This article orginally appeared in the June 2001 issue of Wine Business Monthly
Originating in the Madiran region of southern France, where the Tannat grape produces exceedingly tannic wines, the French technique of micro-oxygenation has been in commercial use there since 1991. Several US wineries have developed interest in micro-oxygenation in the past few years, with 1999 being the first big year of implementation in California.
Dr. Vernon Singleton, now retired, first elucidated the chemical mechanisms and developed the "vicinal diphenyl cascade" mechanism theory by which wines consume oxygen and build structure. Building on his discoveries, Patrick Ducournau invented the technique of micro-oxygenation, and his development company OenoDev has since manufactured and implemented thousands of micro-oxygenation units throughout the world where the technique is applied under the firm's guidance. France is the clear leader in micro-oxygenation, with about two thousand units in production. Italy is second with about a thousand units, followed by South Africa and Chile. There are about 25 wineries practicing micro-oxygenation in the U.S. Australia has just begun to venture into micro-oxygenation.
Vinovation, Inc. represents OenoDev in the United States. Co-owner Clark Smith explains, "The technique may be a uniquely useful tool in what we call Integrated Tannin Management (ITM). We act as a focal point for wineries to organize a coordinated experimental plan. Smith reasons that, "The introduction of pure oxygen into wine is hazardous to its quality. We urge clients to diligently monitor their experimental wine and to limit lots within the bounds of acceptable risk. Our confidence in the system is, however, rapidly improving as we gain experience."
The aim in micro-oxygenation is to bleed oxygen in at just the right rate--which may vary from 0.25 to 100 milliliters per-liter per month--without overexposing the wine to it. Costs, according to Smith, run about two thousand dollars per wine tank. The purpose is to bring about desirable changes in wine texture and aroma that cannot be obtained by traditional aging techniques. The goals of micro-oxygenation include the restructuring of tannins and mouthfeel, color stability, aroma integration, decreased sulfide and reductive aromas, and increased longevity potential. What it does not do is promote early release or premature aging of wine.
A collaborative study is in the works, with University of California at Davis, California State University at Fresno, Virginia Polytechnic, and seven wineries participating with specific wines, including Havens Merlot, Hogue Merlot, Horton Touriga Nacional (a Port variety), Mondavi Cabernet Sauvignon, Sebastiani Merlot and BV Cabernet Sauvignon. Smith notes that Fresno will make two-packs of their wines available for sale and comparison: "before" and "after" Barberas.
There are issues still outstanding regarding micro- oxygenation, such as the long-term effects, Brettanomyces effects, sulfide dimers and pyrazine degradation. Smith stresses that winemakers must be willing to commit time and work to micro-oxygenation. "In some ways, I feel like a dynamite salesman. Everybody just wants a stick, but you need support and training too, because if you fry your wine and micro-oxygenation doesn't work, you're poisoning the process for everyone. You've got to buy the education with the stick of micro-oxygenation dynamite."
There are major misconceptions about the technique, according to Smith. The first is that some winemakers want to employ micro-oxygenation to save labor on racking barrels. "This use of O2 is not micro-oxygenation but rather what we call 'clique-que-age) is used to accelerate that period. Harmonization is the most difficult phase to follow because at this time wine is most sensitive and changes less reversible. Risks include the development of palate dryness, and excessive maturity accompanied by lost freshness and oxidized aromas.
Partial treatment with oxygen can be worse than none at all. If the wine is bottled too soon or if the tank is not aerated, and if the reduction power is high, reductive flavors can develop in the bottle. Micro-oxygenation is not primarily intended for use with problem wines. It supplements rather than replaces the action of the barrel. "The ideal situation," Smith says, "is to work with concentrated wines needing stabilization, not remedial salvaging, and refinement through prolonged aging for good balance of structure to roundness."
Practical Applications
Dr. Christian Butzke, associate specialist in cooperative extension at
UC-Davis, moderated a micro-oxygenation panel presentation at the Unified Symposium in January, at which he observed: "Impact of astringency is possibly the most important aspect of micro-oxygenation. The most important reaction of O2 with phenolic components in wine is the formation of quinones and more importantly the formation of peroxide, the oxidant that can work on the ethanol to produce acetaldehyde, one of the characters that we get in oxidized wines and that plays an important role in phenolic components.
"It becomes more obvious in our research in hard and soft tannins and phenolics research in general, that the larger-molecule tannins are not as important as the loss of the lower monomers and the smaller molecular-weight phenolic components. We're looking at a loss of small molecules rather than the development of big, soft tannins," says Butzke. "Most of the bigger components that are developing are not able to access the sensor on your tongue and make a difference when it comes to astringency for instance. The quinones can also pick up reduced components where the aroma aspects come in. It's a fine balance between oxidizing the reduced sulfur components and getting them out of the wines."
Laurent Lyothier, research assistant winemaker at Domaine Chandon in Yountville, California, has been studying micro-oxygenation in white wines since 1998. "The applications for micro-oxygenation in white wine that we have experimented with at Domaine Chandon include hyper-oxygenating must, addition of oxygen to yeast cultures, white wine aging with lees in tanks, and oxygen for green tannins or flavors. The control of oxygen is important in malolactic fermentation for the development of diacetyl or butter flavors."
Lyothier acknowledges that, "There is not as much focus on the process of micro-oxygenation in white wine as there is red wine, however it is a great tool, especially in wineries that have a large stainless-steel storage capacity and do not store on the lees because of reduction. Micro-oxygenation brings the winemaker closer to the wine because you need to check for microbial issues and for flavor development."
Jim Peck, senior research scientist with E&J Gallo Winery, began working with micro-oxygenation in 1995 after finding reduced flavors in some 4,000-gallon red wine tanks. Peck reports that, "There were remarkable differences between our treated tank and our control tanks. We eliminated reduction problems and had better clarity. We had softer tannins and a bit of age character. We found that micro-oxygenation in very large cooperage comes out with a much nicer product. There are a lot of benefits to it, but it also proceeds faster."
Peck addresses the downside of micro-oxygenation, explaining how, "On the third tank we did have Brettanomyces develop. The wine sat for about four months in the same tank that we'd used before for two months. There's a danger there: apply micro-oxygenation for too long and you can get wrecked." He continues: "I also did a tank where I thought if a little bit's good, what happens if you add a lot more? Of course, I oxidized the wine. One of the tanks that I'd over-treated made an amazing recovery and came out with some of the best characteristics."
One point Peck strongly advocates is that, "You cannot accelerate the aging process; you can only optimize it." He adds that, "Micro-oxygenation will make your life more difficult because you've got to watch it carefully, but it's a good method for controlling parts of your process."
As winemaker and president of Bonny Doon Vineyard in Santa Cruz, California, Randall Grahm calls himself a micro-oxygenation fanatic. "I discovered that if you keep oxidative grapes on the edge of reduction but not over the edge, you've made a very interesting wine." Grahm talks of the age-old technique of élevage, to which he claims French cellarmasters of yore paid close attention. "Micro-oxygenation enables you to master élevage, (part of which is) giving the wine the appropriate amount of O2 for its particular stage along its life." He adds that, "The reductive capacity of the wine is really one indication of its vitality. Certain varieties like Cabernet or Tannat have a strong reductive capacity."
The benefits of micro-oxygenation in wine are many, says Grahm. "It enables more volume and body, to make a softer, more ample wine. Certainly it enables one to master tannins. My new mantra is: ‘I will fear no tannin.' It helps the color stability and clarity of wine. It's effective at removing vegetal characteristics. It's a way of managing reduction. It's a way of keeping lees in wine without having systematic reduction.
"In a barrel, you've got oxidized conditions on the top of the barrel and reduced conditions on the bottom. Even though you still need to give the wine oxygen, it's taking up O2 and sulfur dioxide. If you can store wine in a large vessel with less headspace, you can probably minimize your sulfur dioxide take-up."
Grahm also cites a cost benefit. "You don't have to rack your wines as much. You can turn a large stainless or wood tank into--in a sense--a barrel by simply regulating the amount of O2 that you give it to mimic the O2 exchange of a barrel without moving from its vessel."
In a final analysis, Grahm reasons that micro-oxygenation is a gradual and gentle process. "I've always had the feeling that there are so many chemical reactions going on in wine, that the more gently you can effect these reactions, the less deleterious impact you have on the wine."
Clark Smith points to over-treatment as the biggest hazard of micro-oxygenation. In his experience, winemakers often do not stop the micro-oxygenation process when they should, which dries out the wine. "We call this snatching defeat from the jaws of victory," he smirks. "They promote over-polymerization and all this wonderful richness goes away. The only thing you can do then to save it is ultra-filtration. If it's not too overdone, you bring in some lees and coat the wine with a little richness."
"There's a tremendous amount of interest in micro-oxygenation," Clark concedes, "but we want to make sure people don't burn themselves." He quotes a Frenchman involved in regulatory study of micro-bullage who once commented that giving oxygen to winemakers is like giving razorblades to monkeys. "This stuff is pretty complicated to use," he surmises. "The benefits are amazing. The hardest part for us is putting up safety nets."
"I don't believe wineries can incorporate micro-oxygenation successfully without rethinking the whole winemaking process," Smith concludes. "Micro-oxygenation requires a lot of tasting. Anticipate at least three years and probably more like five to get underway from being a non-micro-oxygenation winery to a micro-oxygenation winery."
Micro-Oxygenation Versus Clique-age
Micro-oxygenation refers to treatment of wine--usually early in its life--by introduction of constant, low quantities of oxygen. Micro-oxygenation structurally transforms wine for increased mouthfeel, softer tannins, and enhanced color and aromas. Micro-oxygenation is done in tanks only, not barrels, which provide much less oxygen than a young wine can utilize for maximum benefits.
Since micro-oxygenation increases wine's reductive capacity, it does not reduce aging time and does not promote early release. If the wine is barreled immediately after micro-oxygenation, frequent rackings may be necessary to prevent the wine from becoming closed and hard. Or, clique-age may be used as an alternative.
Clique-age denotes the instantaneous introduction of a partial saturation of oxygen (usually about 25 percent) into wine during aging, using a dosing device including a remote control "cliqueur." Its purpose is to polish the wines by opening up the fruit expression, combating reductive flavors and accelerating the maturation of hard tannins. Clique-age is simply a more precise, less labor-intensive alternative to racking and may be done in barrel or tank.
Clique-age often diminishes the wine's reductive capacity and so may be useful in reducing maturation time to allow early release. It is not useful for building structure, diminishing vegetal aromas or enhancing color stability. Source: Vinovation,Inc.
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