(Wines&Vines) - Tartrate stabilization, often called cold stabilization, is a wine treatment for the cosmetic benefit of avoiding tartrate crystal formation. Intellectually you know you don’t really need to do it, but you do it anyway. So the priority is to get it done while minimizing both the risk of degrading wine quality and cost.

Until recently, winemakers had few choices. Typically they would set their glycol chiller to 20° F or so, then cool a tank to 26°-28° F for several days and let it slowly warm back up on its own. To speed up the process, winemakers might seed tanks with potassium bitartrate (KHT), and/or use heat exchangers to warm up chilled wine. While refrigeration achieves the desired goal of providing tartrate stability by removing excess KHT, it:

a) takes considerable time to get the desired result, with a range of one to five weeks;

b) exposes wine to potential oxidation, as oxygen solubility in wine increases as temperature is lowered, and

c) increases product costs through energy required to chill and warm up the wine, product loss through tartrate lees, and labor spent cleaning a tartrate-encrusted tank. Finally, excessive energy use to achieve a cosmetic benefit doesn’t align itself with promises of sustainability. 

The good news is there are now alternatives to refrigeration being used by hundreds of commercial wineries, and others have settled the frontier ahead of you. Regarding adoption of new technology and methods, I have often said that winemakers want to “be the first to be second” in an industry where some brag about using more 18th century methods than the guy down the street.

There are two types of technologies now commercially available to achieve tartrate stability. Both methods provide instantaneous results, avoid the risk associated with oxygen exposure when chilling wine to 28° F and are cost effective. Be advised that the analyses to determine both wine suitability and tartrate stability success are different from what is used when chilling. Unlike refrigeration, wine condition is critical (these are added to clean, protein-stable wines very close to bottling).

The methods 

Electrodialysis: Commonly known by the brand name STARS (Specific Tartrate Removal System) and offered by Oenodia, electrodialysis is a process in which wine is pumped through a piece of equipment that captures and removes only tartrate ions. Once the wine has moved from tank A to tank B, the wine is stable. 

Tartrate crystal inhibitors: These include mannoproteins extracted from Saccharomyces cerevisiae yeast (brand names Mannostab and Claristar) and carboxymethyl-modified vegetal-origin cellulose polymers commonly known as CMC (brand name Celstab). They surround the KHT molecules and prevent them from binding to each other. Laffort USA offers Mannostab and Celstab, while Scott Labs offers Claristar.

Winesandvines.com and practicalwinerylibrary.com have archived several excellent reports over the years detailing how these methods work, how to use them properly, benefits and potential positive effects on wine quality. For this column, we spoke to several winemakers currently using these products in order to share their real-world experiences.

Electrodialysis (STARS)

Pauline Lhote has 13 years of winemaking experience and serves as the winemaker for Domaine Chandon in California’s Napa Valley. Chandon makes a wide range of sparkling wines and a substantial amount of still wine.

With annual case production of 450,000, Chandon has possibly the most experience of any wine operation using STARS, having started in 2007. Lhote noted that its use has grown to the point that it is the only way Domaine Chandon tartrate stabilizes its wines. She points out that first effect is on quality, as STARS produces wines with better mouthfeel and balance. Keeping wine at cellar temperature avoids potential oxygen pickup associated with chilling.

Lhote said that Oenodia provided excellent training, though it is an easy machine to learn and use. Chandon runs clean, post-cross-flow filtered wine and attains both potassium and calcium stability in one pass. She said the technology has evolved since Chandon acquired its unit in 2007 and is now much more automated.

Operationally, Lhote likes the immediate stability, saving weeks over chilling methods, and the elimination of lees losses. STARS gives greater certainty to bottling schedules; if you know the exact date that the wine will be cold stable, you can plan your bottling schedule with a high level of certainty.

Environmentally, STARS is much more energy efficient and green than mass chilling. The only downside is the water consumption associated with it, which will soon be improved by the acquisition of reverse osmosis equipment to recover a substantial amount of the water. At Chandon, 20% of the water is recovered, and the balance is treated and used for vineyard irrigation and landscaping.

Lhote says electrodialysis is “a great tool for pH adjustment” in place of tartaric acid additions. She explains that California grapes used in sparkling wine have higher pH than French grapes. Electrodialysis allows Chandon to adjust pH without increasing TA, making grape must more similar to what is found in France. Now the winemaking team adds much less tartaric acid at harvest.

Heidi Barrett, owner of the La Sirena and Barrett & Barrett brands in Napa Valley and an independent winemaker for several other world-class boutique wineries, also has used STARS for pH adjustment. Recently she had two lots of Syrah with pH greater than 4.0, plus high TA. The wines would be way too tart if more tartaric acid was added to lower pH. STARS was able to remove the potassium ions without touching the acidity. Barrett was skeptical at first but now thinks STARS is “pretty cool. It doesn’t harm the wine; there are no off, cooked or synthetic flavors or aromas. It simply lowers pH.” Oenodia processed the wine in half a day, and Barrett said she would definitely use it again, adding, “The wines are happily aging in cave right now.”

Petar Kirilov is the winemaker for Meadowcroft Wines in Sebastopol, Calif., producing between 20,000 and 25,000 cases per year. He uses electrodialysis to decrease processing time, improve wine quality, and for sustainability.

Kirilov pulls wine out of the barrel, gets it heat stable and then brings in Oenodia to provide cold stability, noting, “Everything can happen in one week.” The method improves wine quali ty by “bringing the fruit up” and providing a fresher flavor, plus pH can be adjusted at the same time, if needed.

He sees STARS as relatively green. It saves a lot of energy. It does use some water, but when compared to the amount of water and chemicals needed to clean tartrate-encrusted tanks, it may not be worse.

Maintaining wine purity is important to Kirilov, who notes that STARS avoids an “addition” to wine. (He tries to avoid fining agents for the same reason.)

When evaluating a piece of new equipment like STARS, I recommend avoiding the trap of looking at it as a capital equipment purchase. Like most expensive systems, it can be brought in as needed, along with an experienced technician. You pay only a per-liter fee. Compare your “rental” cost to the total cost of chilling (electricity, wine losses, labor to clean tanks, etc.)