Ok so the title of this post is obviously sarcasm, but there is some truth to it. Especially in the Willamette Valley. Wine grape growing in Oregon is a challenge. The single biggest factor to affect the quality of the wine is the quality of the grapes in it. It is an often repeated saying, but good wine is made in the vineyard. That is not to put the entirety of the growing season on the vineyard manager though, weather is what determines the baseline of a growing season. Not everyone in Oregon will choose to use organic chemicals, or to machine harvest, but every region will be subjected to similar weather patterns. Freezing in April, rain in July, rot in October, these are all things that can and will happen to event the most manicured vineyard.
Winemakers typically track 4 things during maturation of grapes; the pH, titratable acidity, degrees Brix, and eventually the taste and feel of the berry. The challenge in Oregon winemaking and grape growing is hitting your picking window perfectly. A grapevine is intentionally stressed, a lot of vineyards in Oregon choose not to irrigate and instead let the taproots do the work. This is because the happiest grapevine is not necessarily the best wine producing one. The plant must be scared into thinking conditions aren't ideal and reproduction is a necessity. This causes a very thirsty plant by the end of ripening.
Winemakers must base there pick time off three factors, physical ripeness, crushing schedule (big wineries must sometimes pick early or late simply because they have no other time to process the fruit), and weather. No one wants the weather to determine the pick time because then the winemaker is out of control and must begin to gamble. Will more rain come? The second rain hits the ground it is absorbed by the vine and sugar and acidity levels begin to dilute. This will set off a chain reaction of actions and decisions which are designed to mitigate the fact that we live in a very hard place to grow grapes.
Why would dropping sugar levels be concerning to a winemaker? Yeast ferment sugars into carbon dioxide and ethanol, less sugar means less alcohol, more sugar means more alcohol. We try and achieve a balance between acid, sweetness, and bitterness in the wine. Bitterness can be controlled by the alcohol level, and there is a base alcohol that needs to be present in order for the wine to taste like a wine. It is therefore essential that we achieve a minimum sugar concentration within the grape juice before it becomes wine.
This post is geared more towards American wine in general, so California must enter the discussion. Some of the more revered regions in California enjoy completely different weather patters. While our cool and mild climate is conducive to Pinots, the dry heat and long summers of California are great for bigger reds like Cab and Syrah. Californian winemakers have the opposite problem that we do: too much sun. This is reflected in laws about what can be added to grape must. In Oregon, it is legal to add sugar directly to the must the increase degrees Brix before fermentation. In California, they must do the opposite and dilute the must down to a more agreable level (both for the yeast and the consumer). Huge, ripe crops are almost a guarantee in California, and part of the reason that Napa vineyard land is some of the most expensive in the world.
So why does all of this matter?
I received a comment to a post talking about giving up on American wine due to our usual problem: too much excess. Over sweet, and high alcohol were some of the typical descriptors used to describe American wine, and that hurts. I do not feel that this problem is linked to American wine in general, just certain regions and certain techniques that have been glorified to a point of distaste. I also have faith in economics, if American wine was being held back by over ripening and excess sugars, the market should have naturally compensated. Perhaps it is beginning to?
In most of the regions in Oregon, 15% alcohol is simply not achievable in a normal year. Based on recent trends, we are more likely to be under ripe. This leads to a berry which is higher in acid and lower in sugar. Our pinot gris should have a sweetness to it, but what really drives it home with consumers is the well balanced acid. That is no accident, we use the tools, or terroir, that the region gives us. So if you are in search of a different style of wine, I would recommend looking at a different region. As the industry grows winemakers are trying to explore every possible climate and soil they can offer to their vines, and with some excellent results.
Monday, August 22, 2011
Gone Country...
Sorry for the delay in posting, I found myself at the Willamette Country Music Festival this weekend and the 3G was too overloaded to write anything. I have plenty of ideas though, more to come...
Tuesday, August 16, 2011
The Ice Age is Over
If there is one machine that will truly make my life easier, it is the electrodialysis filter that will soon be showing up on our loading dock. This filter eliminates the cold stabilization process currently used to prepare wine for bottling. In large production facilities, it is essential to cold stabilize wine. Cold stabilization refers to the process of removing excess tartaric acid as its salt, potassium hydrogen tartrate (KHT). The acid crystal is considered undesirable in young wines by American consumers, and we make quite an effort to ensure the chance of them forming in a young bottled wine is removed.
At wine pH, most acids will be at least partially deprotonated. In other words, they will exchange a hydrogen with a molecule of water and temporarily be left with a negative charge. This process happens countless times per second, but averaged over time the negative charge is available for reaction. When a potassium ion, which is positively charged, meets the negative charge on the tartrate, a stable ionic bond is formed and the molecule precipitates (becomes solid). This happens naturally with aging, but there are ways to accelerate the process. The usual way takes advantage of solubility.
Temperature greatly affects solubility. As temperature falls, so does solubility. Temperature is related to molecular vibration, more simply the space created between molecules by like-charge repulsion. The majority of molecules in wine are water molecules, as they are cooled their vibration slows and they move closer together. This literally squeezes out molecules which are unable to fit between the lattice. Modern wineries use a glycol cooling system to lower wines below the freezing point of water and precipitate out KHT molecules to settle at the bottom of the tank. If they do not perform cold stability and bottle soon after harvest, tartaric acid crytals will appear in the wine bottle. Additionally, we add an excess of KHT to the tank once it has cooled to provide a substrate for additional KHT precipitation. The process takes somewhere around two weeks to a month, during which time thick ice coats form on the jackets used to cool the tank.
Once cold stability is confirmed through a lab conductivity test, the wine is ready for filtration. It cannot be allowed to warm before filtration or the KHT crystals will dissolve back into solution. Our method of choice is a crossflow filter. At 8 gallons per minute it can be quite a process to filter just our Pinot Noir, and during the summer it is taxing to chill large tanks to the necessary temperature. That is why I am so excited for our new technology.
ED filtering is not new, but it is still very expensive to get started. However, the savings start paying for it immediately. Electrodialysis filters use an electric charge coupled with ion selective filters to attract potassium ions out of the wine. By removing excess potassium ions and some tartaric acid ions, the wine not longer has the chemical potential to precipitate tartrates in the short term. It is inevitable that it will happen eventually, but the amount is usually small and at that point, desired by the consumer as a show of maturity.
The filter does not require the wine to be cooled, making it a huge power saver. The crossflow filter can be run at cellar temperature as well, which speeds it from 50-100%. The filter also allows us to cut down the time required to prepare a wine for bottling. At the speed we are expanding every second counts. To me, this machine made absolute sense as a purchase. It saves us money, time, lab analysis, and me getting hit in the head by falling ice jackets. Oh, and I might just sleep a little better this year too.
At wine pH, most acids will be at least partially deprotonated. In other words, they will exchange a hydrogen with a molecule of water and temporarily be left with a negative charge. This process happens countless times per second, but averaged over time the negative charge is available for reaction. When a potassium ion, which is positively charged, meets the negative charge on the tartrate, a stable ionic bond is formed and the molecule precipitates (becomes solid). This happens naturally with aging, but there are ways to accelerate the process. The usual way takes advantage of solubility.
Temperature greatly affects solubility. As temperature falls, so does solubility. Temperature is related to molecular vibration, more simply the space created between molecules by like-charge repulsion. The majority of molecules in wine are water molecules, as they are cooled their vibration slows and they move closer together. This literally squeezes out molecules which are unable to fit between the lattice. Modern wineries use a glycol cooling system to lower wines below the freezing point of water and precipitate out KHT molecules to settle at the bottom of the tank. If they do not perform cold stability and bottle soon after harvest, tartaric acid crytals will appear in the wine bottle. Additionally, we add an excess of KHT to the tank once it has cooled to provide a substrate for additional KHT precipitation. The process takes somewhere around two weeks to a month, during which time thick ice coats form on the jackets used to cool the tank.
Once cold stability is confirmed through a lab conductivity test, the wine is ready for filtration. It cannot be allowed to warm before filtration or the KHT crystals will dissolve back into solution. Our method of choice is a crossflow filter. At 8 gallons per minute it can be quite a process to filter just our Pinot Noir, and during the summer it is taxing to chill large tanks to the necessary temperature. That is why I am so excited for our new technology.
ED filtering is not new, but it is still very expensive to get started. However, the savings start paying for it immediately. Electrodialysis filters use an electric charge coupled with ion selective filters to attract potassium ions out of the wine. By removing excess potassium ions and some tartaric acid ions, the wine not longer has the chemical potential to precipitate tartrates in the short term. It is inevitable that it will happen eventually, but the amount is usually small and at that point, desired by the consumer as a show of maturity.
The filter does not require the wine to be cooled, making it a huge power saver. The crossflow filter can be run at cellar temperature as well, which speeds it from 50-100%. The filter also allows us to cut down the time required to prepare a wine for bottling. At the speed we are expanding every second counts. To me, this machine made absolute sense as a purchase. It saves us money, time, lab analysis, and me getting hit in the head by falling ice jackets. Oh, and I might just sleep a little better this year too.
Monday, August 15, 2011
Molecular Sulfur
One of the most valuable things I have learned since beginning work in the industry has been the importance of doing things today. Oxidation doesn't wait, Brett doesn't wait, and we as winemakers should not either. This should be a guiding principle for winemakers when it comes to the use of sulfites. I say sulfites, not sulfur dioxide, to emphasize something I run into in Oregon a lot. There is a general lack of knowledge about the role of sulfites and what is actually happening when we add sulfites to a wine.
One of my favorite litmus tests for new wineries and winemakers is asking about their sulfur program. I would love to report that I often learn new facts about how other wineries maintain sulfur levels, but it simply isn't true. While we may not have the capital and resources that some of the large California wineries have, I believe there is still no excuse to be lazy or ignorant when it comes to the knowledge and testing of sulfites. But astonishingly there are plenty of winemakers who seem to be.
If you take one thing away from this post, realize this. The effectiveness of sulfur dioxide is directly related to the concentration of sulfites and the pH of the wine. A good winemaker would never let a lab get away with reporting just a free sulfur number, the pH and free sulfur should always be reported together. Sulfites exist as three distinct compounds at wine pH (Ok, 2 unless you are majorly messing up). There is the very familiar molecular sulfur, SO2, bisulfite anion HSO3-, and the sulfite anion SO3=. At 0 pH it will exist as almost 100% molecular SO2. When the pH gets to ~4.5 the species is ~100% HSO3-. The behavior of HSO3-/SO3= is very similar.
A quick chemistry aside:
We chemists rely on changing the polarity of chemicals as a way to get them to elute from a solvent. The aeration-oxidation test for free sulfur takes advantage of this principle. By adding excess phosphoric acid the pH is driven down to maximize the amount of molecular SO2 present. Molecular SO2 is very volatile, while the deprotonated forms will not come out of water easily. In addition there is a very nice oxidation reaction that takes place between SO2 and H2O2, making the molecular form the most easy to capture and quantify. So what we are doing with aeration-oxidation is converting all of the sulfite species to molecular sulfur dioxide, eluting the mSO2 into peroxide, and then titrating. This is a very convenient way to measure the amount of molecular sulfur at an artificial (0) pH, but it tells us nothing about the amount of molecular sulfur at wine pH.
This is why the concerned winemaker should always ask for a pH. The most effective antimicrobial form of sulfite is molecular SO2. I have heard many different concentrations, but in general we keep wines in the cellar at 0.8 ppm molecular SO2. Bear in mind that we make a lot of cold climate Pinots, so our pH is usually below 3.55 or so. Our lowest is a Riesling clocking in at 2.95. To be adequately protected, the Riesling would be kept at 12 ppm free, and the 3.55 Pinot at 46 ppm free. This opens up a huge discussion on the winemaker's decisions around bottling, but that is a post for another day.
It is also worth nothing that pH can be a limiting factor for sulfur. A Cabernet with a pH of 3.80 simply will not drink well with 79 ppm free. However, that is no excuse to be lazy. One must lab trial and come up with a level that balances detectability with protection; having too much sulfur by 15 ppm is a lot easier to deal with then having to remedy early and excessive oxidation with the possibility of a host of spoilage organisms.
Chemicals are very valuable tools. SO2 is a wonder-chemical to a winemaker. Anti-oxidant, anti-oxidase, and anti-microbial; it is a perfect tool for the long and short term storage of wine. And when it is used correctly, the consumer will enjoy the wine exactly as it was intended. If there is anything valuable to be learned in this post, it is that fact. Good SO2 management makes good wine.
One of my favorite litmus tests for new wineries and winemakers is asking about their sulfur program. I would love to report that I often learn new facts about how other wineries maintain sulfur levels, but it simply isn't true. While we may not have the capital and resources that some of the large California wineries have, I believe there is still no excuse to be lazy or ignorant when it comes to the knowledge and testing of sulfites. But astonishingly there are plenty of winemakers who seem to be.
If you take one thing away from this post, realize this. The effectiveness of sulfur dioxide is directly related to the concentration of sulfites and the pH of the wine. A good winemaker would never let a lab get away with reporting just a free sulfur number, the pH and free sulfur should always be reported together. Sulfites exist as three distinct compounds at wine pH (Ok, 2 unless you are majorly messing up). There is the very familiar molecular sulfur, SO2, bisulfite anion HSO3-, and the sulfite anion SO3=. At 0 pH it will exist as almost 100% molecular SO2. When the pH gets to ~4.5 the species is ~100% HSO3-. The behavior of HSO3-/SO3= is very similar.
A quick chemistry aside:
We chemists rely on changing the polarity of chemicals as a way to get them to elute from a solvent. The aeration-oxidation test for free sulfur takes advantage of this principle. By adding excess phosphoric acid the pH is driven down to maximize the amount of molecular SO2 present. Molecular SO2 is very volatile, while the deprotonated forms will not come out of water easily. In addition there is a very nice oxidation reaction that takes place between SO2 and H2O2, making the molecular form the most easy to capture and quantify. So what we are doing with aeration-oxidation is converting all of the sulfite species to molecular sulfur dioxide, eluting the mSO2 into peroxide, and then titrating. This is a very convenient way to measure the amount of molecular sulfur at an artificial (0) pH, but it tells us nothing about the amount of molecular sulfur at wine pH.
This is why the concerned winemaker should always ask for a pH. The most effective antimicrobial form of sulfite is molecular SO2. I have heard many different concentrations, but in general we keep wines in the cellar at 0.8 ppm molecular SO2. Bear in mind that we make a lot of cold climate Pinots, so our pH is usually below 3.55 or so. Our lowest is a Riesling clocking in at 2.95. To be adequately protected, the Riesling would be kept at 12 ppm free, and the 3.55 Pinot at 46 ppm free. This opens up a huge discussion on the winemaker's decisions around bottling, but that is a post for another day.
It is also worth nothing that pH can be a limiting factor for sulfur. A Cabernet with a pH of 3.80 simply will not drink well with 79 ppm free. However, that is no excuse to be lazy. One must lab trial and come up with a level that balances detectability with protection; having too much sulfur by 15 ppm is a lot easier to deal with then having to remedy early and excessive oxidation with the possibility of a host of spoilage organisms.
Chemicals are very valuable tools. SO2 is a wonder-chemical to a winemaker. Anti-oxidant, anti-oxidase, and anti-microbial; it is a perfect tool for the long and short term storage of wine. And when it is used correctly, the consumer will enjoy the wine exactly as it was intended. If there is anything valuable to be learned in this post, it is that fact. Good SO2 management makes good wine.
Friday, August 12, 2011
The Importance of Skepticism
What do you do when an outside lab has numbers which are completely at odd with in-house analysis? We use a certain unnamed enological lab which is accredited by national and international organizations alike. These serve to guarantee the analysis method and results to national watchdogs like the TTB and to smooth over the international sale of wine. For example, the US and Canada agree on an analysis method for something such as residual copper level, and trade is smoothed because only the export country has to perform the analysis. There is a lot of money and trust riding on the analysis of these labs; their results directly influence both the sale and treatment of wine. So how do we keep them honest?
Our problem relates to free SO2 testing. We perform the tried and true aeration-oxidation method, and have been doing so for some time. Now I am perfectly aware that our results are somewhat relative no matter what, but there is simply no way we should be more than 25% off of what an outside lab gets. So when our export analysis showed 12ppm SO2, and our in-house result was 22ppm, flags were raised. However, despite all of the credentials that our outside lab has I immediately knew they were in error.
I didn't feel this way because I had excess pride or a strong gut feeling, I felt this way because we make a significant effort in the lab to track our own precision and accuracy (precision is a measure of repeatability, accuracy is a measure of how close we are to the real value). At least once a week each tech in our lab runs 4 FSO2s on our standard twice. We keep all of this data and use it to assess the P&A of the analyst and setup alike. For example, we use 4 round bottom flasks and each is carefully tracked to make sure there is not any determinate trends between flasks. This data is as valuable as any test performed on an unknown. All of the work we do to test our known standards is what gives legitimacy to the work on our unknown samples. If you cannot consistently test a known standard to an acceptable degree of error, there is no way you can confidently say your have the correct value for an unknown sample. This is the underlying truth in a lab, and something that simply can't be ignored by the manager.
It was with all of this evidence that we had no problem calling our outside lab and telling them quite simply that they were wrong. To prove it, we sent a sample bottle from the same case to the original testing lab, a secondary outside lab, and repeated the analysis for a third time in our own lab. Our lab and the secondary lab were within 2 ppm of each other, in my experience this is basically an identical result. The original outside lab, after we confronted them with their results, agreed to retest for free and upon doing so came back with a result of 20ppm. They use flow-injection analysis for FSO2 tests, and I'd magine that they do hundreds of tests a day. The focus is quantity, not quality, and unfortunately the burden of proof falls on the lab requesting the analysis, not the "credible"outside lab doing the test.
Science is skepticism, and always will be. This experience highlighted a glaring hole in my thinking as a scientist. We have always operated under the assumption that our outside lab was infallible and not run by humans. But this is simply not true, while they have the ability to analyze and report numbers, they don't know how those numbers match up with past analysis. If our lab gets an unexpectedly low result, they always retest and confirm before reporting. They have the data in the lab to match with their current result. And I'm not implying that we go fishing for the numbers we want, but if a 10ppm sulfur hit in the cellar leads to a lower result than the one we got before the hit, we would call that result suspicious and retest. Objectivity is one of the great features of doing analysis at the winery, and this incident really drove that home. Oh and for the rest of the wineries who have been getting low results from this same lab, you're welcome;) As my economist brother pointed out, we are all compl-E-mentary.
Our problem relates to free SO2 testing. We perform the tried and true aeration-oxidation method, and have been doing so for some time. Now I am perfectly aware that our results are somewhat relative no matter what, but there is simply no way we should be more than 25% off of what an outside lab gets. So when our export analysis showed 12ppm SO2, and our in-house result was 22ppm, flags were raised. However, despite all of the credentials that our outside lab has I immediately knew they were in error.
I didn't feel this way because I had excess pride or a strong gut feeling, I felt this way because we make a significant effort in the lab to track our own precision and accuracy (precision is a measure of repeatability, accuracy is a measure of how close we are to the real value). At least once a week each tech in our lab runs 4 FSO2s on our standard twice. We keep all of this data and use it to assess the P&A of the analyst and setup alike. For example, we use 4 round bottom flasks and each is carefully tracked to make sure there is not any determinate trends between flasks. This data is as valuable as any test performed on an unknown. All of the work we do to test our known standards is what gives legitimacy to the work on our unknown samples. If you cannot consistently test a known standard to an acceptable degree of error, there is no way you can confidently say your have the correct value for an unknown sample. This is the underlying truth in a lab, and something that simply can't be ignored by the manager.
It was with all of this evidence that we had no problem calling our outside lab and telling them quite simply that they were wrong. To prove it, we sent a sample bottle from the same case to the original testing lab, a secondary outside lab, and repeated the analysis for a third time in our own lab. Our lab and the secondary lab were within 2 ppm of each other, in my experience this is basically an identical result. The original outside lab, after we confronted them with their results, agreed to retest for free and upon doing so came back with a result of 20ppm. They use flow-injection analysis for FSO2 tests, and I'd magine that they do hundreds of tests a day. The focus is quantity, not quality, and unfortunately the burden of proof falls on the lab requesting the analysis, not the "credible"outside lab doing the test.
Science is skepticism, and always will be. This experience highlighted a glaring hole in my thinking as a scientist. We have always operated under the assumption that our outside lab was infallible and not run by humans. But this is simply not true, while they have the ability to analyze and report numbers, they don't know how those numbers match up with past analysis. If our lab gets an unexpectedly low result, they always retest and confirm before reporting. They have the data in the lab to match with their current result. And I'm not implying that we go fishing for the numbers we want, but if a 10ppm sulfur hit in the cellar leads to a lower result than the one we got before the hit, we would call that result suspicious and retest. Objectivity is one of the great features of doing analysis at the winery, and this incident really drove that home. Oh and for the rest of the wineries who have been getting low results from this same lab, you're welcome;) As my economist brother pointed out, we are all compl-E-mentary.
Thursday, August 11, 2011
The Economy is Screwcapped
The fall of financial markets in 2008 led to several significant changes at our winery. While the reduction of cash flow was certainly one of them, it was the creation of a new brand and market which amazed me most. We are by no means a super premium winery, but our target market used to consist of a lot of over $20 a bottle drinkers. To stay competitive in our rapidly shrinking market, we had to come up with a way to make the same quality wine at a cheaper price. At first, this may seem like an oxymoron, but with a sharp decrease in demand the prices for grapes fell significantly. This was the first hurdle to overcome, and a relatively easy one. The real challenge began after the grapes landed on the crush pad.
Wine making can be oversimplified into two facts: the juice must be made into wine, and that wine must be packaged. The wine does not care what bottle it ends up in, or what the label looks like. In creating a good drinkable wine at a lower price point, the packaging choices were obvious. What the wine does care about is the closure in which it resides under. With cheaper packaging comes the decision of cork or screwcap. Before the inception of this brand, I used to scoff at screwcaps. To the inexperienced drinker, it is often a sign of low quality, reductive wines. But with the taming of the screw comes the respect of the screwcapper (in the words of Ferris Bueller, 'if you have the means I'd highly recommend picking one up'). A screwcap is a beast of a different nature, and as we learned more about the closure it taught us much more about the nature of wine in this closure.
Now for some chemistry. Thanks to the rise of the screwcap, we have a plethora of 3 letter acronyms in the bottling room. They mostly refer to the relationship of oxygen and wine, and the efficiency of oxygen in passing by the closure. In a very well known wine movie, there is a scene describing a bottle of wine as a living thing, something that matures and changes with age. This is certainly true, but not all change is good. The 'life' that drives the wine is a complicated and reversible matrix of chemical reactions involving the 'redox,' or reduction/oxidative potential of the wine. I would love to give a gen chem lesson right here, but to keep things simple I will use the acronym that I was taught. OIL RIG - oxidation is loss, reduction is gain. This refers to electron movements between molecules within the wine. To be oxidized is to lose electrons (there is a definied number for each molecule in each oxidation state). Some molecules want electrons more than others, and this difference in affinity gives rise to cascading chemical reaction. That is to say there is a strong interconnection between A and D when A reacts to form B, B reacts to form C, and C reacts to form D. What stops that reaction from reaching equilibrium and hence ceasing to age? OTR, or oxygen transmission rates. Each modern closure lets a predictable amount of oxygen react with the wine during aging ( perhaps this gives rise to bottle shock? oxygen is introduced during bottling and then the wine is closed. it would seem to me a macro-equilibrium would need to take effect, thus explaining the change in taste after bottling).
I could write for days about the reactions of oxygen and wine, but for now I want to concentrate on the reductive qualities associated with a screwcap. The approach to winemaking must consider the closure which the wine will end up under, and the period of time the winemaker has to stabilize the redox state of the wine.
Wines begin their life with a huge desire for oxygen. Yeast have a hunger for oxygen, and if they do not get it poor fermentation and off aromas will develop. After primary fermentation, the wine still needs a substantial amount of oxygen to aid in the aging process (like every rule, there are exceptions to this. and also I am thinking WV pinots here). Anyone who has opened a tank to the smell of deep cooked meat and earth has seen this first hand. An excellent indicator of reduction in the early stages of winemaking is the formation of hydrogen sulfide, H2S. H2S is in a redox equilibrium with SO2 (or O2S of you would prefer). Organic chemistry simplifies redox relationships to say a molecules' oxidation state changes when the number of oxygen bonds change. This is a firsthand example. In a reduced environment, sulfur easily exchanges its oxygen molecules for two hydrogen molecules. Upon introducing excess oxygen, H2S is oxidized from its farty smell back to the wonderfully choking SO2 stench. Cellar operations during harvest use this principle, the winemaker should splash rack in order to provide the necessary oxygen and age the wine. The oxygen consumption potential of a young red wine is huge, oxygen is in high demand and is broken down from atmospheric dioxygen into individual molecules which fit like puzzle pieces in the chemical matrix. As the wine is allowed to use oxygen where it is needed, the consumption potential begins to fall. This is where the winemaker must make educated decisions about the timing of bottling under screwcap (a post for another day...the best time to treat H2S and mercaptans is in a very reductive state, more to come...).
A major concern when bottling under screwcap is the presence of disulfides and mercaptans (thiols). The two are closely related. A mercaptan is the sulfur containing analog of an alcohol. For example, methanol has the formula CH3OH. Methanethiol has the formula CH3SH. Sulfides have a unique property of forming a disulfide bridge. The two sulfur atoms can form a covalent bond and stick together in the formula CH3SSH3C. This will occur in a reductive environment and is of significant concern. The human nose has a 20 part per billion sensitivity for DMDS, versus a sensitivity in the parts per million range for a thiol. I say it is a significant concern because under screwcap, reduction is imminent. Even though the wine smelled clean before bottling, disulfides can rear their ugly head after a year or two under screwcap, making the wine offensive and unpalatable. The younger the wine, the more aggressive the reduction will be. A young red wine bottled under screwcap should raise a large red flag in the winemaker's brain, because it risks harming the potential of the vintage. The goal of bottling is to have the wine come out as good or better than when you put it in there. Modern wine making with screwcaps requires a modern approach.
The first approach I typically see is sulfide remediation. this involves sealing the wine after introducing a strong reducer, ascorbic acid, and letting the disulfide bridges revert back to thiols. This is a slow process, but it will work. After a predetermined amount of time, the winemaker must then treat (after a lab trial!) with copper sulfate. The copper serves as a much stronger bridge between thiols. When it enters the wine, it leaves the sulfate to complex 2 thiols. The resulting complex drops out and is lost either during racking or filtration. If it is not, no worries; the bond will not break. The copper oxidizes the thiols and is referred to as an oxidizing agent. For this reason, we use copper as a preventative treatment under all screwcap. As reduction begins to set in, the copper should 'mop' up any thiols which begin to form. Since the offending chemicals are often in ppb concentrations, and the legal limit of residual copper is 0.5ppm, copper should always be the excess reagent and capable of reacting. This can be a particularly useful technique if the wine is to be bottled a few months after fermentation.
A second technique I have seen is a macro-oxygenation of the wine at bottling. I call it macro because the oxygen is not slowly metered in, we literally ram it in with and air pump and a sparging stone. Once it reaches our desired concentration, estimated by cellar trials, we bottle. The idea is to still have some dissolved oxygen present in the bottle to delay the onset of reduction. I have only seen this done on wines designed to be depleted within 1 year of the bottling date. And I am not completely sold, because it almost always comes with a complimenting increase in the SO2 before bottling to offset the SO2 loss associated with oxygen pickup (and Ascorbic if you used that).
A third solution is slowly developing, and that is screwcaps with designed differences in OTR. If the winemaker knows most of the wine will be drank within 1 year, it is an option for them to select a screwcap with a much greater OTR than cork. This runs a huge risk of turning the bottle to vinegar, but generally those things are worked out with sales and marketing ahead of time.
So the next time you drink wine out of a screwcap and it tastes good, I hope you have more of an appreciation for the work that went into making that wine. I can promise you that the winemaker does.
Wine making can be oversimplified into two facts: the juice must be made into wine, and that wine must be packaged. The wine does not care what bottle it ends up in, or what the label looks like. In creating a good drinkable wine at a lower price point, the packaging choices were obvious. What the wine does care about is the closure in which it resides under. With cheaper packaging comes the decision of cork or screwcap. Before the inception of this brand, I used to scoff at screwcaps. To the inexperienced drinker, it is often a sign of low quality, reductive wines. But with the taming of the screw comes the respect of the screwcapper (in the words of Ferris Bueller, 'if you have the means I'd highly recommend picking one up'). A screwcap is a beast of a different nature, and as we learned more about the closure it taught us much more about the nature of wine in this closure.
Now for some chemistry. Thanks to the rise of the screwcap, we have a plethora of 3 letter acronyms in the bottling room. They mostly refer to the relationship of oxygen and wine, and the efficiency of oxygen in passing by the closure. In a very well known wine movie, there is a scene describing a bottle of wine as a living thing, something that matures and changes with age. This is certainly true, but not all change is good. The 'life' that drives the wine is a complicated and reversible matrix of chemical reactions involving the 'redox,' or reduction/oxidative potential of the wine. I would love to give a gen chem lesson right here, but to keep things simple I will use the acronym that I was taught. OIL RIG - oxidation is loss, reduction is gain. This refers to electron movements between molecules within the wine. To be oxidized is to lose electrons (there is a definied number for each molecule in each oxidation state). Some molecules want electrons more than others, and this difference in affinity gives rise to cascading chemical reaction. That is to say there is a strong interconnection between A and D when A reacts to form B, B reacts to form C, and C reacts to form D. What stops that reaction from reaching equilibrium and hence ceasing to age? OTR, or oxygen transmission rates. Each modern closure lets a predictable amount of oxygen react with the wine during aging ( perhaps this gives rise to bottle shock? oxygen is introduced during bottling and then the wine is closed. it would seem to me a macro-equilibrium would need to take effect, thus explaining the change in taste after bottling).
I could write for days about the reactions of oxygen and wine, but for now I want to concentrate on the reductive qualities associated with a screwcap. The approach to winemaking must consider the closure which the wine will end up under, and the period of time the winemaker has to stabilize the redox state of the wine.
Wines begin their life with a huge desire for oxygen. Yeast have a hunger for oxygen, and if they do not get it poor fermentation and off aromas will develop. After primary fermentation, the wine still needs a substantial amount of oxygen to aid in the aging process (like every rule, there are exceptions to this. and also I am thinking WV pinots here). Anyone who has opened a tank to the smell of deep cooked meat and earth has seen this first hand. An excellent indicator of reduction in the early stages of winemaking is the formation of hydrogen sulfide, H2S. H2S is in a redox equilibrium with SO2 (or O2S of you would prefer). Organic chemistry simplifies redox relationships to say a molecules' oxidation state changes when the number of oxygen bonds change. This is a firsthand example. In a reduced environment, sulfur easily exchanges its oxygen molecules for two hydrogen molecules. Upon introducing excess oxygen, H2S is oxidized from its farty smell back to the wonderfully choking SO2 stench. Cellar operations during harvest use this principle, the winemaker should splash rack in order to provide the necessary oxygen and age the wine. The oxygen consumption potential of a young red wine is huge, oxygen is in high demand and is broken down from atmospheric dioxygen into individual molecules which fit like puzzle pieces in the chemical matrix. As the wine is allowed to use oxygen where it is needed, the consumption potential begins to fall. This is where the winemaker must make educated decisions about the timing of bottling under screwcap (a post for another day...the best time to treat H2S and mercaptans is in a very reductive state, more to come...).
A major concern when bottling under screwcap is the presence of disulfides and mercaptans (thiols). The two are closely related. A mercaptan is the sulfur containing analog of an alcohol. For example, methanol has the formula CH3OH. Methanethiol has the formula CH3SH. Sulfides have a unique property of forming a disulfide bridge. The two sulfur atoms can form a covalent bond and stick together in the formula CH3SSH3C. This will occur in a reductive environment and is of significant concern. The human nose has a 20 part per billion sensitivity for DMDS, versus a sensitivity in the parts per million range for a thiol. I say it is a significant concern because under screwcap, reduction is imminent. Even though the wine smelled clean before bottling, disulfides can rear their ugly head after a year or two under screwcap, making the wine offensive and unpalatable. The younger the wine, the more aggressive the reduction will be. A young red wine bottled under screwcap should raise a large red flag in the winemaker's brain, because it risks harming the potential of the vintage. The goal of bottling is to have the wine come out as good or better than when you put it in there. Modern wine making with screwcaps requires a modern approach.
The first approach I typically see is sulfide remediation. this involves sealing the wine after introducing a strong reducer, ascorbic acid, and letting the disulfide bridges revert back to thiols. This is a slow process, but it will work. After a predetermined amount of time, the winemaker must then treat (after a lab trial!) with copper sulfate. The copper serves as a much stronger bridge between thiols. When it enters the wine, it leaves the sulfate to complex 2 thiols. The resulting complex drops out and is lost either during racking or filtration. If it is not, no worries; the bond will not break. The copper oxidizes the thiols and is referred to as an oxidizing agent. For this reason, we use copper as a preventative treatment under all screwcap. As reduction begins to set in, the copper should 'mop' up any thiols which begin to form. Since the offending chemicals are often in ppb concentrations, and the legal limit of residual copper is 0.5ppm, copper should always be the excess reagent and capable of reacting. This can be a particularly useful technique if the wine is to be bottled a few months after fermentation.
A second technique I have seen is a macro-oxygenation of the wine at bottling. I call it macro because the oxygen is not slowly metered in, we literally ram it in with and air pump and a sparging stone. Once it reaches our desired concentration, estimated by cellar trials, we bottle. The idea is to still have some dissolved oxygen present in the bottle to delay the onset of reduction. I have only seen this done on wines designed to be depleted within 1 year of the bottling date. And I am not completely sold, because it almost always comes with a complimenting increase in the SO2 before bottling to offset the SO2 loss associated with oxygen pickup (and Ascorbic if you used that).
A third solution is slowly developing, and that is screwcaps with designed differences in OTR. If the winemaker knows most of the wine will be drank within 1 year, it is an option for them to select a screwcap with a much greater OTR than cork. This runs a huge risk of turning the bottle to vinegar, but generally those things are worked out with sales and marketing ahead of time.
So the next time you drink wine out of a screwcap and it tastes good, I hope you have more of an appreciation for the work that went into making that wine. I can promise you that the winemaker does.
Better Wine is Coming...
Call this post a mission statement, but this blog is being developed with a specific purpose. While I have the utmost respect for the efforts of winemakers statewide, I don't feel there is a good forum for discussing everything that is scientifically unique about wine making in Oregon. As I continue down my journey in this industry, I am always nagged by questions I would never ask a winemaker. The biggest is one I'm sure every wine drinker has wondered, "Did you mean to do this to the wine??" I do not ask this to offend or to put down anyone, I am just boggled sometimes about whether the obvious flaws that show up in Oregon wines are due to a lack of education, a lack of commitment, or a lack of money and technology (yes I believe they are directly linked). Or are they created intentionally by a minimalist wine making approach?
While I am all for terroir and small, expressive production, I am referring to flaws which are classically pointed out in tasting classes and wine schools across the country. Things like excessive VA, EA, browning, sulfides, excessive redox, tartrates in young vintages, flaws that are immediately apparent to anyone who has the pleasure of working with wine every day. The reason things like this concern me is that we are in a very complimenting industry. The success of all of our wineries (although definitely pioneered by a few) can be attributed, at least in part, to the mystique of Oregon as a wine growing region. I believe that it benefits all of us when one of us does exceptionally. However, the converse is true as well.
It is worth noting now that my background is not traditional to a winemaker. I was not raised on a vineyard, I have always loved science and elected to study Chemistry at a liberal arts college. What led me to enjoy wine making is the overlap between science and nature, I know we cannot possibly predict or control every aspect of wine making. But we can sure try. And it is this philosophy that has led me to write this blog. My goal here is to address and discuss the scientific problems and challenges that confront winemakers in this state on a daily basis. Chemistry can be scary and intimidating to some, but it is the cornerstone of sound wine making. A knowledge of what goes on in wine beyond the surface is invaluable, and in my experience tasting in some parts of the state, often overlooked. All I can do is hope that this blog finds the correct readership and is used as the forum and tool that it is meant to be.
While I am all for terroir and small, expressive production, I am referring to flaws which are classically pointed out in tasting classes and wine schools across the country. Things like excessive VA, EA, browning, sulfides, excessive redox, tartrates in young vintages, flaws that are immediately apparent to anyone who has the pleasure of working with wine every day. The reason things like this concern me is that we are in a very complimenting industry. The success of all of our wineries (although definitely pioneered by a few) can be attributed, at least in part, to the mystique of Oregon as a wine growing region. I believe that it benefits all of us when one of us does exceptionally. However, the converse is true as well.
It is worth noting now that my background is not traditional to a winemaker. I was not raised on a vineyard, I have always loved science and elected to study Chemistry at a liberal arts college. What led me to enjoy wine making is the overlap between science and nature, I know we cannot possibly predict or control every aspect of wine making. But we can sure try. And it is this philosophy that has led me to write this blog. My goal here is to address and discuss the scientific problems and challenges that confront winemakers in this state on a daily basis. Chemistry can be scary and intimidating to some, but it is the cornerstone of sound wine making. A knowledge of what goes on in wine beyond the surface is invaluable, and in my experience tasting in some parts of the state, often overlooked. All I can do is hope that this blog finds the correct readership and is used as the forum and tool that it is meant to be.
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