1999 óta palackozunk borokat, de csak 2022-ben, egyik fehér PetNat-unknál tapasztaltuk azt a furcsa átmeneti jelenséget, amit a Bottle Shock című mozifimben is megemlítenek.
Esetünk
Gyönyörű egészséges termést szüreteltünk. Nem zúztuk, csak bogyóztuk a szőlőt, és azonnal préseltük. Majd a friss mustot acéltartályokba fejtettük. Nem kéneztük. Eközben nem tapasztaltuk, hogy a must színe változott volna. Az erjedés spontán, saját élesztőkkel rendben indult, mint mindig. A tartályban nem volt számottevő levegő. A tartályból való mintavétel egészséges illatú, ízű és színű bort mutatott. Az erjedés végén a megfelelő cukortartalomnál közvetlenül a tartályra csatlakozva, gravitációs úton, szivattyú és egyéb pincészeti beavatkozás nélkül közvetlenül a pezsgőspalackokba palackoztuk a majdnem kierjedt bort. A palackokat gitter boxokba fektettük. Nem tapasztatunk rendellenességet. Egy nap elteltével viszont furcsa színelváltozást vettünk észre, a bor színe sötétebbé vált, mintha barnatörés lenne. Egy-egy palackot felbontva az illata és az íze rendben volt. Két nap múlva is, három nap múlva is, egy hét múlva is. A szín viszont maradt sötét. Az igazi újjászületése a bornak kürölbelül 2 hónap múlva történt, amikor a szín teljesen visszaváltozott ez eredeti árnyalatába. És úgy is maradt. Minden szempontból makulátlan bort kaptunk vissza.
Minden borász ismeri ezt a jelenséget, amit palacksokknak neveznek, de a szakirodalom csak homályosan itt-ott említi. Úgy tűnik, a pontos hátterét még nem tárták fel. A legjobban összeszedett anyagot a palcksokk témáról alább bemásolom:
"The Mystery of Bottle Shock by Lance Cutler What causes it? What can you do about it? Though it's alarming, experts say the phenomenon is temporary and seems to resolve itself. Dick Arrowood told me a story. All the way back in 1974, which was Arrowood’s first vintage for Chateau St. Jean, he made a Select Late Harvest Riesling. It was incredibly delicious and loaded with wonderful botrytis character. He bottled right after fermentation, stopping around 7 percent residual sugar. He rough-filtered, sterile-filtered and bottled the wine as soon as he could. The wine was simply gorgeous. A month or two later the owners wanted to come up and taste all of the wines of that first vintage. Arrowood let them taste the wines in tank and barrel; but when he sampled one of the bottles of Riesling before they came up, it was terrible. It was sweet but without any botrytis character. It was dull and dumb, so he didn’t put that out for them to taste. Every time the owners came up to check the progress of the wine, he’d sample a bottle of Riesling by himself. It continued to be terrible, so he'd leave it out of the tasting. Finally, after about six months, the owners were up for another tasting, and they insisted on tasting the Riesling. Arrowood sent a guy into the warehouse with a forklift to get a pallet of the wine down, and the driver hit a case with the forks, breaking a bottle. Arrowood laughed at the memory: “The whole warehouse filled with that wonderful aroma of peach and apricot that goes with botrytis. I almost hugged the forklift driver because I realized the wine was back and I still had a job. Until that time, I had never heard of or experienced bottle shock. Now, after all these years, I still worry about it when I taste recently bottled wine, but I don’t panic like I did back then.” According to Arrowood, bottle shock certainly exists, but no one knows exactly what it is. He thinks it is probably caused by some sort of oxidative or reductive issue that occurs during filtration and/or bottling, but it could have to do with pressure or the mechanics of moving the wine. Arrowood said that in his experience, bottle shock diminished fruit and made the alcohol more apparent. It rendered the wine dumb and without charm. It was worse and lasted longer in white wines than red wines. Unfiltered red wines recovered in one to two months while white wines took more time, sometimes up to five or six months. He observed that the less that you did to the wine, the faster it recovered. Unfiltered wines recovered more quickly than filtered wines, but even wines that were bottled unfiltered went through it. “Whatever bottle shock is, we are fortunate that it doesn’t last. The wine does come back.” There is precious little information available about bottle shock or bottle-sickness even though almost every winemaker the world over is aware of it. Search the Internet and you will find dozens of references to “Bottle Shock” (the movie) but only one or two that address bottle shock, the wine condition. For the purpose of this article, we will define bottle shock as a temporary condition of wine characterized by muted or disjointed fruit flavors. Bottle shock can occur after wine transfers, filtration, bottling or even transport after the wine is in the bottle. Causes of Bottle Shock Bo Barrett from Chateau Montelena should know something about bottle shock. By now, surely everyone has heard how his 1973 Chateau Montelena Chardonnay won top prize at the infamous 1976 Paris tasting that pitted famous French Burgundies against California Chardonnays. As famously depicted in the movie “Bottle Shock,” that winning Chardonnay went through a serious bottle shock just before the tasting that changed the color. Barrett insists that legend aside, the wine did not suffer from bottle shock. Rather it suffered from a severe case of “pinking,” another temporary side effect of changing redox potential. Redox potential (or oxidation/reduction potential) is a measure of the wine's ability to be oxidized or reduced by either gain or loss of electrons. This can be related to the amount or lack of oxygen in the wine. Barrett has a rather organic explanation for bottle shock. “Wine sitting in a barrel receives oxygen that passes through the pores in the wood,” he explained. “The H20 and alcohol molecules interact with this back and forth passing of oxygen, happily. When you put that wine into a bottle, you change the equilibrium that it had in the barrel. The only oxygen it gets has to pass through the cork.” According to Barrett, this dramatic change from barrel to bottle also has a huge effect on Brettanomyces. Brett may be stable in a permeable barrel environment, but it gets decidedly unhappy in a bottle where the wine can't efficiently rebalance. Brett becomes an oxygen pig and starts leaving its signature “barnyard” aromas. Jeff McBride, vice president of winemaking at Benziger Family Wines, believes that the bottle shock phenomenon derives from several causes. Wine filtration is a major culprit. The tighter the filtration, the more “shocked” the wine becomes, especially for red wines, as tight filtrations actually remove some components (mostly larger structured phenolic and color compounds) that take time to recover through the oxidative process. This is affected by the type of filtration used. Diatomaceous earth (DE), pads and cross-flow filtration all affect the wine differently. According to McBride, “DE filtration, in conjunction with tight pad filtration, is analogous to pushing your face through a screen. Some ‘stuff’ is bound to stay on the screen, and it will take time to heal.” McBride also believes the timing of pre-bottling additions or fining, especially SO2 adjustments, can have a dramatic effect on the wine. “We have all seen what a hefty dose of metabisulfite (pre-bottling) can do to bleach a wine, especially Pinot Noir,” he explained. “The color does recover, but the time to recover is based on the chemistry of the wine and the size of the dose.” When it comes to bottling, McBride feels that O2 pickup at bottling can cause a shock, but the shock will be more permanent, and recovery to a starting-point aroma and flavor profile is not likely. If CO2 is added to achieve a desired “brightness,” the wine can seem disjointed until the components settle into a matrix. Trying to determine how filtration influences bottle shock, we spoke with Stefano Migotto. Migotto ran his father’s winery in Northern Italy for 12 years. He worked in California wineries for several years before starting Winetech, a company that provides mobile wine filtration services, in 1998. Migotto is convinced that bottle shock is real and does everything he can to minimize its appearance after he works with a client's wine. Migotto says that the primary culprit that causes bottle shock is oxygen. The more oxygen picked up by the wine during any wine processing procedure, the more likely that wine will show signs of bottle shock and the more severe it will be. After spending 15 years as a filtration specialist, Migotto believes how well a wine is treated during its production cycle is key to the amount of bottle shock it will go through, so a big part of his job is to minimize O2 pickup during his filtrations. “I have come to believe that cross-flow filtration is the best way to filter wine,” Migotto declared. “DE filtrations are particularly difficult, because the actual DE is porous and full of air. No matter how adept the operator, DE filtration will expose the wine to significant amounts of O2. Filter pads can have similar issues, and the ability and training of the operator have a big influence. Then, of course, both DE and filter pads have a distinct flavor that can affect the wine.” Cross- flow filtration, performed using good equipment by an experienced operator, doesn’t introduce as much O2 to wine, according to Migotto. Minimizing Bottle Shock Zack Scott is the assistant president of Scott Laboratories, a company developing and representing products, including fermentation goods, filtration media, equipment, packaging products and laboratory services, so they have a handle on virtually every winemaking task. Scott said that when it comes to bottle shock, most of his clients want to know what they can do to minimize it and how long they have to wait to get that wine to market. Scott feels that several different factors contribute to bottle shock. Oxygen pickup, during filtration and bottling, is one culprit, but ingredients added to wine are another, especially SO2. He points out that any type of filtration “squeezes” the wine and affects the colloidal matrix of the wine. Comparing unfiltered wine with the same wine immediately after filtration confirms a clear loss of varietal character; but as the colloids resume their shape, the wine will come back. He agrees with Migotto that cross-flow filtration has the least disruptive effect on wine, given the various filtration choices. “S02 management has a big influence on what we perceive as bottle shock,” said Scott. “Wineries are in a perpetual drive to maximize the efficiency of SO2 use, but any addition has a carryover effect. It is very expensive for high-volume wineries to have thousands of cases of wine sitting in warehouses, waiting to recover from bottle shock. Smaller SO2 additions at bottling might help allow for an earlier release of that wine. Of course, using less SO2 at bottling carries higher risks of spoilage or oxidation.” Scott emphasizes that using the best equipment for filtration and bottling, along with top-flight packaging and well-trained personnel, limits the wine’s exposure to oxygen, thus reducing the effects of bottle shock. Small considerations, like adjusting the fill height, depending on the temperature of the wine, to allow for expansion or contraction, can have major implications for bottled wine in terms of oxygen pick-up. José Santos, president of Enartis Vinquiry, feels that all of the treatments and procedures involved in getting wine ready to bottle, like filtration, wine transfers, CO2, SO2 and nitrogen, all contribute to bottle shock because they change the redox potential of the wine. As an example, an SO2 addition can suppress varietal character and diminish complexities; but because S02 is more oxidative than wine, oxidation will occur on SO2 more readily, and it will eventually bind up and cease its “masking” effect. Santos said, “Filtering is the biggest problem because it changes the colloidal makeup of the wine, which affects our perception of texture, mouthfeel and aromatics. Over time, the colloids will rearrange themselves and return to a close approximation of where the wine started.” Gordon Burns, founder of ETS Laboratories, points out that there is no one cause for bottle shock. There are many root causes, and some of them are still not known. He believes there are two main culprits when it comes to bottle shock. The first is rapidly changing the redox potential of the wine, which impacts the aroma and texture of the wine. Second is the filter media, which influences the colloidal composition of the wine. “Simply put,” Burns explained, “colloids are the stuff that sticks together. Filtration, whatever the media, dissembles those colloids, and they take time to re-form.” Burns also reveals that wine stability plays a large part in bottle shock. If the wine is stable and the free SO2 is stable, then the bottle shock effects will be lessened. That means that late blends, late filtrations and late SO2 additions are all likely to increase bottle shock and cause it to last longer. Winemakers who monitor SO2 levels more frequently, making smaller additions and maintaining steady SO2 values, end up with more stable wines, which are more resistant to bottle shock. What Researchers Say Dr. Andrew Waterhouse, wine chemist and professor of enology at UC Davis, is an internationally recognized wine chemist whose research focuses on phenolic compounds. In the area of wine quality, his current interest is in the effect of oxidation on wine chemistry and how this oxidation affects important quality parameters of wine, such as taste and color. He admits that little research has been done on bottle shock, so not a lot of information exists. He supposes the transitory and reversible nature of the process has meant that most winemakers do not view it as a problem. Dr. Waterhouse does have a hypothesis. He believes that when wine is bottled, it goes from a tank where it has been anaerobic for months, through a process that introduces oxygen. The amount varies widely, but with a well-run modern bottling line, you can limit dissolved oxygen to about 1 mg/L. There is also oxygen in the headspace, and that can equal or exceed the total oxygen in the liquid. With a poorly managed bottling, you can end up with near saturation (the amount obtained by fully exposing the wine to air) of about 8 mg/L. If you taste the wine immediately, it will taste just like the wine from the tank, but over an hour or so, as the oxygen reacts with the wine, the oxidation products will change the flavor, just like when wine is decanted. However, the process continues far longer and with larger changes over several days. Dr. Waterhouse explained, “One of the effects of this injection of oxygen is to produce some aromatic aldehydes, in particular, acetaldehyde from ethanol. The amount of oxygen that can react over one to four weeks could produce enough of these aldehydes to impact aroma. So, during this time, the aldehydes can mask fruity and other aromas. As these aldehydes are themselves reactive, they combine with other chemicals in the wine, such as the phenolics, and they ‘disappear,’ restoring the wine to almost its original aromatic state.” Dr. Waterhouse also believes that oxidation will certainly decrease other aromatic substances slightly. Since white wines have much lower levels of phenolics, these wines will start to accumulate the aldehydes, after a moderate amount of oxidation has occurred, while reds, with much more phenolics, are protected through more oxidation. Dr. Roger Boulton, also from UC Davis, is convinced bottle shock is caused by something else. Dr. Boulton studies the chemical and biochemical engineering aspects of winemaking. His work involves fermentation and reaction kinetics and the physical and chemical stability of wines. His current research involves the phenomenon of co-pigmentation, especially in red wines, as well as fermentations involving juice composition and sulfide formation. Dr. Boulton believes that the condition known as bottle shock is caused by a long persistent concentration of peroxide. It occurs in wine several days or maybe even weeks after the initial exposure to oxygen. Typically, people blend, filter or transfer wine and get oxygen pick-up a few days or weeks before bottling. The O2 will be gone in a matter of days, but there will be peroxide in the bottle for the next three or four weeks. The peroxide does two things: it slowly oxidizes the wine, but more importantly, it attacks what we would call varietal character in wine. “We've always known that peroxide was the major damaging component, not oxygen, and the real damage of peroxide is to varietal character,” explained Dr. Boulton. “These compounds that create varietal character are incredibly small in concentration (parts per trillion) and are reactive with respect to peroxide. It isn’t about phenyl oxidation, and it isn’t about SO2; it's about peroxide’s slower reaction, which is why it takes so long and persists.” According to Dr. Boulton, what we have come to know as bottle shock occurs due to peroxide residing in the wine as a result of oxidation from earlier wine movement. For example, racking wine from barrels or transferring from tanks might introduce oxygen to the wine, but the oxygen will be gone fairly soon. Peroxide persists for a much longer time, often weeks. When the peroxide affects the radicals in these very tiny compounds that create varietal character, we assume it is the bottling that causes it. In fact, it dates back to the oxygen pick-up from racking and transferring the wine that occurred weeks earlier and created the peroxide in the first place. Moreover, presence of peroxide with ethanol would typically lead to acetaldehydes, but free SO2 hides that effect. Since most wineries bump SO2 levels before and during bottling, this “evidence” of the presence of peroxide is masked. It’s as if residual peroxide causes a temporary bruise to varietal character, one that recovers over time. Dr. Boulton suggests a simple experiment to demonstrate the phenomenon. “Take some wine and, using a control, taste that wine against a sample to which some hydrogen peroxide has been added. Cover the glasses for a while and then smell and taste the samples. You will see that the varietal character is greatly reduced, just as it is with what we call bottle shock. The change will likely occur faster in wines with lower SO2 levels.” Boulton added, “There is no experimental data to verify this. It's the kind of stuff we would never get a grant for because everyone thinks they know exactly what it is, but they are wrong. The industry people certainly don’t want to fund a study that proves them wrong, so they just go on believing that oxygen pick-up causes bottle shock.” What Happens During Shipping? All of the various experts have an explanation for the cause of bottle shock. It may be due to oxygenation from wine transfers, filtration or bottling itself. It is likely affected by the use of CO2, SO2 and nitrogen. The introduction of oxygen into the wine may cause a build-up of peroxide that requires time to resolve itself. These are plausible theories and help explain bottle shock but what about the type of bottle shock that occurs from transporting wine? Once wine has been bottled, it is generally warehoused for a period of time before sale. Surely, the wine will have recovered from bottle shock before the wine arrives at the distributors. Yet many of us have experienced a type of bottle shock from bottles trucked across the country or shipped from Europe or South America. We can sometimes see the same result, taking wines from our cellars along with us on vacation trips. The wines seem to lose their fruity, varietal character. They become disjointed. Alcohol and tannic astringency seem more prominent. This bottle shock also seems temporary, and the wine eventually recovers. When asked about this occurrence, most experts cited temperature during shipping as the possible culprit. Santos pointed out that all chemical reactions occur faster at higher temperatures; so if shipped wines heat up in railcars or containers, compounds interact more quickly. In effect, these faster reactions mimic aging. It's why we try to store wines at cooler temperatures. Boulton is more specific, “This is due to additional oxygen uptake while wines heat up and cool down, which expels headspace gas and draws in air (20 percent oxygen). This brings in only micro-liters each cycle but often goes on for two weeks to two months, depending on transport distance and carrier type.” A Phenomenon that Resolves Itself Talking about bottle shock, Dick Arrowood portrayed it this way, “Put 10 winemakers in a room and you'll come up with 15 different theories.” He illustrates a good point. Most winemakers assume they know what is going on with their wines, all of the time. If they are not exactly sure, then they use their experience and logic to formulate a theory. Virtually, all bottle shock theories begin with oxygen as the culprit. Many winemakers have come to believe that oxygen is critical during fermentation. Others believe oxygen is helpful during barrel aging as evidenced by the traditional racking of barrels or the more current use of micro-o0x, but most winemakers try to restrict the introduction of oxygen into their wines as they remove it from barrels or transfer it from tanks to prepare for bottling. Bottle shock is a phenomenon all of us have experienced and have to live with. If winemakers had to watch their lovely wines lose varietal character, become disjointed and go out of balance permanently, then bottle shock would be the most researched phenomenon in all of winemaking. Because it is temporary and seems to resolve itself, there has been precious little investigation as to the causes and effects. After researching the subject, I think the best summation of this bottle shock study comes from Stefano Migotto talking about winemaking in general, “We have done so much research that we think we know a lot, but in the end, we have no idea.” WBM"