Ohio Grape-Wine Electronic Newsletter

Editor: Imed Dami, PhD
Assistant Professor and Extension Viticulture Specialist
Department of Horticulture and Crop Science
Ohio Agricultural Research and Development Center
1680 Madison Avenue
Wooster, OH 44691-4096
Phone: (330)-263-3882
Fax: (330)-263-3887
E-mail: dami.1@osu.edu
 www.oardc.ohio-state.edu/grapeweb/


 
 
 
5 October 2007
 
 
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 Content:

2008 OGWC
ATA -- Potential Problem in 2007?
New Book on Grape Winter Hardiness
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2008 Ohio Grape & Wine Conference – Mark your Calendar!
 
The Ohio Grape & Wine Conference will be held on 11-12 February at the Shisler Conference Center at OARDC in Wooster, OH. Please mark your calendar. More information will be forthcoming.
 
ATA -- Potential Problem in 2007?
By: Timothy E. Martinson, Senior Extension Associate, and others
New York State Agric. Exper. Sta.

In much of NY and the Eastern US, its been a very dry year.  In Geneva, July and August showed 1.2 and 1.4 in measurable precipitation, well below the average 3 in. monthly - and about half of what the southern part of the Finger Lakes got during those months. 
 
This has made for clean, disease-free fruit, but also raises the possibility of developing Atypical Aging (ATA) in wines this year.  Many vineyards have had visible signs of drought stress this summer - resulting from that mid-July through end of August and into September drought period.  I’ve seen vineyards with modest growth, yellowing basal leaves, and drought-related leaf burns.  Along with an average to good-sized crop, this signifies a sizable dose of crop and drought-related vine stress in the 5-7 weeks around veraison in unirrigated vineyards, conditions which often lead to ATA off-flavors in white wines.
 
ATA flavors.  Wines with ATA potential may taste fine after fermentation and before bottling, but after a varying amount of time (6 mo to 2 yr) in the bottle may develop flavors described as: damp dishrag, furniture varnish, and ‘linden blossom’(or acacia).  Moreover, the wines lose varietal characters and aromas.  My own personal touchpoint for wines showing ATA is that they taste ‘flat’, and often there are waxy flavors and aromas.   Intensity of this defect ranges from barely noticeable to severe.  Please note that this isn’t a peculiar malady limited to New York or the Finger Lakes.  It was first described in Germany and Austria, and has been noted in wines from Washington, OR, and California as well as the northeast. 
 
Causes.  Exact causes and chemistry behind ATA are not well understood.  But the symptoms are particularly correlated to droughty years, and drought-related stress.  They are also more prevalent in fruit that is harvested before full ripeness.  In some years (like last year), sugars and acids may not be changing much, but flavors will continue to develop in late-maturing grapes such as Riesling.  You are much less likely to get strong ATA flavors if the berry and flavor development is complete. 
 
In an experiment we conducted in 2001-2003,  irrigation reduced and delayed appearance of ATA-like flavors in wines in our two drought years (2001 and 2002).  In those years, we also measured leaf photosynthesis and water potential weekly from several weeks before and several weeks after veraison.  What we found was a 5-7 week period around and after veraison when leaves were so waterstressed that photosynthesis was essentially shut down in the middle of the day.  This translated to a 4 degree brix difference in sugars at harvest, compared to irrigated vines without water stress. 
 
The question I would ask as a grower (or winery) is this:  Can I really afford to have vines with leaves not functioning for 5-7 weeks around veraison?  This season has provided moderate water stress after bloom, resulting in smaller berry size and less shoot growth.  This is good for reds.  But the severe water stress later in the season does not contribute to increased wine quality.  Irrigation (and other ways of managing water relations), in my opinion, will be increasingly important in the future.
 
Managing ATA:  Three ways to avoid or at least delay appearance of ATA in your wines are 1) harvest your crop when it is ripe, not before it is,  2) use irrigation in dry years to avoid vine water stress (already discussed), and 3) test and treat wines with ascorbic acid.  
 
Adding Ascorbic acid to wines:  Thomas Henick-Kling provided guidance for winemakers in testing wines for ATA, and also adding ascorbic acid at 100 ppm to wines at bottling to prevent or delay appearance of the off flavors.  Here is the original communication Thomas sent out:
 
ATA Test
Testing a wine for its potential to develop atypical aging defect
Thomas Henick-Kling (reprinted from 2003 Enology notes)
 
 
Divide wine that has been properly stabilized with SO2 into two aliquots (100 mL or more).  To one part add 150 mg/L ascorbic acid. Add nothing to the other part.  Fill into glass bottles, avoid large headspace, and seal well.   Place into oven at 40°C for 12 hours, or better 2 days.  Let wines cool and compare the flavor.  If both wines (with and without ascorbic acid) taste the same then the wine likely will not develop ATA .  If the wine without the ascorbic acid added has changed its flavor then it is likely to develop ATA soon.
 
[information from:  Staatliche Fachschule fuer Gartenbau und Weinbau Veitshoechheim, Germany]
 
When adding ascorbic acid to new wines please ensure that the wine is clear and has been racked off the yeast lees.  The wine should be SO2  stable (i.e. able to hold free SO2  in successive tests).
 
What’s the downside of Ascorbic acid? I’ve asked several winemakers and a few enologists about the ‘downside’ of adding ascorbic acid to wines.  My thought was this:  Instead of testing for potential ATA and using that information to decide whether or not to add ascorbic acid to wines, why not add it to all the wines potentially at risk?

I was told that at concentrations of 100-150 ppm, ascorbic acid should not affect flavor or other characteristics of the wine.  My take is that if you have vineyards with moderate to severe drought stress, the prudent thing to do would be to treat those wines with ascorbic acid.

From Gavin Sacks (Assistant Professor of Enology, NYSAES): Ascorbic acid generates hydrogen peroxide (H2O2) upon reaction with oxygen.   There needs to be sufficient free S02 to sponge up the hydrogen peroxide, or else ascorbic acid will act promote oxidation of the wine. 

From Ramon Mira de Orduña (Associate Professor of Enology, NYSAES): Please remember two aspects that should be specifically taken into account before ascorbic acid is added to any wine as a preventive measure

1.       The free SO2 levels have always to  be sufficient (see above)

2.       SO2 determination by the Ripper method will provide false positive (i.e. too high) readings when ascrobic acid is present in the wine.  Alternate methods should be used.  These include the ‘modified Ripper’ with a formaldehyde ‘blank’, and the ‘Aspiration’ (Aeration-oxidation) method (see references below for more information)

3.        If you require precise SO2 determinations after ascorbic acid analysis, please contact Ben Gavitt at the NYS Wine analytical laboratory at bkg1@cornell.edu or 315-787-2263 for SO2 determination by Flow Injection Analysis, which does not suffer from interference by ascorbic acid.

For more detailed information on ascorbic acid:

 Gavin recommends an article entitled New Findings regarding Ascorbic Acid in Wine , posted at: http://www.wynboer.co.za/recentarticles/200607acid.php3

Ben Gavitt recommends Techniques for chemical analysis and quality monitoring during winemaking, published by Patrick Iland Wine Promotions (Campbelltown, Australia) as a reference for alternate SO2 tests described above.

New Book:  Winter Injury to Grapevines and Methods of Protection
By Imed Dami, HCS-OARDC

I am pleased to announce the release of a new book titled "Winter Injury to Grapevines and Methods of Protection". This book was the fruit of a two-year effort by viticulturists in the Eastern US, including Tom Zabadal (Michigan State University) who led the project, Tim Martinson and Martin Goffinet (Cornell University), Mark Chien (Penn State University), and Imed Dami (Ohio State University). In my biased opinion (since I am a co-author), it is the best publication on the subject of winter hardiness of grapevines  (well...there was none prior to this!) This book is more than 100 pages with more than 100 color photos, graphs, and tables. Besides our synthesis of over 100 years of research and knowledge about the problem of winter injury, we added sidebars from growers who shared their experience in dealing with cold injury and methods of protection.

I highly recommend this book to every grape grower in Ohio and anywhere in the country where winter injury of grapevines is experienced. It is a bargain at $15.00. This Extension Bulletin #E2930 from Michigan State University can be ordered online at:http://www.emdc.msue.msu.edu/viewitem.cfm?INVKEY=E2930. Here is the Table of content to show the breadth of topics covered in this book.

WINTER INJURY TO GRAPEVINES AND METHODS OF PROTECTION

I.     ECONOMICS OF WINTER INJURY
1.     Economics losses from winter injury
2.     Risk management
II.  COLD HARDINESS OF GRAPEVINES
     Defining cold hardiness
2.     Seasonal changes in vine physiology related to cold hardiness
3.     Seasonal changes in vine anatomy related to cold hardiness
4.     Genetics: the variation in cold hardiness among grape genotypes
III.    WEATHER CONDITIONS THAT CAUSE WINTER INJURY TO GRAPEVINES
1.     Duration of exposure to a low temperature
2.     Rapid temperature drops
3.     Temperatures preceding cold episodes
4.     Repeated cold episodes
5.     Desiccation
6.     Local and regional climate effects
IV.    WINTER INJURY OF GRAPEVINES
1.     The anatomy of winter freeze injury to cane and trunk tissues
2.     Vine growth responses after winter injury
3.     Assessing winter injury to dormant grapevines
4.     Crown gall and its relation to winter injury
5.     Loss of wine quality due to winter injury.
V     MANAGING GRAPEVINES TO PREVENT WINTER INJURY
1.     Vineyard site selection
2.     Vineyard site preparation
3.     Choice of planting material
4.     Choice of training systems
5.     Pruning strategies
6.     Crop control
7.     Vine density
8.     Chemical applications to influence cold hardiness
9.     Insect and disease control
10.    Avoiding low temperatures
        Wind Machines.
        Insulating with snow.
        Insulating with mulch.
        Insulating with soil
        Protecting graft unions
        Protecting fruiting potential
       
11.   Vine nutrition
12.   Leaf removal
13.   Rootstocks
14.   Time of harvest
15.   Irrigation
16.   Row middle management
VI.   MANAGING WINTER-INJURED GRAPE VINES
1.     The cellular process of repair of freeze-injured canes and trunks
2.     Replant decisions
3.     Pruning and tying strategies in relation to the severity of winter injury.
4.     Managing sucker growth
5.     Nitrogen fertilization of winter-injured vines
6.     Cropping vines
VII.   TECHNOLOGY OF THE FUTURE