Can’t we all just get along? Probably not.

Every wine is different, even the same wine will taste different on different days – this is probably the greatest thing about the beverage. With Coca-cola or Budweiser one knows what one is getting; it is the mystery of what will be inside that bottle that makes wine so exciting.

Decades ago not much was known about the chemistry contributing to a wine’s taste and smell, but as science has progressed so has our understanding of the chemistry behind the flavor. With the ability to isolate yeast strains much of the guess work has been taken out of winemaking. Now it’s common practice to add yeast nutrient so the fermentation takes place seamlessly, creating fewer “stinky” aromas. This all sounds great, but with every new technology terroir loses its place as the driving force behind a wine and gives way to lab coats.

Santa Ynez Valley

Recently we discovered what causes cork taint in a wine. It’s the presence of a compound known as trichloroanisole or TCA – when this is present in a wine it is undeniably flawed. Nobody wants to drink acidic basement water, which is in effect what the wine becomes. When a wine’s volatile acidity (VA) is high enough, aromas of vinegar or nail polish remover become prevalent, but elevated levels are pleasant before becoming obnoxious, and personal tastes vary on the amount of acceptable VA.

Other than these two flaws (which I would argue VA only is at extremely high levels), there is nothing else commonly found which causes me to deem a wine as flawed. Oxidation could be mentioned, but some wines are purposely oxidized. Brettanomyces is often considered a flaw in the new world, but the yeast and it’s byproducts are commonplace in some famous old world wines, and honestly, I like a little stink in my wine and there’s nothing wrong with that.

It is varying levels of compounds which were inherent to the grapes and the oak as well as those produced by yeast and bacteria which contribute to the uniqueness of a wine. To me all four of these factors combine to create the elusive terroir – but the trend has gone the way of creating predictable character by eliminating the last two factors. Commercial yeast strains may produce pleasant fruity esters, but an important piece of terroir is lost. Similarly, adding nutrient might help avoid a stinky fermentation, but shouldn’t the wine represent the nitrogen levels that are naturally present in the vineyard? A fermentation with native yeast and low nitrogen levels will likely produce higher levels of compounds such as Dimethyl Sulfide (DMS), which can cause aromas of cooked cabbage, canned corn, and Walla Walla terroir.

This particular compound was a subject of controversy last week when Kori of Wine Peeps wrote on her blog about sending a wine from Cayuse, a well known Walla Walla Valley winery, to ETS labs to test for flaws. She claims the results show that Cayuse is inherently flawed, due to higher than normal levels of DMS (312 micrograms per liter). She also notes that the VA was slightly above sensory threshold and the pH was “high” – although neither number was provided.

Walla Walla Valley

Yes, Cayuse wines do have a high pH, as do many red wines produced in Washington. I supposed this means that Christophe Baron could have dumped in a few kilograms of tartaric acid to compensate for the natural result of growing wine grapes in the Walla Walla Valley. And to prevent high levels of DMS he could have added a commercial yeast strain and nutrients to help along the fermentation.

Had Christophe done this I’m sure the wine would still be good, as his vineyards are nothing short of awesome, but they wouldn’t be the same. Cayuse is one of very few Washington (OK, technically Oregon) wineries creating a unique product that gets me excited. To suggest that these wines are flawed because they are different than his neighbors is exactly what I can’t stand about the current state of the wine industry. The numbers don’t matter – the wines are distinctive and many are among the best I’ve ever tasted. I highly doubt that Christophe is too concerned over this accusation, either. It’s unlikely the seven year waiting list for his wines will suddenly crumble – I know I’m not giving up my spot. Does this mean Christophe could declare, “I fought the flaw and the wine won”? That doesn’t work as well as I had hoped.

When the day comes where all wines are treated as chemistry projects the entire industry should be considered flawed, and I’ll start looking for a new career.

—————–

P.S – thanks to Ben Simons of Vinotology for bringing this issue to my attention, and thanks to Ed Thralls of Wine Tonite! for taking my orphan chair. Not my chair, not my problem, that’s what I say.

Cabernet’s Character Flaw

There are a few things about the world, and the United States in particular, that are hard to understand. Chardonnay is the top selling varietal wine in the country – this isn’t surprising. Its name rolls off the tongue even for an English speaker, and it’s a low acid grape; we like it big, round, smooth, and sometimes buttery. The top red grape in the country is slightly harder to understand and much harder to pronounce.

Drop the Sauvignon in Cabernet Sauvignon and the name is compelling and simple; perhaps this explains its success. It also doesn’t hurt that California seems to do especially well with the grape – I can’t say the same about Merlot (although Washington is another story). Besides the long name, the main reason the fact that the United States’ drinking public has chosen Cabernet Sauvignon as its go-to red bewilders me is its varietal character.

Cabernet Sauvignon hails from France

The classic Cabernet Sauvignon aroma descriptors (at least to me) are mint, eucalyptus, black current, and green bell pepper. I would say this sounds like a great combination, but it seems more and more than any hint of herbaceous or “veggie” character in a wine is called a flaw. We’ve become a fruit-forward society; and this isn’t limited to San Francisco, but it’s all around us. While a wine which smells and tastes like fruit can be delicious, it’s the non-fruit qualities of wine which I find so interesting.

This bell pepper smell is caused by a group of compounds collectively referred to as pyrazines, and it’s not only Cabernet Sauvignon which possesses these. There are plenty of grapes, however, which tend toward the fruity side even when under-ripe (Syrah comes to mind). Pyrazine levels can be lowered by tricks such as early leaf stripping and fermenting in the presence of oak, but maybe instead of manipulating the vine or the wine to strip its varietal character we should be celebrating the presence of one of Cabernet’s defining qualities.

This weekend I propose anyone who reads this to find a Cabernet Sauvignon and seek out the bell pepper. Once it hits the nostrils one must bask in its glory. Alternatively, anyone in Sonoma County is welcome to stop by my apartment and try the 1987 Domaine Michel Cabernet Sauvignon, which I picked up a case of for $40 a few nights ago. Mint, bell pepper, and bliss. It doesn’t hurt that it’s my birth year, either.

Wild Fermentation

All this talk about wild fermentation has really got me excited.  Here’s more about how yeast and bacteria turn grapes into wine.

The following thoughts are based on a conversation I had with Mike Moyer, Professor of Enology at the Walla Walla Community College, while taking my laboratory practical exam.

Wild fermentation with red wine is a great idea.  When a harvest comes in off the vines, there are dozens of species of yeasts, and even more bacteria that are living on the skins.  When we crush and destem the grapes, we introduce a lot of oxygen into the must (crushed up grapes), and this is primetime for microbes to start eating and reproducing.

The first species of yeasts to start eating and making more of themselves include names like Kluyveromyces, Candida, Hansenula, Kloeckera, Dekkera,  and Torulaspora.  Some of these are really good at making chemicals like nail polish remover (ethyl acetate), while others create funky, rubbery, tar, complexities that make a wine multi-dimensional and interesting, if not incredible.  Most of these species die when the wine approaches 3-7 percent alcohol, and then Saccharomyces takes over and eats all the sugar.  He’s the best at this.

Ahhh…I just poured a glass of 2008 Lemberger, and am really happy that I did.  Ok, back to fermenting.  Reds.  Wild.  Great idea if you are looking for multi-dimensional, borderline funkdified, traditional styles.

If you want  clean-cut, American/New World, polished, buffed styles of wine, then your producer has probably selected a packaged yeast.

White wine?  Different story.  Chardonnay?  Yeah, ok.  You can make a wild ferment Chardonnay, because…drum roll…malo-lactic conversion is acceptable.  This is the bacterial conversion of malic acid into lactic acid.  This process make a wine less tart while changing the aromatic profile from apples and fruit towards buttery and nuts.

Riesling? Chenin Blanc? Sauvignon Blanc?  Gewurztraminer?  Wild fermentation is more likely to promote the malolactic bacteria, and these wines will turn out too flabby for what most white wine consumers would prefer.

Both Professor Moyer and myself agreed that if we had a time-machine, we would definitely use it to go back about two hundred years and see how European aromatic white wine regions made their wine.

Here are the techniques modern white wine producers employ to prevent the ML conversion:

1)Refrigeration 2)Sulfites 3)Lysozyme (naturally present in tears, saliva, and egg whites) 4)Low pH 5)Sterile filtration 6)Velcorin

Of these, the one that would be best readily available to Loire, Alsatian, Austrian, Swiss, and Northern Italians of the Middle Ages, up through the High Renaissance until the Industrial Revolution would be 4) low pH.  Our bet is that pre-modern producers picked earlier to achieve these crisp, tart, and aromatic styles that are sought after for the glory and happiness that they bring.

To conclude, if you are looking to try a wild fermented, gutsy, steely, earthy Chenin Blanc, then bring a Coulee de Serrant over to our house and you can be a featured guest on the terroirist show.

Alternatively, try an Old World Winery Sonoma/Mendocino Sauvignon Blanc.  Complex, creamy, soy character with passionfruit, maybe the scent of the road after a short early summer downpour.  Yum…. this wine went excellently with our dinner of hot dogs on ciabatta bread.

Your Friend,

Michael the Microbiologist

Michael Penn

Aromatics: An evolutionary perspective

Welcome again to Terroir Tuesday.   I hope all haven’t been waiting too long to learn more about really cool stuff.  Tonights essay summarizes a recent talk given at the WAWGG Conference in Richland, WA by Assistant Professor Gavin Sacks of Cornell Univeristy entitled “Riesling Aroma Precursors.”

I hope you’ve selected at least a three to four year-old riesling to accompany you in tonight’s reading.  A gewurztraminer, gruner veltliner, or a siegerrebe would also be good choices.    Maybe some risotto to help wash it down.  Yum.  I don’t intend tonight’s read to be too complex, but rather full of intrigue, elucidating facts, and brilliant inspiration to carry you into tomorrow.  Wednesday. 

Ok, I start with a question:

Q: Why do grapes and wine have aroma?

A: To coax their seed dispersal assistants to eat them of course.

Nice.  Good answer.  So next question,

Q: Just who are these seed dispersal assistants?

A:  Hmmm…not sure.  Why don’t you tell me?  You’re the one writing this stupid essay.

Q: Alright, if that’s the way its got to be.  For anyone who has ever planted a vineyard, and then attempted to harvest grapes from said vineyard, you may have noticed that the birds ate the grapes.  Many of them.  Maybe all of them.  This is why grapes have aroma compounds.  To attract birds to eat the grapes, and then poop the seeds somewhere else.  This is why grape seeds are small, grapes are perfumed, but not overpowering, and they are often red.  Fruit that is designed for birds have small seeds, thin skins, go through dramatic color change as they approach ripeness, and produce sugar.

Fruit that is designed for mammals on the other hand is quite different.  The fruit is bigger and fleshier.  This is why passionfruit, guavas, avocados, durians, and other savory, fleshy, big pitted fruits are designed.  Birds like dainty scents, mammals like stinky scents.

If you learn anything about wine aromatics tonight, learn this.  A grape has many aromatic compounds, but a vast number more are stored inside the vacuoles of the grape and are termed “aromatic precursor molecules.”  They are often chemically bonded to either a sugar molecule, or a sulfur-containing amino acid.

In that form, they do not add aroma or flavor to the grape or juice.  Through the process of primary fermentation, the eating of sugar by yeast, and further through the process of wine aging, these precursor molecules, attached to either sugar or amino acids, are unlocked and the aroma compound travels up the glass, and into your nose.

Huh?  Really?  Does that mean…it can’t be…Yes, go ahead.  Ask it.

Q: Why do grapes have “aroma precursor” molecules since birds don’t make wine?

A: God wants us to enjoy wine.  (Gasps, shrill horror sounds)

Q: Are you about to get religious on us?

A: No.  I’m just saying that it’s wierd that grapes have aroma compounds that are only unlocked through the winemaking process.  Here’s a little more.  Gavin and his research team looked at the aroma precursor molecules in Riesling, in particular monoterpenes and the infamous, TDN.  I won’t bother to tell you what TDN stands for, but it smells like kerosene or diesel, and it is almost exclusively found in aged rieslings, more often Alsatian or German ones than in New World wines.

Here’s some crazy stuff they found out.  They did a petiolar (leaf stem) analysis, and found that when the vine was damaged by plucking a leaf off or cutting the shoot off at the tip, the sap that flowed to the scars contained higher levels of terpene (the beautiful floral scents).  In other members of the plant world, these chemicals are in fact toxic to some animals, and are used to protect the plant from being eaten, or infected by disease.   As the wound heals, the vine now has these toxic chemicals to dispose of.  To protect itself from their toxicity, it attaches a sugar or an amino acid to them, and stores them in the grape.

Q: Hmmm…does that mean muscat is poisonous?

A: No.  It just smells really good.  We are ingesting teensy amounts of these aroma compounds.

Q:Cool.  Is that it?

A: Almost.  TDN is not in the terpene family, but in a family of chemicals called the norisoprenoids.  I love that word.  Say it again with me, norisoprenoid.  The TDN precursor comes from a molecule that is involved in photosynthesis.  Gavin’s team found that if they pull leaves right before veraison, (in July when the berries are changing color), the wines will have maximum values of TDN.  The hypothesis is this,  in response to the increased sunlight on the vine and the loss of leaves, the vine compensates by making more photosynthesis (turning sunlight into sugar) molecules to deal with the damaging effects of the sun.

As the vine and the fruit mature into harvest, those extra molecules are then stored in the vacuoles (storage units of a cell) of the grapes.  When we make wine, yeast unlocks the sugar bond, aging continues to unlock them, and voila, a delicate balance of rubber, diesel, apples, and roses.  Here’s a toast to riesling producers, from Washington State, to New York, from Colmar,  to Geisenheim.

Okay, let’s end on something really cool.  Vitis labrusca, the grapevine that gives us such wine as Manischewitz and other Concord wines, contains a chemical called methyl anthranilate.  Sounds really good, huh? It’s not.  It’s what gives concord wine that unmistakeable flavor of…weasel urine.  You think I just made that up huh?  It turns out one of the only other places in nature that this chemical is found is in the scent ducts of weasels.

Q: Wierd.  Why would I want to drink weasel urine?

A: Exactly.  You and the birds that might steal the concord grapes will be thoroughly displeased.  Explanation: The grape makes this chemical to let the birds know that a weasel is awaiting in the canopy ready to pounce.  Concord grapes tend to be fleshier, have bigger seeds, and yes, are naturally dispersed by mammals.

Cheers

Michael Penn

Those Pesky Sulfites

Almost all wines have a “contains sulfites” notice (exception is organic wines — which are quite rare), but what exactly are sulfites and why are they added to wine? They’re often wrongly blamed for “red wine headaches”, the cause of which is still debated. In truth, white wines generally have a higher concentration of sulfites than reds. Sulfur dioxide (SO2) is not all bad; it’s one of the reasons wine can age so well, and to make wine without it is a very difficult task.

Sulfites perform three functions in wine: first, they prevent the growth of microbes. Secondly, they protect the wine against oxygen, and thirdly, they bind to unpleasant aroma compounds such as acetaldehyde. The latter two of these functions are related through complex chemical reactions which I won’t go into, therefore encouraging continued reading of this article.

Sulfites are typically first added to the wine right at the crusher. This protects the juice from oxidation and it prevents any bacteria from living in the must. Almost all of this dimishes by the end of fermentation. For reds the wine is typically inoculated with bacteria after alcoholic fermentation to undergo the malolactic fermentation, which, among other things, provides the wine with microbial stability and a rounder mouthfeel. Sulfites are then added every few months after malolactic fermentation is complete while the wine is maturing in barrel to help protect it.

Whites which don’t go through malolactic fermentation require a closer monitoring of sulfur levels to ensure bacteria can’t build up a population. Whites are much less stable for this reason, and off-dry whites such as many Rieslings are even less so, therefore making sulfur dioxide a critical wine making tool. White wines also don’t have the anti-oxidants that red wines have to help protect them from oxygen (thus the common belief that red wine is healthier, which is probably true). Next time you drink a wine and notice that “contains sulfites” warning, take comfort in knowing that it has aided in making the beverage enjoyable, and they won’t give you a headache.