New path to tartrate control: electro-dialysis received well, but many reluctant to jump on board first.
Conventional cold stabilization in large refrigerated tanks takes a great deal of time--from a minimum of two to sometimes several weeks--running up the electric meter 24/7. It is not the most precise treatment in the toolbox, requiring testing for completion and sometimes running over the expected duration. It's a lot of time and trouble for what is essentially a cosmetic measure designed to keep consumers from freaking out at the sight of harmless, tasteless, yet unsightly tartrate crystals in their bottles or glasses.
But achieving cold stabilization in white wines and many mass-market reds remains a cost of doing business. Electro-dialysis--using a combination of membranes and a mild electrical field to promote ion movement--has shown the potential to lower energy costs, dramatically shorten processing time, fine tune the resulting wine chemistry, reduce wine loss and preserve, if not enhance, wine quality.
The only drawback: Capital investment costs arc not for the faint-hearted.
The electro-dialysis alternative
Winemakers have experimented with electro-dialysis for years, including some early versions tried by Gallo in the 1960s and 1970s. The French company Eurodia Industries introduced the first commercial installations of its equipment in Europe in 1998. In the United States, Eurodia's machines are distributed through Wine-Secrets, with locations in Northern and Southern California, Oregon, Washington and British Columbia. WineSecrets has dubbed the equipment STARS--for Selective Tartrate Removal System.
Using STARS, wine to be treated makes a single crossflow pass using a series of polymer membranes that separate potentially de-stabilizing ions--potassium, calcium, tartrate salts, etc.--with the help of a 5-amp electrical current. Unlike bulk chilling, which can noticeably reduce tartaric acid content, electro-dialysis barely lowers that needle, instead removing potassium ions and bitartrate base that can combine into potassium bitartrate and precipitate out of solution as crystals.
Users report only a very slight drop in tartaric acid, down around 0.1 gram per liter; pH also routinely drops slightly, in the .1 or .2 range. By changing processing parameters, the pH drop can be pushed further. Since the offending ions end up on the far side of the membrane barrier, in a kind of watery brine, there is no sludgy slurry at the bottom of the tank to discard or filter for wine retrieval, translating into less wine loss. At Domaine Chandon, sparkling winemaker Tom Tiburzi thinks the wine saved could pay for the unit they purchased in four years' time.
Two major evaluation studies of the electro-dialysis technology have been conducted, both funded by grants from the California Energy Commission, one involving PG&E and Fetzer Winery, another more recently involving Southern California Edison, Cal State Fresno and Cacciatore Fine Wines in Pixley, in the Central Valley's Tulare County. Findings on the energy use comparison are eye-popping: leaving aside some minor methodological issues about what detailed costs get counted for which method, the PG&E/Fetzer study, done side by side on 20,000 gallons of Pinot Grigio per treatment, found that bulk chilling consumed 22,965 kilowatt-hours (kwh) of electricity during 1,108 hours, while electro-dialysis drew only 170 kwh during a 31-hour period (equivalent to 6,076 kwh during a 1,108-hour period). Water use was higher--by 3,000 gallons--with electro-dialysis, but WineSecrets now has an additional module for recycling the ionized brine.
The greatly increased speed of processing is clearly important: It saves time, improves winery efficiency and removes the fear of blowing bottling schedules. According to Eric Dahlberg of WineSecrets, this combination of convenience and control is the main reason that smaller wineries--20,000-case operations that would never dream of buying a STARS rig--still contract for mobile services, even if the cost per gallon in small lots works out higher than it might for their own in-house bulk cold stabilization.
The reason small wineries aren't in the purchase market is simple. Dahlberg says an 800-gallon-per-hour system costs approximately $250,000, including stability analysis capacities; a 1,600-gallon-per-hour version comes in at $400,000. The water-recycling module adds about 15%. Replacement membranes aren't cheap, either. Dahlberg also estimates that bulk chilling for large lots costs around 7 cents per gallon (more like 12 cents for small lots); mobile-processed small lots (with fixed setup costs) can be somewhere between 25 and 50 cents, larger runs somewhat lower, and that once you've bitten off the capital costs of STARS equipment, the per-gallon costs drop to between 3 and 5 cents.
So far, WineSecrets has sold five sets of equipment: to St. Supery and Domaine Chandon in Napa, to the Terravant Wine Co. custom crush operation in Santa Barbara, Pacific Rim in Washington state, and Diamond Estates in Ontario, Canada. Dahlberg says resistance from other large wineries has partly stemmed from a degree of conservatism on technology matters. "It's hard to be the flag bearer for something that doesn't work out. This industry is littered with the bones of one technology or another from Europe that didn't work, and nobody wants horror stories." He see interest picking up, in part because the economic pressures of the recession mean capital expenditures are likely to be geared toward cost reduction efforts.
OK, but what about wine quality?
At St. Supery, assistant winemaker Tom Reese says they did extensive chemical and sensory testing from side-by-side trials, using a mobile unit from WineSecrets before investing in STARS in late 2007. Since there is no way to use electro-dialysis in bench trial, carboy-sized lots, this meant commercial-scale lots of Sauvignon Blanc.
Analytic differences were small, including a slight .1-.2 drop in pH. This turned out to be the wine chemistry marker for a slight but noticeable difference noted in blind sensory tests--a bit more perceived acidity, a brighter taste and righter mouthfeel, which the testers preferred, even though the titratable acidity itself hardly changed.
Some reduction in VA also was identified. The St. Supery team then did a second trial with its Virtu white Meritage blend, a richer, barrel-fermented wine with different organoleptic properties, and again liked the results. The STARS system also has been used in one case simply for pH reduction on a lot of high-pH red wine, successfully lowering the pH by .3. The 2008 vintage is the first to make full use of the equipment.
Tom Tiburzi at Chandon also reports that they did extensive trials before taking the plunge--not surprising since the product lines of sparkling houses depend so much on fine points of acidity, wine balance and sensory impact. Sparkling wine processing also presents additional issues relative to cold stabilization, both in the testing of alternate methods and in production runs.
Cold stabilization for sparkling wines is done once the base wines are completed and before secondary, in-bottle fermentation. With traditional bulk chilling, Tiburzi says, the reduction in tartaric can skew a wine's structure, so trials are conducted beforehand to see if additional tartaric needs to be added before cold stabilization to get the final proper result.
For the test, the same adjustment (if any) was made for wines going through electro-dialysis, plus a compensation for the expected. 1 drop in TA, to make sure the sensory tests weren't just picking up differences in acidity. Alcohol levels also must be anticipated; after a secondary fermentation, sparkling alcohol is likely to be 1.5% higher, again affecting both chemistry and sensory.
In the end, the side-by-side comparisons came out well. Analytically, Chandon found the expected very slight drop in pH and TA. Stability, measured by conductivity, was nearly identical. Sensorily, using duo-trio tests, no significant differences were observed in three sets of trials.
The technology has also been applied to red wines, both for Chandon's sparkling rose and sparkling red. In the case of reds, Tiburzi notes, wines that start cold stabilization (by either method) with a pH of 3.60 or above can actually develop higher pH through the treatment, which may require an acid correction--somewhat trickier for electro-dialysis, since there is no way to do a bench trial beforehand. Tasting and monitoring become very important.
Tiburzi points out that tartrate crystal control is especially important for sparkling wines, because it is hard-edged surfaces--bottle imperfections, intentional imperfections in crystal glassware, or potassium bitartrate crystals--that serve as the launching pads for those wonderful streams of bubbles. A bottle full of tartrate precipitate--produced, say, by stashing a bottle in the freezer for a quick pre-celebration chill--would likely produce a gusher on opening.
Reds in Fresno
Finally, the Cacciatore/Southern California Edison/Cal State Fresno study, besides verifying the potential for energy savings and efficient control, has involved extensive analytical and sensory evaluations. The results of this study, recently concluded, are not yet published or public, but researchers Robert Wample and Ken Fugelsang gave Wines & Vines a small preview.
The results for wine quality and chemical composition are generally quite positive. But the most intriguing aspect concerns quality issues with various methods for red wine production: The study revolved around large lots of Syrah and Cabernet Sauvignon. While cold stabilization often brings white wine to mind, a great deal of mass-market red wine goes through the process, too, in part because its storage conditions down the road may be less certain than those for premium wines, and in part because of potential consumer reaction.
And for reds, one apparent difference between methods is that traditional bulk chilling seems to take some amount of pigment and structure elements with it in those precipitated bitartrates--and electro-dialysis doesn't. It's even possible that electro-dialysis might raise total anthocyanin and total phenolics--suggesting that removing those troublesome ions may actually put some phenolic material back into solution. The Fresno results, when published, will likely add some interesting dimensions to this whole topic.
Energy Use Comparison BULK CHILLING 22,965 kwh ELECTRODIALYSIS 6,076 kwh PG&E/Fetzer study on 20,000 gallons of Pinot Grigio per treatment during a 1,108-hour or equivalent period.
* In recent years, electro-dialysis has begun to emerge as a mainstream alternative to traditional bulk chilling as a means of achieving tartrate control in wine production.
* Electro-dialysis, using European technology distributed in North America by WineSecrets, removes ionic salts through crossflow membranes in the presence of a mild electrical current, rather than forcing precipitation by chilling.
* Substantial cost savings from reduced energy consumption have been documented, but evidence is also accumulating that electro-dialysis can have positive effects on wine quality.
"Our results showed no significant sensory difference between methods. TA in the electrodialysis wine dropped O.lg/L, the pHs were not significant."
--Tom Tiburzi, Domaine Chandon
"Electro-dialysis is fabulous technology. The most expensive part of winery operations is energy to drive cooling jackets."
--Ken Fugelsang, researcher
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|Comment:||New path to tartrate control: electro-dialysis received well, but many reluctant to jump on board first.(WINEMAKING)|
|Publication:||Wines & Vines|
|Date:||Oct 1, 2009|
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