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Really, Really High pH Remedies

November 2009
 
by Tim Patterson
 
 
    HIGHLIGHTS
     

     
  • High-pH wines are fraught with disadvantages, but sometimes that’s what winemakers are faced with. All the available methods for dealing with super-high pH have their pros and cons.
     
  • Ion exchange by means of charged resin column equipment has been around for decades, mainly used by large-scale producers, but can work in a small-production, premium wine context as well.
     
  • More recently, at least two service providers have offered pH reduction through various kinds of sophisticated electrochemical membrane technologies, accomplishing the desired shift with more control and more selectivity.
     
  • The other alternative is to live with the pH, deal with the downsides it brings, and recognize the wine may not live forever.

Right now, winemakers all over the country—many of them here in California—are holding freshly minted wines, almost all of them red, with terrifyingly high pH levels. Wines that are so far out of textbook range they seem ready to explode in the cellar. I don’t mean pHs around 3.75; I mean well over 4.0, something no one does on purpose.

The winemakers know better; it’s just that something went haywire in the rush of the crush. And now it’s November, and there sit several hundred (thousand?) gallons of otherwise fine wine with a rogue pH that can’t easily be fixed by adding tartaric acid, blending or round-the-clock vigils.

Who ya gonna call? Potassium Busters?

I got interested in this particular winemaking bind through a barrel in my own garage from the 2008 harvest—a 30-gallon blend of Iberian varieties including a lot of Tempranillo, famous worldwide for sucking up potassium and registering alarming pH levels. After going through malolactic, it clocked in at a pH of 4.23 and a TA of 5.1 grams per liter. Ratcheting the pH down with acid additions would produce a wine resembling lemon juice. Meantime, my prize barrel tasted flat and tired, had a pale color and zip aromatics—it was more like a Petri dish for microbial activity than a sound wine.

So I called Livermore winemaker Tom Coyne, who advised me to apply a little emergency ion exchange: the oldest and probably least glamorous of the available fixes. And sure enough, my barrel rejoined the world of normal wine. In the process, I looked into the various other methods for pH rescue. These are not options anyone looks forward to, but if you have a good wine on life support, drastic measures may be appropriate.

Prevention, prevention, prevention

Nearly everyone I talked to about this issue started by saying you should never get yourself into such a situation, there are ways to prevent it, and so on. In a couple cases, it took half the phone call to convince my consultants that the premise of the article was, “OK, but it did happen—now how do I fix it?”

It’s certainly true that the earlier a super-high pH problem is identified, avoided or fixed, the better—for the wine and the worried winemaker.  The solution may mean work in the vineyard, and it means having a full understanding of the juice/wine chemistry from the minute it arrives. The sooner the problem is addressed, the less intervention and expense is required.

Sometimes harried winemakers (count me in) spot high-pH grapes, throw in a hunch’s worth of acid, hope it works and move on to the next batch of fruit demanding attention. The value of acid additions depends on the buffering capacity of juice and wine, meaning that a given addition of tartaric acid does not have the same effect in lowering pH from wine to wine. A little more testing of things like the proportion of malic and tartaric in the juice, and this math can be clarified and the chances of normalizing the wine from the start improved.

But sometimes all that analysis doesn’t get done in time, and there you are. Coyne says that one school of thought about how to deal with extra-high pH is denial—hoping the problem will go away, or maybe won’t matter that much, or can be fixed later.  With gobs of SO2, a microbial uprising can perhaps be quelled—leaving only the major problems of taste, aroma, color retention and longevity.

The pH Problem Deniers do have one consumer trend on their side: The vast majority of wines in the United States are consumed very soon after they’re bottled—aged only as long as it takes to get the wine back from the supermarket for dinner. If the wine can be dressed up with enough alcohol, something to fortify color, maybe a pinch of residual sugar, a little aromatic concentrate to get the nose back in play, it can be pleasant enough and consumed quickly. But surely there’s a better way.

Ion exchange
Ion exchange has been around since the 1950s, is widely used for various purposes throughout the food and beverage industry, and remains a common remedy for the lower-end, mass-production sector of the California wine industry. Depending on how the technology is used, it can aid in lowering pH, lowering acidity and various other alterations of wine chemistry.

The traditional set-up utilizes a column filled with resin beads, which are charged for their appointed task with one or another solution, and then the wine gets passed through. There are lots of resin possibilities, lots of charge agents, and therefore lots of possible outcomes.

Coyne, a former chemical engineer, concocted his own resin mix, which is charged with a solution of sulfuric acid, then rinsed out. When wine passes through the column rig he built, potassium ions (and likely calcium and magnesium) from the wine are absorbed into the resin, and hydrogen ions from the charged resin go into solution in the wine. Result: big pH drop immediately. Total acidity also goes up—not because any acid was added, but because the removal of all that potassium alters the buffering conditions, making the acid in the wine more effective.

Because the method is somewhat inexact—there’s no way to control or predict the precise change in pH—the treatment is done on a fraction of the problem wine, which is then tested and blended back into the untreated wine. It may take a couple of small batches to get the right balance, and there may be some need for old-fashioned acid additions for fine-tuning. This is not something anybody would do on a routine basis, but it gets the job done.

Ion exchange has often been criticized as too much of a brute force tool for upscale, fine winemaking. One obvious problem is that it creates toxic wastewater from the charging/rinsing, which must be detoxified and disposed of properly, adding trouble and expense.

The quality complaint has been that the method is not very selective, that various other positively or negatively charged ions can be inserted or stripped in the process—much like fining agents can affect more wine components than the one they’re being paid to remove. Some texts warn that ion exchange will put high levels of sodium into the wine—but that depends entirely on the resin of choice. Still, there is clearly some chance of pulling out compounds we’d like to have in there—pigment and other phenolic material, aroma precursors, nitrogen nutrient, etc. 

Alas, there’s not a lot of science on the sensory consequences of ion exchange. One intriguing piece of research came out of a 2003 study at the University of Arkansas (T. Walker, et al, “Quality, Sensory and Cost Comparison for pH Reduction of Syrah Wine Using Ion Exchange Or Tartaric Acid,” J. Food Quality 27, 2004, 483-496).

The pH of the subject Syrah was lowered from 4.24 to 3.48 by two resin-column ion exchange methods, four electrochemical membrane methods (more on this later), and traditional tartaric acid additions. In all cases, potassium went down, acidity went up, total phenolics went down slightly, and color and color density went up—though color improved least with the tartaric addition method. A trained, descriptive panel identified changes in several attributes and, significantly, the differences between the control wine and all the treated wines were greater than the differences among the various treatments.

Gary Main, an associate in enology and viticulture at Arkansas and part of the team behind the Syrah study, also was among those who told me that super-high pH is a problem to avoid, not a problem to fix. But in a pinch, he thinks the membrane solutions are probably superior to resin-column ion exchange, and that all of them can have a place in premium winemaking.

Tom Coyne says, based on his own basic lab work and sensory evaluation, that he has seen very little impairment in quality—certainly not much loss compared to the manifold benefits of getting the pH back into range. For what it’s worth, the pH of my troubled barrel went from 4.2 to 3.45 in 15 minutes, the acidity from 5.1 up to 6.2; better yet, the wine suddenly had a nose and a lively fruit expression. Some anthocyanins may have been left in the column, but the plummeting pH guaranteed much better total color and intensity.

Coyne has tried offering his services to other local Livermore Valley winemakers without much success. Maybe they’re influenced by the low-glam reputation of a Central Valley technique, maybe they’re pH deniers, maybe they’re waiting for the next new technology.

Kinder, gentler ion exchangers
And indeed, new equipment and approaches have come onto the market in the past year or two, commercial versions of the equipment used in the Arkansas study. Eric Dahlberg, president of Winesecrets, which utilizes two of them, jokingly described them to me as “kinder, gentler ion exchange.” The nugget of truth in that description is that the basic chemical modification is the same—getting potassium (mainly) out, and often getting hydrogen in.

Winesecrets’ STARS electrodialysis (ED) equipment, including mobile versions, has begun to make a show in the marketplace as a means of tartrate stabilization (see the October issue of Wines & Vines). The same machinery, with some parameter adjustment, can be used to drop pH by .3 to .4 units, and a volume of wine can be treated more than once.

This year, STARS has been joined by a more advanced relative from the same European developers, utilizing a process called bipolar electrodialysis; the new rig can achieve a slightly higher pH drop, and be run multiple times. The bipolar ED equipment includes a membrane that encourages hydrolysis, separating hydrogen ions from water and handing them off to the wine. Both technologies make use of membrane filters and electromagnetic fields; STARS treatment will lower pH and slightly lower acidity, while the bipolar ED treatment will lower pH and slightly raise acidity.

What both methods offer, Dahlberg says, is more selectivity than ion exchange, little or no effect on compounds other than the targets, and more precision—making it possible to dial in the precise pH being achieved. The wastewater from the bipolar ED setup also is easier to handle and recycle. Dahlberg predicts that the bipolar machines will eventually be the replacement for ion exchangers in the “big box” wineries.

And just in time for the 2009 harvest, Mavrik North America, which also specializes in treating wines for various maladies from excess alcohol to smoke taint, is introducing its own technology for pH reduction. Again, membranes are involved. But instead of treating the whole volume of wine, the process Mavrik has developed first separates the wine into retentate and permeate fractions through reverse osmosis, treats the permeate, then puts it all back together.

The operation, which can also be used for tartrate stabilization, removes potassium and also calcium and magnesium, present in very small quantities but a very strong base.

Again, the Mavrik option offers more potential selectivity and precision. President Bob Kreisher would be happy to get any wine down to the TTB lower limit of pH 2.8, but cautions that all of this technology depends on the availability of base material to remove—once that’s exhausted, chemical pH reduction hits a wall, and winemakers have to move onto other techniques.

Living—carefully—with high pH
Bruce Zoecklein at Virginia Tech was among those who mainly wanted to talk about preventing this situation. As a self-described advocate of “minimalist” winemaking methods, he’s never been keen on ion exchange and the kind of f rontal intervention required for big-time pH reduction—though he certainly understands how it works and why folks do it.

He suggests another possible approach—living with high pH, while being vigilant about its downsides. “The real issue,” he says, “is whether the wine is balanced, whether the perception of sweetness, acidity and phenolics come together. Sure, the wine’s longevity may be in doubt, but balance is what matters.”

Zoecklein isn’t advocating denial and neglect—his advice suggests paying a lot of attention and trying a lot of less-invasive measures. Even if tartaric additions can’t solve the whole pH problem, they can help, and can bring a necessary liveliness back to a flat wine. If you can’t blend away the pH, you may be able to blend in a little color fortification. Monitoring SO2 levels is, of course, a must. The list goes on.

The fix-it-up approach will never reclaim the perfect wine envisioned when those grapes headed for the crusher. For that matter, neither will ion exchange or the newer membrane-based methods. As every winemaker knows, the earlier a problem is solved, the fewer its consequences for the wine. But all these approaches can work—and all of them are enough of a pain to motivate winegrowers to avoid the problem next year.

No Tempranillo for this home winemaker.

Tim Patterson writes about wine and makes his own in Berkeley, Calif. Years of experience as a journalist, combined with a contrarian streak, make him interested in getting to the bottom of wine stories, casting a critical eye on conventional wisdom in the process. Contact him through edit@winesandvines.com.

 
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