ATP in Figure 1) to chemically alter the structure of sulfate in order to make it useable by the yeast cell.  This useable form can be seen as sulfide (S2-) in the image below.  Using nitrogen, which is required to make an amino acid, the sulfide content is depleted as cysteine and methionine amino acids get produced.  Therefore, as sulfide reserves are depleted, cysteine and methionine contents generally increase to be used for building proteins that will be needed by the existing or new yeast cells.

Figure 1: A simplified version of the sulfate reduction pathway.

Figure 1: A simplified version of the sulfate reduction pathway.

Sulfur dioxide (SO2) plays a role in the sulfate reduction pathway in that it bypasses the transport mechanism required to bring sulfur into the yeast cell.  It other words, it can diffuse across the cell membrane and into the internal parts of the yeast cell.  Sulfur dioxide will get chemically altered to be made into the useable sulfide , S2-, form as well.  Therefore, fermentations that contain a high concentration of sulfur dioxide at the start of fermentation have the potential to increase the utilization of sulfur dioxide during yeast metabolism.

These processes function normally until a depletion of nitrogen (from the nitrogen pool) or an accumulation of sulfide develops in the yeast cell.

If there is not enough nitrogen (low YAN fermentations) available to make the sulfur-containing amino acids (cysteine and methionine) then, eventually, the yeast cell will not be able to continue manufacturing these amino acids.  In this situation, the sulfide concentration generally starts to increase within the yeast cell.

The chemical form sulfide, however, is toxic to the yeast cell and thus, the yeast will try to eliminate it from its internal structures.  Therefore, when sulfide concentrations get too high, the yeast will diffuse this across its cell membrane into the surrounding media: the fermenting juice.  When hydrogen sulfide concentrations get high enough in the fermenting juice, winemakers can often sense the rotten or hardboiled egg aroma associated with the compound.

What if there is too much nitrogen?

In contrast, too much nitrogen (high YAN fermentations) can also be problematic.  Higher concentrations of the inorganic component of YAN can lead to a high initial biomass (population) of yeast.  The rapid increase in yeast populations can lead to nutrient starvation by a majority of the yeast when the wine is about almost finished completing fermentation.  With a large biomass of yeast incapable of obtaining the proper nutrient (nitrogen) content to grow and reproduce, hydrogen sulfide development can result.  This is due to the fact that there is a large population of yeast in situations in which there is not enough nitrogen to support their growth (i.e., there is not a lot of food to go around for all of the yeast cells).  With hydrogen sulfide development occurring late in primary fermentation, it is obvious that the winemaker would become concerned with hydrogen sulfide retention by the time fermentation is fully complete.

Too much nitrogen can also cause other quality problems.  Due to the excess amount of available nutrients, yeast can grow and reproduce quickly, which often leads to very rapid or very hot fermentations.  The speed of fermentation, of course, can affect the aromatics and quality of the wine (i.e., fast fermentations often lead to simpler aroma and flavor profiles).  This may not be an issue with some styles of wine, but for many white wine or fruit (other than grapes)-based fermentations, aromatic retention is often a priority by the winemaker.

Due to the fact the initial YAN is so high, all of the nitrogen contents may not be utilized by the yeast population by the end of fermentation, and could remain in suspension in the finished wine.  As yeasts begin to autolyze, all of their inner components, including the remaining nitrogen content, will become available in the wine.  The excess “food” could be available for other microorganisms (like acetic acid bacteria, lactic acid bacteria, or Brettanomyces), which could potentially lead to spoilage problems if the wine is not properly stabilized.  Such spoilage is, obviously, detrimental to wine quality and undesirable by the winemaker.  Alternatively, remaining nutrients could be utilized by malolactic bacteria or those wines that will be given tirage for sparkling production (Bell and Henschke, 2005).

Finally, higher YAN concentrations can lead to an increased risk of ethyl carbamate production in wine; ethyl carbamate is a known carcinogen that can give susceptible individuals headaches, or even respiratory illness.  Ethyl carbamate is produced in a reaction between ethanol and urea (Bell and Henschke, 2005).  The heavy use of DAP has also been linked to a higher potential risks of ethyl carbamate due to the fact that DAP inhibits the transport of amino acids into the yeast cells, and therefore, leaves a higher concentration of amino acids available that can potentially be altered into urea, a precursor for ethyl carbamate (Bell and Henschke, 2005).

The fact that excess nitrogen can be problematic during wine production should provide insight to winemakers to avoid over-supplementing their fermentations.  Hence, it is often recommended to that winemakers measure and identify their starting concentration of YAN and supplement accordingly.

Nitrogen Supplementation

Nitrogen (nutrient) management and supplementation is not uncommon during primary fermentation as nutrients are an important component of yeast cell growth and metabolism.  In the yeast cell, nitrogen is a required nutrient in the synthesis of amino acids and to build proteins that are used in the yeast cell walls and organelles, as discussed above.  Without protein development, the yeast cell cannot live.

Winemakers can supplement their fermentations with nitrogen by adding nutrient supplements in the form of:

  • Hydration nutrients (e.g., GoFerm, Nutriferm)
  • Complex nutrients (e.g., Fermaid K, Nutriferm)
  • Diammonium phosphate (DAP)

DAP is considered an inorganic form of nitrogen, while the complex nutrients may contain additional organic yeast components that contribute organic forms of nitrogen.  Recall, above, that the inorganic form of nitrogen is more readily consumed by yeast, and it can be easily absorbed by yeast cells even as alcohol concentrations rise during primary fermentation.  Amino acids, on the other hand, require energy expenditure in order to be brought into the cell through transport proteins located on the cell membrane.  The presence of both alcohol and ammonium ions inhibit the transfer of amino acids from the juice into the yeast cell (Santos, 2014).  Therefore, it is often recommended to avoid the addition DAP or products that contain DAP (i.e., Fermaid K, Nutriferm Advance) at inoculation and until after yeasts have the opportunity to best absorb amino acids.  If you are looking for some guidance on when to add nutrients to your fermentation, please refer to our Wine Made Easy fact sheet on the Penn State Extension website.

Starting YAN Concentrations

Nonetheless, nutrient supplementation strategies are often based on starting YAN concentrations in the fruit.  Due to the regular variability of YAN concentrations, winemakers are encouraged to measure YAN for each lot of grapes every year.  This is often problematic for winemakers whom do not have the time to run the appropriate analyses associated with YAN or the financial resources to send samples to an analytical lab.  Such challenges force many winemakers into a situation in which all fermentation lots are treated with the same repeated nutrient supplementation regardless of the starting concentration of YAN.

In previous Extension workshops, research from Cornell University on Riesling wine grapes found that they could accurately predict the harvest YAN when good field samples were taken within 2 weeks from harvest (Nisbet et al., 2013).  In 2016, Cornell released a second publication that focused on YAN prediction models for Cabernet Franc, Chardonnay, Merlot, Noiret, Pinot Noir, Riesling, and Traminette.  While the prediction models were not recommended for regions outside of the Finger Lakes (where the data was sourced from for this study), they found that in some cases, YAN data could be obtained within 5 weeks of harvest (Nisbet et al., 2014).  This extra flexibility in time can aid in obtaining accurate YAN results before the grapes reach the crush pad, which ultimately helps winemakers prepare for nutrient supplementation before the start of fermentation.

Until further research can provide predictive modeling for other wine regions, it is generally accepted that winemakers should measure YAN at or as close to harvest as possible.

YAN can be measured using the following the analytical procedures:

  • Enzymatic methods for both primary amino acids and ammonium.
  • Probe for ammonium ions.
  • Formol titration

While the Formol titration is often preferred by many small wineries due to the lower start-up investment, the use of formaldehyde, a known carcinogen and lung irritant, in this protocol does require some consideration for laboratory safety.  Additionally, the proper disposal of formaldehyde, a hazardous substance, can be an issue for many wineries.

Enzymatic methods by spectrophotometer definitely require a bit of experience in order to become more efficient in their use, which can be problematic for those operations that find measuring YAN too timely.  Additionally, enzymatic kits have to be purchased fresh and have a small shelf life.  The advantage of investing in a spectrophotometer, however, is that other enzymatic kits can be purchased to measure additional wine components including residual sugar, malic acid, and acetic acid.

Nonetheless, measuring YAN should be a consideration for wineries that struggle with hydrogen sulfide aromas by the end of primary fermentation.  It is through the starting numerical value that winemakers can better manage and adjust nutrient supplementation strategies to help minimize the reoccurrence of hydrogen sulfide at the end of fermentation.


Nutrient availability during primary fermentation is only one potential contributor to hydrogen sulfide formation in wines.  In the next blog post, we’ll explore other potential causes of hydrogen sulfide formation and how to best mediate the problem when it exists.



Eschenbruch. R. 1974. Sulfite and sulfide formation during winemaking – a review. Am. J. Enol. Vitic. 25(3): 157-161.

Bell, S.-J. and P.A. Henschke. 2005. Implications of nitrogen nutrition for grapes, fermentation and wine. Aust. J. Grape and Wine Res. 11:242-295.

Mansfield, A.K. Are you feeding your yeast?: The importance of YAN in healthy fermentation. Webinar. Feb. 2014.

Nisbet, M.A., T.E. Martinson, and A.K. Mansfield. 2013. Preharvest prediction of yeast assimilable nitrogen in Finger Lakes Riesling using linear and multivariate modeling. Am. J. Enol. Vitic. 64(4): 485-494.

Nisbet, M.A., T.E. Martinson, and A.K. Mansfield. 2014. Accumulation and prediction of yeast assimilible nitrogen in New York winegrape cultivars. Am. J. Enol. Vitic. 65(3): 325-332.

Santos, J. Getting Ready for Harvest: Yeast Nutritional Needs. Workshop Seminar. July 2014.

Harvesting the Knowledge Accumulated at Penn State on Grapes and Wine

By: Denise M. Gardner

Early in 2016, I was asked to create a “behind the scenes” event in late October to feature our research winemaking program and share this with alumni to introduce them to some of the things that Penn State offers in the fields of viticulture and enology.  This was, by far, one of the most interesting events I have organized during my time with Penn State, and it ended up being a very rewarding experience, personally, to see the pride and talent that contributed to make the event a success.

The challenge: teach a group of adults about wine production… most of whom have probably very little knowledge about or experience in actual wine production.

As many of us know, making wine is not really the romantic ideal that is often portrayed and associated with the wine industry.  We all know that we aren’t overlooking our vineyards with a glass of wine in hand 24-7.

It’s hard work.  It’s dedication.  And it’s farming.

When I introduced this event idea to the Extension Enology Advisory Committee – a group composed of 13 volunteers from Pennsylvania’s wine industry and several representatives from various academic communities – they all jumped on the idea of showcasing the Penn State Extension Enology presence and the impact it has had on the local industry in addition to Penn State’s research programs.

Starting in April 2016, I went to work on developing a short [film] script to organize and develop a small video that highlighted our research initiatives and student involvement around winemaking at Penn State.  The hope was that this video would feature how students, faculty, and staff are getting involved with industry members via Penn State Extension’s programs while also explaining how wine is generally produced.

With this video, I ended up interviewing two faculty members from our research team, Dr. Michela Centinari from the Dept. of Plant Sciences and Dr. Ryan Elias from the Dept. of Food Science.  We collected their perspectives and opinions on various activities that they have been involved in and related it back to the growth and development associated with Penn State offering educational and research experiences in viticulture, enology, and wine marketing.

Figure 1: Filming Day! Dr. Ryan Elias, Dr. Michela Centinari, and Denise Gardner get interviewed and video taped for a small presentation on winemaking at Penn State. Filming completed by media guru, Jon Cofer. Photo by: Denise M. Gardner

Figure 1: Filming Day! Dr. Ryan Elias, Dr. Michela Centinari, and Denise Gardner get interviewed and video taped for a small presentation on winemaking at Penn State. Filming completed by media guru, Jon Cofer. Photo by: Denise M. Gardner

Luckily, one of the media specialists within the College of Agricultural Sciences, Jon Cofer, had a collection of footage that we had shot during wine processing days just in case we ever needed video footage for anything.  As luck would have it, we did need the media footage!  Jon sifted through hours of film to find the best footage, which we then tied back into the explanation on how research wines are generally processed at Penn State.

During our travels around the state, whether it was to check in on research trials or visit with industry members during Regional Winery Visits, Michela, a group of dedicated graduate students, and I collected video footage in commercial vineyards in an attempt to highlight what goes on during the growing season.  And finally, I met with some recent graduates that experienced educational opportunities through Penn State and Extension, and who both work in Pennsylvania’s wine industry today.  I have to admit, one of the most awarding experiences in being Penn State’s Extension Enologist is that I have watched several “students” graduate and find full-time job placement within our state’s wine industry.  It is an absolute joy to see these young adults exceed in a growing industry.

The result of this event couldn’t have been better received.  Instead of making wine with a group of non-winemakers, we set up three educational stations to teach about:

  1. wine grape properties and vineyard management by highlighting how to conduct a berry sensory analysis, explaining berry physiological differences, and teaching how to read a refractometer.
  2. the chemistry behind fermentation and sensory training associated with wine tasting through analytical demonstrations and “aroma guessing” with aroma standards.
  3. and evaluating the end result (finished wine!) of some of our best research wines and commercial winery collaborators.
Figure 2: Graduate students, Maria and Drew, get ready to teach attendees about wine grape properties. Maria and Drew are members of Dr. Michela Centinari's research lab. Photo by: Tom Dimick

Figure 2: Graduate students, Maria and Drew, get ready to teach attendees about wine grape properties. Maria and Drew are members of Dr. Michela Centinari’s research lab. Photo by: Tom Dimick


Figure 3: Jared Smith (Dept. of Food Science Teaching Lab Support Specialist and previous graduate supported by the Crouch Endowment) explains how winemakers monitor fermentation and the use of temperature-controlled fermentation tanks. Photo by: Tom Dimick

Figure 3: Jared Smith (Dept. of Food Science Teaching Lab Support Specialist and previous graduate supported by the Crouch Endowment) explains how winemakers monitor fermentation and the use of temperature-controlled fermentation tanks. Photo by: Tom Dimick


Figure 4: Graduate student, Laurel, tests attendees on their ability to smell and aroma and guess what it is. Laurel works within Dr. Ryan Elias's lab. Photo by: Tom Dimick

Figure 4: Graduate student, Laurel, tests attendees on their ability to smell and aroma and guess what it is. Laurel works within Dr. Ryan Elias’s lab. Photo by: Tom Dimick


Figure 5: Denise Gardner pours some of the commercial wines for attendees and explains how to pair them with locally produced cheeses. Photo by: Tom Dimick

Figure 5: Denise Gardner pours some of the commercial wines for attendees and explains how to pair them with locally produced cheeses. Photo by: Tom Dimick


Figure 6: Dr. Michela Centinari pours and explains the research wine trials. Attendees loved this portion of the program and were truly impressed with the quality wines produced by our research team! Photo by: Tom Dimick

Figure 6: Dr. Michela Centinari pours and explains the research wine trials. Attendees loved this portion of the program and were truly impressed with the quality wines produced by our research team! Photo by: Tom Dimick

The educational portion of this program was a big success.  Attendees learned about native and wine grape varieties grown in Pennsylvania, and how those grapes compare to table grapes that people see in grocery stores.  At the fermentation booth, participants learned how to measure Brix to determine potential alcohol and how a temperature-controlled stainless steel tank can be useful in wine production.  Additionally, our graduate students put guests’ nose-sniffing skills to the greatest test in seeing if they could guess various wine aromas without peaking at the answers!  It was enlightening to see our students teach the importance of these skills to develop a career in the wine industry.

The Penn State research wines that are made at University Park were also a big hit.  Explaining the purpose of research wines can be a slight challenge, as most of our wines are never finished.  This means that in order to emphasize a vineyard or winemaking treatment, fining, stabilizing, and finishing treatments (like oak aging) are kept to an absolute minimum or completely avoided.  In many cases, bottled wines will never see any oak or fining other than getting racked off of their lees.

Our primary display was on the Noiret wines, which was a project funded by the PA Wine Marketing and Research Board to determine if vineyard management treatments affected the concentration and perception of rotundone, the primary aroma compound associated with the Noiret variety that exudes a black pepper aroma.  The rosé wine, also made from Noiret, was an excellent contrast to the red wines produced from the same variety.  Pairing the wines with various cheeses produced by Berkey Creamery was an excellent way to also talk about wine styles produced in Pennsylvania and the importance of food and wine pairing with many of the local wines.

If you are interested in tasting many of our wine trials, please join us at the annual PA Wine Marketing and Research Board Symposium.  The 2017 Symposium will be held in University Park on March 29th(More details on this conference will be released soon!)

But what happened to that video?!  If you are still interested in evaluating our winemaking program, curious about what we have been up to for the past few years, please feel free to enjoy our short 12 minute video that highlights a small portion of our efforts to work with industry and participate in viticulture and enology research.  While the program is young, we have truly been fortunate to work with some pretty amazing people: commercial growers and producers that are interested in research, students developing expertise, and other academic colleagues that have been willing to collaborate with us as we build our programs.

We truly hope that you have seen or experienced some of the benefits of our programs, but if you would like to know more about what we do, please do not hesitate to contact us!  Our email addresses are readily available and we also try to document our regular activities on Facebook.  We honestly couldn’t do it without the support of people like YOU!

Enjoy the video!  We think it is fairly entertaining, a lot of work went into it, and it showcases a small fraction of the things we are trying to do at Penn State to help progress and educate the local wine industry:

Winemaking At Penn State Video

(If you do not have a dropbox account, simply hit “No Thanks” when the pop up window is displayed.  You can also do this if you would like to avoid logging into dropbox.)

Figure 7: Bottled research wines ready for tasting. Photo by: Denise Gardner

Figure 7: Bottled research wines ready for tasting. Photo by: Denise Gardner


2017 Retail Trends For Winery Tasting Rooms To Consider

By Dr. Kathy Kelley

With the New Year just over a week away, the number of reports, articles, etc. that predict what will happen in retail and food trends are filling my inbox and dominating the Internet.  Though overwhelming, I do enjoy sifting through these data and identifying trends that appear in more than one source and that could be useful to tasting rooms in our region.

The one trend that appeared quite frequently was the importance of creating a customer experience.  We have published a couple of blogs about creating an experience, which you can find by clicking on the following: http://bit.ly/2h1dM21 and http://bit.ly/2h1dzLZ.   Since you can refer to these past blogs about how to create an experience for your tasting room visitor, I selected three other trends for today’s post: being transparent, important flavors, and communicating with customers via text.


For a few years, consumers have expected businesses to be “transparent” with how they manage funds collected via their cause marketing programs.  Donors want to know how each dollar collected is distributed (http://bit.ly/2i6EdIB).  Some companies want to be transparent in every business aspect and they even make key employee salaries public (http://bit.ly/2i6K7ZY).  Without going to that extreme – what can a business do to meet the desires of their customers who have an interest in learning “where their money’s going rather than simply what it’s buying?”

An example presented in Vend’s 2017 Retail Trends and Predictions report (http://bit.ly/2gUbT74) is Everlane, a clothing business that promotes “radical transparency” (http://bit.ly/2h11bvA).  One of their principles is to be transparent in their costs.

By clicking on a wool-cashmere scarf that they sell, I learned that the true cost ($31.00) was derived from the following: materials ($16.40), hardware ($1.60), labor ($9.65), duties ($2.21), and transport ($1.30) (http://bit.ly/2i22LSR).  The retail price was $65; however, they are primarily an e-retailer, with some product available in boutiques in major metropolitan areas, so they have been able to “eliminate brick-and-mortar expenses and pass these savings on to” their customers.  Consumers and some magazines (e.g., Lucky Magazine, GQ, and Glamour), newspapers (e.g., Los Angeles times, The New York Times), and fashion websites (e.g., Style.com) appreciate this strategy and insight (http://bit.ly/2h3EwPv).

You may not feel comfortable providing a breakdown of why your bottle of Chardonnay costs what it does, but I’m sure that you get asked often why your wine is more expensive than a Chardonnay produced by a “massive conglomerate brand.” Reininger Winery, located in the Walla Walled Valley in Washington State, answered this question in a July 2012 blog post (http://bit.ly/2gV1urD).

Courtney Morgan, Reininger Winery Marketing Assistant, provided information to educate consumers about how factors (e.g. marketing costs, land prices, volume purchases) impact the final price of a wine.  Like Courtney, you probably would make note that “there is no question that a large conglomerate winery can make a good $8 wine,” but that there is something unique and special about the wine you produce and the wine in the bottle reflects the care and attention you take during harvest and the wine making process.

Do consumers get a sense of who you are as a brand?

Most likely your website has an “About Us” page that describes a little bit about your winery/vineyard and the owners.  Perhaps you even have some information about your wine maker or other key employees.  If the descriptions are brief, or merely mention an employee, their name, and their job title, consider adding information that them and who they are as a person.

screenshot-2016-12-21-19-43-02Brancott Estate in New Zealand, which I was fortunate enough to visit a couple of times during my 2011 sabbatical, has taken such an approach.  While a few of the key personnel listed hobbies and what they do on their time off, others described what specific tasks they oversee.

When I clicked on their “About Us” page, I learned that Patrick Materman, Chief winemaker, “decided he would study horticulture at Massey University” at age six, that he was awarded the title of “New Zealand Winemaker of the Year” in 2001, and his job entails “monitoring vineyard blocks, tasting fruit and determining the optimum harvest date.”  Eric Hughes, Winery Manager, is responsible for “turning harvested grapes into wines of the highest quality” and he is the head instructor at the Blenheim Dojo for Seido Karate.

If someone writes your blogs or posts your social media updates and readers merely see their first name in the byline – this could be a missed opportunity.  Wouldn’t you, as a consumer of products and services, what to “know” who is provided the information that you use to make a purchase?

John Morgan, who wrote “Branding Against the Machine: How to Build Your Brand, Cut Through the Marketing Noise, and Stand Out from the Competition” (John Wiley & Sons, Inc. 2012) stated that “What you do may not be unique, but you are.  This is why putting your personality into your brand is so important…Personal brands can coexist with a company brand.”  The author provided examples of businesses, one of which was Ford Motor Company, that does this well.  Scott Monty, head of the company’s social media, does “a good job of letting us know the people behind the logo.  Scott is building relationships with people and is a brand within a brand.”  Lastly, “People do business with people…Today people connect with your personality, content, and values.  Not your product or service.”


Throughout the year several magazines, food businesses, chef organizations, etc. develop lists of food trends.  The number of these resources can be overwhelming and some focus on the impact of a specific ingredient (e.g. turmeric, http://bit.ly/2i6KMe8).  I try to find trends that relate to particular types of cuisines and that are mentioned in several reports.  So, what cuisines might we be savoring in 2017?  Mintel, a provider of market research (http://bit.ly/2i6kdWA), predicts the following:

Cuban influenced cuisine

This food flavor trend is expected to gain greater appeal due to the U.S. travel ban to the island being lifted.   Consumers who travel to Cuba for leisure and business and eat Cuban food during their visit may then want to consume these foods when they return home.  Look for foods with rich sofrito sauce (Cuban sofrito is made with tomatoes, red bell peppers, and diced ham and differs from Dominican, Puerto Rican, and other sofritos, http://abt.cm/2i6g7Od) and pork-based dishes.

Korean, Filipino, and African flavors will become more prominent

Korean flavors such as kimchi (fermented cabbage dish made with garlic, salt, vinegar, spices, and chile peppers, http://bit.ly/2i6cJ5V) and gochujang (sauce made from chile peppers, salt, sticky rice, and fermented soybeans, http://bit.ly/2i6o71B) “are becoming mainstream as they are incorporated into everything from Polish sausages to ketchup,” and more Millennials (23%) “want to see more pickled ingredients on the menu, compared to 14% of all US consumers” (http://bit.ly/2i6kdWA).


Are you familiar with harissa (a chile paste made with smoked peppers, garlic, tomatoes, and a variety of spices and used in North African and Middle Eastern cooking, http://bit.ly/2i6fB2z), teff (a fine grain used to make breads and baked goods and can be steamed, boiled, or baked, http://bit.ly/2i6exM6), or piri piri (peppers used to make a sauce, http://bit.ly/2i6rvtb)?  If not, you may very well see them served in both full-service restaurants and dished out of food trucks.

Fire-grilled or smoked foods

Cooking food in a stove or oven is being overshadowed by consumer interest in foods cooked over a wood-fired grill.  The smoke flavor and aroma “can be incorporated into spreads, desserts, beverages…meats, marinades and sauces” with restaurants using specific types of wood to impart a particular flavor (http://bit.ly/2i6kdWA).

Regardless of whether you have already seen these foods incorporated into menus at local restaurants or if tasting room visitors have asked about possible pairings, now is the time to start developing a list of your wines to serve with these flavors.


There are several ways that customers can contact you to ask a question about your wine, tasting room, etc., or that you could use to inform them about an event or just say “hi.” Your customers; however, may really appreciate the ability to text message you rather than send an email or call you on their phone to ask you a question.

In 2015, 92% of U.S. adults owned a cell phone of which 68% of them owned a smartphone (http://pewrsr.ch/2iaveGn).  Another survey, administered in late 2014, revealed that text messaging was the primary activity smartphone users conducted on their phone.  Of the survey participants, 100% of those who were age 18 to 29 used their phones to text message (http://pewrsr.ch/2iawoS8).  Nearly all survey participants age 30 to 49 (98%) used their smartphone to text with just slightly fewer participants age 50 and older (92%) responding that they used their smartphone for this purpose.


If text messaging is the primary activity smartphone users conduct on their phones, might they be interested in using text to communicate with business?  According to a report published by The Center for Generational Kinetics, “some 36% of Millennials say they would contact a company more frequently if they could text them” (http://nws.mx/2h1uNZD).

Why do consumers prefer to send a text to a customer service department rather than call the company?  The top five reasons why U.S. and German consumers preferred text, according to a May 2016 survey conducted by Ovum, were:

  • “less time consuming,” 44% of respondents selected this reason,
  • “more convenient,” 42%,
  • “less frustrating,” 30%,
  • “enabled [them] to ask the company to text/call back,” 26%, and
  • “enabled [them] to have a record of the conversation,” 19% (http://bit.ly/2h1vt1p).

To facility a smooth texting experience, several companies provide 2 Way SMS services that allow businesses to send and receive text messages in real time, send automated replies based on keywords, send appointment reminders, and other communications (http://bit.ly/2h1r3rr).

One such company, SMS Global, a messaging solutions provider (http://bit.ly/2h1m8GT), described some of the things a business can do using 2 Way SMS:

  • Send coupons, offers, and inform customers about sales. SMS Global indicated on their website that “in many cases [their] customers yield a more than 300% increase” in offers and coupon redemptions “compared to email or hard copy offers” (http://bit.ly/2h1r6TW).

An example of a winery that uses text messaging to connect with customers is Chankaska Creek Ranch & Winery, located in Kasota, MN.  The winery uses text messaging to alert customers about the promotions as well as when they release their wines (http://bit.ly/2iaxaOS).

  • Increase email open rates. SMS Global clients experienced a 30 to 40% increase when consumers received a text “prompting [them] to check their email.”
  • Get customer feedback. Every so often, send your customers a text with a question or two and instantaneously learn about their thoughts and interests.

Why might a business want to incorporate texting into their marketing and communication strategy?  Kenneth Burke recently published a list of reasons on the Text Requests website (http://bit.ly/2iakkjA).  Some include:

  • Responding to consumers via text is a quicker way to answer their questions, allowing you to solve a problem before your competitor can, which may result in more sales.
  • According to Burke, “for the average person, texting is one of the more personal things we do every day.” His rationale is that we receive a lot of emails, many of which “are simply marketing and sales messages,” and phone calls, I’m sure that when you see an unrecognized telephone number on your screen that you automatically think that it is a telemarketer.  But, when you receive texts – you know who sent it and these texts are most likely “from people you have close relationships with.”
  • “Texting makes your business fully mobile.” Texting completes the cell phone usage experience.  If a consumer uses their phone to access social media apps, read emails, play games, and a multitude of other activities – then why not reach them on the device that is most likely to be by their side?

Of course, as with any other marketing and communication practice you implement, you will want to make sure that you follow the rules, which include an opt-in consent, directions on how consumers can opt out of text messages, and that message rates may apply (http://bit.ly/2iaFYEC).

We will continue to share trends that could be useful to wineries and winery tasting rooms in the New Year.