Review of the Eastern Winery Exposition
(EWE) Conference 2013
The material presented at the 2013 Eastern Winery Exposition (EWE) in Lancaster, PA covers every
aspect of winemaking: from being a newcomer to the industry and teaching the basics, and
groundbreaking viticulture/enology research reviews, to winemaker roundtables that emphasize stylistic
goals of specific varieties. This year Seyval, Viognier, and Traminette were covered as the varieties of
choice. It was incredible to evaluate some of the stylistic production techniques taking place in the MidAtlantic to refine these varieties. If you have not yet attended educational sessions at EWE, I highly
recommend them. You never know what production ideas could generate from these teachings and
tastings!
For
more
information
on
the
EWE
Conference,
please
visit:
http://www.easternwineryexposition.com/
This following report will review a few of the talks that I attended at the 2013 EWE Conference:
Phenolic Management for Aromatic White Wines
Winery Energy Savings: New (and Revisited) Technologies
Strategies for Sour Rot Reduction/Avoidance
Phenolic Management for Aromatic White Wines
Speakers: Chris Gerling and Diane Schmitt (Cornell University)
What is a phenol? Chemically speaking, phenols are a group of compounds that
contain one or more hydroxyl groups (-OH) attached to a benzene ring (refer to side
image). Although a simplistic structure, this compound itself is not found in wine. It
provides the basic backbone to the two different groups of phenolic compounds in
wine:
Flavonoids which contain 3 phenol structures bound together, and include anthocyanins,
tannins, catechins (flavan-3-ols) and flavonols.
Non-Flavonoids which do not contain a 3-ringed structure, and include hydroxycinnamates and
stilbenes (most notably resveratrol).
The bulk of phenolic compounds in white wines are hydroxycinnamates, other non-flavonoid
compounds, and catechins (flavan-3-ols) (Kennedy et al. 2006), which are derived from pulp, skin, and
seeds of white grape varieties. In comparison to red wine varieties, white wines contain a minimal
concentration of phenolic compounds (Kennedy et al. 2006). It is believed that these groups of phenols
are of interest as they may contribute to a white wine’s color, browning potential, and bitterness.
Most research manipulating the phenol content in wines has been focused on red varieties. In terms of
processing, it is well documented that to extract more phenolics in red wines, winemakers need to give
grape must longer extraction times with skins, higher [fermentation] temperatures, and retain higher
ethanol concentrations by the end of fermentation. But are these processing techniques applicable and
practical for white wines?
Lee and Jaworski (1988) have noted a higher concentration of flavan-3-ols in white wines with increased
skin contact time. However, this practice is known to enhance white wine color, and it should be noted
that flavan-3-ols are more easily oxidized (i.e. lead to browning) compared to other phenolic structures.
Additionally, Noble (1998) found that hydroxycinnamates may contribute bitterness to a wine. It has
been assumed that manipulation of hydroxycinnamates will directly alter the bitterness of a wine.
However, recent research has found that this group of compounds actually non-directly influences
bitterness as many of them are found in sub-threshold concentrations. Therefore, it is believed that
bitterness from hydroxycinnamates in wines may be caused by synergistic interactions of several
compounds.
Diane Schmitt’s research focused on skin contact time techniques on several white wine varieties:
Riesling, Gewürztraminer, Traminette, Valvin Muscat, La Crescent, Frontenac Gris, and NY 76.0844.24.
Cold soak and skin contact time during fermentation treatments were manipulated, and evaluated for
phenolic content of juice and wine. Generally, an increase in phenolic compound extraction was found
with increases in cold soak time duration. The investigators noted that there were some aromatic
changes associated with these wines subjected to longer skin contact times. This research is on-going
and will probably be reported on more in the near future through Cornell University Viticulture and
Enology programs.
What does this mean for white wine makers? Phenolic extraction may be a stylistic preference for many
winemakers producing white wine. Several varieties evaluated were left on the skins for enhanced
aroma/flavor extraction and/or tannin extraction. It’s essential to remember that while skin contact
time for white varieties may be practiced for aroma/flavor extraction, it will also have an effect on other
chemical properties of the wine such as tannin extraction. The same is true for the opposite approach: if
the wine is given longer skin contact times for enhanced tanning extraction, it will most likely have an
effect on the wine’s aroma/flavor. Such processing decisions need to be considered holistically. As with
many other processing options, there is never one easy solution that has an effect independent of other
wine factors.
References:
Kennedy, J.A., C. Saucier, and Y. Glories. 2006. Grape and wine phenolics: history and perspective. Am. J.
Enol. Vitic. 57(3): 239-248.
Lee, C.Y. and A.W. Jaworski. 1988. Phenolics and browning potential of white grapes grown in New York.
Am. J. Enol. Vitic. 39(4): 337-340.
Noble, A.C. 1998. Why do wines taste bitter and feel astringent? In Chemistry of Wine Flavor. A.L.
Waterhouse and S.E. Ebeler (Eds.), pp. 156-165. ACS Symp. Ser. 714. Am. Chemical Society,
Washington, DC.
Winery Energy Savings
Speaker: Dr. Bruce Zoecklein (Virginia Tech University)
A complete summary of Dr. Bruce Zoecklein’s talk regarding energy use in wineries can be found in his
Enology Notes #163: http://www.apps.fst.vt.edu/extension/enology/EN/163.html#1. The outline of his
talk includes the importance of winery sustainability, the use of energy in the winery, and winery design
alternatives to optimize efficiency. I highly encourage a review of this outline, as it highlights important
problem areas in a winery as well as options for improvement.
It was noted that a lot of research or commercial development on winery sustainability is being done on
the west coast, but this has been more of a forced effort by state government regulations more so than
generalized progress in the industry. Many of these practices can be implemented by smaller wineries
in the Mid-Atlantic region.
The greatest energy use (40-60%) in the winery is caused by refrigeration. Refrigeration, of course, is
utilized throughout several places during wine production: cooling wine juice, tartrate stabilization, tank
storage, and wine transfers. The following discusses several potential methods to reduce energy use for
small to mid-sized wineries.
As refrigeration is such a large energy consuming process, several enhancements can be suggested for
better efficiency. With white wine varieties, settling of juice is almost always done using refrigeration.
One way to minimize refrigeration use for juice settling is by flotation. Flotation involves pumping large
gas bubbles through the wine juice. The bubbles adhere to particulates in the juice and float to the top
of the tank as a cap. The clarified juice remains below the cap and can be separated. This process can
reduce separation time by hours, and is a quick energy-saving tool that is utilized by several wineries in
the Mid-Atlantic region.
Tartrate stabilization can be a large energy and economical cost for wineries as well. For a generalized
review on cold stabilization (theory, manipulation, and maintenance) please refer to Virginia Smith’s
primer at: (http://extension.psu.edu/enology/analytical-services/assessment-of-cold-stabilization/view).
Dr. Zoecklein discussed several methods that can cut down on energy use related to the cold
stabilization process including electrodialysis (ED) and inhibitor agents. ED stabilizes tartaric acid by
passing wine through an enclosed electric bed, which separates out positively and negatively charged
ions. As tartaric acid is negatively charged in wine, it is bound to one of the membranes on the electric
bed, hence separating out the tartaric acid from the wine solution. Positively charged ions (such as
potassium or calcium) pass through the membrane and are retained in the wine. Although the cost
associated with purchasing an ED is high for an individual winery, there are companies that offer ED as a
wine service. Vitis Labs (http://www.vitisresearch.com/aboutcarey.htm) currently offers this service for
Mid-Atlantic wineries.
Other energy reduction processes include the use of inhibitor agents, most notably
carboxymethylcellulose or CMC, to reduce the use of electricity for cold stabilization. CMC acts as an
inhibitor agent by coating the tartaric crystal nucleation site. Use of CMC does not change the pH or
titratable acidity (TA) of the wine, and has not been noted to cause any sensory changes to wines.
Additionally, use of CMC has become easier in the recent year, as most suppliers now have TTB approval
for use and sale. However, as with other additives to wine, several potential disadvantages for CMC use
include the following:
CMC is a synthesized cellulose-based product (not natural)
Wines must be “bottle-ready” (protein stable) prior to its application
CMC is not often recommended for high tannin varieties and some rosés
CMC has the ability to interact with proteins and cannot be used with wines that have been
treated with Lysozyme
There is the potential for CMC to interfere with filtration
Questions on the longevity of CMC-treated wines remain unanswered
In terms of enhancing efficiency for tank storage and wine transfers, the most common
recommendation is to improve insulation of these equipment pieces. Additionally, if glycol is being used
in the winery, insulating the glycol heater can enhance energy efficiency. For more practical energy
saving
solutions,
please
refer
to
Bruce
Zoecklein’s
Enology
Notes
#163
(http://www.apps.fst.vt.edu/extension/enology/EN/163.html#1).
When it comes to sustainability, small changes can go a long way. All of the solutions discussed here are
currently being utilized at several wineries in Pennsylvania and the Mid-Atlantic region, in addition to
wineries around the world. For more information on west coast sustainable practices, the Wine
Institute (http://www.wineinstitute.org/) provides several reports that could be pertinent to MidAtlantic wineries.
Strategies for Sour Rot Reduction/Avoidance
Speaker: Cristina Huber (Brock University)
Cristinia Huber gave an intriguing talk that reviewed the problem of sour rot in many vineyards across
the Mid-Atlantic and through Canada. One of the most interesting points that she made during her talk
was the fact that in Niagara, winemakers will actually reject incoming grapes with an acetic acid content
(in the must) that is 0.20-0.24 g/L acetic acid or higher. This rejection is based on the principle that such
a level, the grapes contain spoilage organisms in a high enough concentration to contaminate winery
equipment or exacerbate the problem of volatile acidity (VA) for that given wine variety. The use of
such a strong quality control measure is an indication of the quality level of wines produced from the
Niagara region. This quality step is one that could be utilized for wineries in the Mid-Atlantic developing
protocols for receiving/rejecting grape deliveries at harvest.
Many microorganisms have been identified from sour rot infected grapes: Acetobacter (acetic acid
bacteria), Aureobasidium, Bacillus, Pichia, Candida, and Hanseniaspora. These bacteria and yeasts often
exist as a dynamic population, and growers or winemakers have no way to predict how these
microorganisms will act throughout the extent of processing.
Ms. Huber’s research focused on identifying those microorganisms that actually contribute to creating
rot compared to those that actually produce acetic acid, the volatile component of sour rot that can
easily be sensed during a walk through a contaminated vineyard. Her findings indicated that
Acetobacter (acetic acid bacteria) and Hanseniaspora uvarum (yeast) were the most potent of the
microorganisms to cause sour rot, but that they needed a penetration point in order to infect the
berries. This means that simply coating the berries with infectious microorganisms is not enough to
cause a sour rot infection; an injury point is required. Those microorganisms identified that actually
produce acetic acid (in descending order) included Gluconobacter (acetic acid bacteria), Acetobacter
(acetic acid bacteria), Hanseniaspora (yeast), and Candida (yeast).
The remainder of her talk focused on inhibiting sour rot infections in the vineyard. However, for the
purpose of the paper, I will discuss the importance of winery sanitation practices in relation to
processing sour rotted fruit.
From an enological perspective, the identification of infectious organisms from this work is incredibly
valuable. It gives winemakers an idea of what microorganisms are coming into the winery with a sour
rot infection and how to potentially control processing to minimize contamination, growth, and
proliferation of sour rot in the winery. Acetobacter and Gluconobacter species are significant
contributors to volatile acidity (acetic acid concentration). These are aerobic organisms, requiring
oxygen for growth. Winemaking decisions throughout processing of infected sour rot fruit should
highlight minimal oxygen input. To do this winemakers are advised to:
Avoid cold soaks (too much contact time with spoilage microorganisms)
Minimize pump-overs or punchdowns to avoid constant oxygen exposure
Consider co-inoculation (yeast + MLB during primary fermentation) to minimize the time period
that the wine is left without sulfur dioxide treatment and oxygen exposure
Keep finished wines topped in tanks or with gas in the headspace
Consider sparging with a constant and fine stream of carbon dioxide for those tanks that have
headspace
Minimize moving the wine, especially with use of pumps
Manage and maintain sulfur dioxide treatments to the appropriate inhibitive level at the wine’s
pH
Avoid cross contamination or blending of infected wines into clean wines
Utilize sterile filtration at bottling
Regulation of acetic acid bacteria proliferation can also be controlled through temperature
maintenance; keeping the wines below 50°F has been shown to inhibit their growth. However, utilizing
proper sulfur dioxide management will maintain wine stability and inhibit further growth of both acetic
acid bacteria and spoilage yeasts.
Hanseniaspora and Candida are both spoilage yeasts that contribute to the sour rot flavors. Inhibition
and control of these yeasts can by controlled by:
Commercial yeast inoculation during primary fermentation (which will outcompete the native
spoilage yeasts that come in on the fruit)
Minimize oxygen exposure throughout processing
Retain sulfur dioxide management strategies to inhibit proliferation of spoilage yeasts
Proper cleaning and sanitation practices should also ensue in a winery processing sour rotted fruit.
These microorganisms are capable of producing biofilms that can linger in the winery for weeks,
months, or years and become more resistant to sanitation practices as time progresses. Additionally,
biofilms are great sources for feeding insects that spread contamination to other areas of the winery
and into other wines.
Proper sanitation regimes should include a cleaning step, rinsing step, and sanitation step. Bins and
equipment that comes in contact with sour rotted fruit should be properly cleaned (scrubbed) and
sanitized to avoid cross contamination of the sour rot infection onto clean fruit or wine. For more
information on sanitation options for wineries, please refer to the 2013 Wineries Unlimited Review on
the Penn State Extension Enology website (http://extension.psu.edu/enology).
Denise Gardner, Penn State Extension Enologist
March 2013