Everybody in the (Pyrazine) Pool!

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Most wine students have heard of pyrazine—methoxypyrazine to be exact—as the chemical partially responsible for the “freshly cut green grass” aroma found in Sauvignon Blanc, as well as a range of other herbaceous aromas—from green bell pepper to gooseberries to asparagus—found in various wines including Cabernet Sauvignon, Cabernet Franc, and Carmenère.

Pyrazines are legendary. The legend has been repeated countless times, and it goes something like this: “The scent of pyrazine is so strong; it can be detected at concentrations equal to five drops in an Olympic-sized swimming pool.”

I’ve heard this so many times, I decided to check it out. After all, so many oft-repeated facts about wine turn out to be just oft-repeated myths, as I am sure you know!

For starters, according to Jancis Robinson, et al in The Oxford Companion to Wine (third edition), the sensory threshold for the strongest form of methoxyprazine is 215 ng/L in white wine. The ng refers to nanograms, which equate to one billionth of a gram.

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As it turns out, after a bit of rudimentary calculations,* the sensory threshold for pyrazines is not exactly five drops in an Olympic sized swimming pool, it is closer to 11 drops—still a legendary amount.

Which leads us back to where we started: this stuff is sturdy.

In reality, what we refer to as pyrazines in wine are technically nitrogen-containing (organic) aroma compounds produced as a secondary by-product of amino acid metabolism. There are three main types, as applies to wine: Isobutyl-methoxypyrazine (IBMP), Secbutyl-methoxypyrazine (SBMP), and Isopropyl- methoxypyrazine (IPMP). IPMP appears to be the most abundant of the three, and is most-often implicated in the “asparagus” range of aromas. IBMP—which accounts for the 215 ng/L threshold— appears to be the strongest and is often detected as green bell pepper or gooseberry aromas.

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Pyrazines are, for the most part, created in the vineyard. They are initially produced during the early stage of fruit set as a defense/survival mechanism for the baby grapes (a mouthful of raw herb flavor is perhaps none too delectable to baby goats and wild boars). The level of pyrazines in the grapes can run amuck in cases of excess water or overly-dense canopies—particularly if the baby grapes spend too much time in the shade.

I happen to love herbaceous character in my wines, so as far as I am concerned, “bring on the pyrazines”! However, most wine lovers prefer their wines to be balanced, as opposed to the green-meanie style of wine that I adore.

Luckily, Mother Nature has her own ways of controlling pyrazines. For one, the level of pyrazine in grape berries typically drops as grapes approach ripeness. For another, increased sun exposure will sort of “burn them off.” On the other hand, cloudy days, cool climates, dense canopies, over-watering, and less-than-ripe grapes are a pyrazine’s best friend.

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Everybody in the (pyrazine) pool!

.*If we do the math—which in this case is admittedly non-scientific and making use of generalizations such as standardized water volume vs. weight—it might go as such:

  • For starters, there are 2,500,000 liters (2.5 mega-liters [2.5 million liters]) of water in an Olympic size swimming pool.
  • If we multiply 215 nanograms times 2.5 million, we see that 215 X 2,500,000 = 537,500,000 nanograms, or 0.537 grams.
  • If one teaspoon of water equals 4.93 grams, then 0.537 grams = 0.11 of a teaspoon.
  • If we use a typical culinary calculation of 98 drops in a teaspoon, 0.11 of a teaspoon = 10.78 drops.
  • Conclusion: It’s not exactly five drops in an Olympic sized swimming pool, but at just shy of 11 drops, it is still a legendary amount.

References/for more information:

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

Zip and Zest: Five Fast Facts about Tartaric Acid (and Wine)

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Is it weird that tartaric acid has been on my mind a lot lately? I suppose dreams of tartaric acid are not so unusual for those inclined to the study of wine, and a little bit of a treatise on tartaric might be just the ticket to soothe my soul. So here goes, five fast facts about tartaric acid!

#1: When it comes to tartaric acid, grapes rule: Tartaric acid is one of the main natural acids found in grapes and —interestingly enough—grapes have a higher concentration of tartaric acid than any other fruit or vegetable. Besides grapes, measurable quantities of tartaric acid can be found in avocadoes, bananas, cherries, and grapefruit. However…for the record, most fruits and vegetables—including blackberries, blueberries, apples, apricots, peaches, pears, pineapples, plums, lemons, limes, oranges, and tomatoes—are high in malic acid and citric acid, but contain very little (if any) tartaric acid.

#2: Tartaric acid is tongue-tingling and truly tart: Tartaric acid is typically the strongest acid in both grapes and wine, as measured by pH and volume. Tartaric acid typically accounts for one-half to two-thirds of the acid content of ripe grapes. As such, tartaric acid is one of the most important fixed (non-volatile) acids in wine, along with malic acid.

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#3: Tartaric acid is strong and stable, part one: Tartaric acid is often used as an additive in winemaking (for good reason): In addition to the obvious impact on taste and flavor, proper levels of tartaric acid are important to the microbial stability of a wine. Tartaric acid resists decomposition and microbial attack, and is therefore often used as an additive  when acidification is needed. Malic acid, on the other hand, is easily broken down by malolactic fermentation or other processes. For these reasons and more, tartaric acid is the substance most often used when acidification is needed in the winemaking process.

#4: Tartaric acid is strong and stable, part two: Tartaric acid typically is contained in wine grapes at a concentration between 2.5 to 5 g/L at harvest, and it remains relatively stable throughout the ripening process. Conversely, wine grapes often contain more than 20 g/L of malic acid prior to veraison—however, a good deal of this is used for energy during respiration. Levels of malic acid at harvest are typically closer to 1 to 4 g/L. Tartaric acid is also metabolized during respiration, but at much lower levels than malic acid.

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#5: Tartaric acid is related to, but not (quite) the same thing as cream of tartar: Students of wine are sure to be familiar with the propensity of tartaric acid to form wine diamonds (particles that separate from the wine and look like tiny crystals of rock salt). Wine diamonds can form in the tank, during barrel aging, or in the bottle—particularly if the wine is subjected to cold temperatures. Tartrates can be prevented in the bottle via pre-bottling cold stabilization. Tartrate crystals scraped from the interior of oak barrels once inhabited by high-acid wines can be used to produce cream of tartar—a white powder that is often used as a stabilizing or leavening agent in cooking (particularly with egg whites, sugar work, or baking). Cream of tartar is basically partially-neutralized tartaric acid, produced by combining tartaric acid with potassium hydroxide. Cream of tartar, when used in baking, helps to activate baking soda, which is alkaline. As a matter of fact, cream of tartar combined with baking soda is the formula for baking powder.

References/for more information:

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

I’ve been Shattered

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As a good student of wine, I can tell you what shatter, aka coulure is. I can even quote (probably verbatim) the information on it from the CSW Study Guide—here goes!

“A malady known as coulure (“shatter” in English) can cause poor fruit set, with many flowers failing to become fully developed berries.”

Yep. That’s it—and that was about the extent of my knowledge until one night when I suddenly wanted to know more. So, a few textbooks, websites, and phone calls later, here is what I now know about coulure.

For starters, the word is pronounced “coo-LYUR.”

Put simply, coulure occurs when a large number of a vine’s grape blossoms stay closed, or for some other reason they fail to become fertilized. These failed flowers never get the chance to develop into grape berries but rather shrivel and fall off the vine.

In French, weather-induced coulure is referred to as coulure climatique, and the main culprit behind coulure is indeed the weather.

  • The uncooperative weather—when too cold, rainy, or wet (shatter is a bigger threat in areas with marginal climates)—slows down the plant’s rate of photosynthesis, which leads to carbohydrate deficiencies in the vine. This deficiency causes the vine to conserve its resources, and the energy that would go into ripening flowers and fruit is diverted elsewhere. The blossoms eventually shrivel and drop off, along with the small stems that attached the blossoms to the vine.
  • Excessively high temperatures during flowering and fruit set can cause coulure—again as a result of the shut down of photosynthesis—as the necessary enzymes lose their shape and functionality. In a prolonged heat event, coulure may be caused via excessive shoot-and-leaf growth as well as cellular respiration, either of which can lead to carbohydrate deficiencies.

Photo by Hvczech (Public Domain/via Wikimedia Commons)

Besides the weather, coulure can be caused by overly-fertile vineyard soils and excessive use of high-nitrogen fertilizers, both of which can lead to excessively vigorous vine growth that can drain a plant’s carbohydrate reserves. Another possible cause is overly vigorous pruning, which can fail to provide enough potential for the growth of amount of leaf grown necessary for photosynthesis. In addition, certain grapes, such as Grenache, Malbec, Merlot, and Muscat Ottonel are particularly prone to coulure.

Coulure is not always preventable, but some good practices to follow include:

  • Taking care not to over-prune and encouraging the vines to develop enough leaf coverage to provide for adequate photosynthesis.
  • Tip-trimming (snipping the tips of developing shoots) near the end of the flowering period can help prevent carbohydrate deficiencies.
  • In some places, performing winter pruning late in the season may reduce the risk of coulure by delaying bud break which in turn increases the probably for warmer weather at flowering.

Hopefully, all this chitter-chatter has cleared up a bit about shatter (sha ooobie shatter)!

References/for more information:

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

Wine Geo: Pass, Gap, and Gorge

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I checked the ever-expanding list of American Viticultural Areas (AVAs) the other day, and for some reason my attention was drawn (once again) to the various geological formations that are mentioned in the titles. These include ridge, slope, plateau, sound, highlands, peak, ledge, and delta.  Fascinating! But…what do they all mean?

Let’s consider these for now: pass, gap, and gorge—as in Pacheco Pass, Templeton Gap, and Columbia Gorge.

What is a pass? Geomorphologically speaking, a pass (often referred to as a mountain pass) is a low-lying, somewhat flat area surrounded by much higher and more rugged terrain. A pass forms when a glacier or stream erodes away between two mountains or a series of mountains. Passes are typically the easiest route for people to travel across mountain ranges and many of the best-known passes in the world—such as the Great St. Bernard Pass in Switzerland and the Khyber Pass between Afghanistan and Pakistan—have served this purpose for millennia.

The Pacheco Pass AVA is located in north/central California, straddling the borders of San Benito and Santa Clara counties.  Casa de Fruta, part of a large fruit orchard and fruit stand complex catering to thirsty tourists on the road to Gilroy and Santa Cruz, is the only winery within the AVA. The area was awarded an AVA in 1984 after a petition was filed by the Zanger family (the owners of Casa de Fruta), who produce fruit wine under the Casa de Fruta label and vinifera-based wines under the Zanger Vineyards label.

Highway 152 along the Pacheco Pass. Photo by Chevy111 via Wikimedia Commons

The Pacheco Pass itself is a 15-mile long corridor that crosses the Diablo Range (part of the California Coast Mountain Ranges) along what is now State Highway 52. The Pass was named for Francisco Perez Pacheco who owned the land in the mid-1800s, back when the area was still a part of Mexico known as Alta California. For a time in the 1880s, the pass was known as Robber’s Pass due to two highwaymen that robbed (and sometimes murdered) travelers along the route. Even today, the stretch of the Highway 152 from Los Banos to Gilroy is quite dangerous, as witnessed by the high number of traffic accidents. There are even rumors that the pass is haunted (best not to pick up any hitch-hikers).

What is a gap? A gap is also a low area between two mountains; however, gaps are smaller than passes, and therefore more rugged and difficult to navigate.  Gaps (sometimes referred to as water gaps) are often created through the twin forces of water erosion and tectonic plate uplift.

A wind gap is a former water gap that no longer has any water due to stream capture (the diversion of a stream from its bed into a neighboring stream). The narrow valleys that remain behind after the stream has diverted allow rain, fog, and other climate features to penetrate beyond the point where the mountains would typically halt their progress.

The Templeton Gap District AVA is one of the 11 sub-appellations of Paso Robles. Surrounding the town on Templeton, it is one of the four sub-appellations hugging the western edge of the Paso Robles AVA and is the coolest of them all. The area benefits from a series of water and wind gaps carved through the California Coast Mountain Ranges by some long-forgotten water ways in addition to the Paso Robles Creek and the Salinas River. These gaps draw cool, moist air from the Pacific Ocean inland towards Paso Robles.

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What is a gorge? A gorge is deeper than a pass or a gap, and is better described as a narrow valley with steep, rocky walls and an often-tumultuous river running through the bottom. The term comes from the French word gorge, which means throat or neck.

Wine students will easily recognize the name of the Columbia Gorge AVA, which straddles the borders of Washington State and Oregon.  The gorge itself is a deep canyon—up to 4,000 feet deep—of the Columbia River that stretches on for over 80 twisty, turn-y miles following the river as it flows west through the Cascade Mountains.  (The AVA covers about 40 of those 80 miles.) The Columbia Gorge (also technically a “water gap”) is the only water route from the Columbia River Plateau to the Pacific Ocean, and was used in 1806 by the Lewis and Clark Expedition (the first U.S. Army expedition to cross what is now the western portion of the United States) to reach the Pacific Coast.

The Columbia Gorge AVA is known for having a remarkable diversity of specific microclimates within its relatively small boundaries—so much so that the Columbia Gorge Winegrowers invite you to experience their “world of wine in 40 miles.” The soils of the Columbia Gorge AVA include alluvial soils from the river beds, colluvial soils from landslides, and soils from volcanic activity (hello, Mount Hood and Mount Adams). The elevation of the vineyards ranges from just above sea level to 2,000 feet high. The cool, moist air coming from the west turns warmer and drier as it travels inland, even losing an inch of rain a mile from west to east. That’s what we call diversity.

The Columbia Gorge

Geo notes: In addition to pass, gap, and gorge, other terms may be used to describe the breaks in mountain ridges: notch, saddle, and col, for example. These terms are not too sharply defined; overlaps exist, and usage may vary from place to place. No one ever said wine (or geology) was easy!

Geomorphology is the study of the origin and evolution of physical features of the surface of the earth (and other planets if you care to venture forth).

References/for more information:

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

Chasing Chasselas

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All of the grape varieties in France are chasing Chasselas—or ahead of Chasselas, or running side-by-side with Chasselas.

And you thought Chasselas was just an insignificant little grape that only Switzerland cares about. Think again.

Late last night while I was studying the Bordeaux Wine Guide published by the CIVB (Counseil Interprofessional du Vin de Bordeaux) I saw it right there on page 43: “In France the main families of grapes are defined (by typical time of ripening) according to the usual maturity date of Chasselas (the reference variety).”

I had to read it twice and call four of my wine friends to see if they had ever heard of Chasselas being France’s reference variety. No one had. As such, I did a bit of research.

The quick version is: it’s true.

Back in the 1800s, a French ampelographer named Victor Pulliat (1827-1896) created a classification of grape varieties—The Pulliat Classification—based on their typical ripening date in relation to the Chasselas Doré grape variety

The Pulliat Classification breaks down as follows:

  • Early-ripening grape varieties:  Ripen from eight to ten days ahead of Chasselas Doré
  • First-period grape varieties: Ripen at about the same time as Chasselas Doré
  • Second-period grape varieties: Ripen from 12 to 15 days after Chasselas Doré
  • Third-period grape varieties: Ripen from 16 to 30 days after Chasselas Doré
  • Late-ripening grapes: Typically ripen more than 31 days after Chasselas Doré

Chasselas grapes on day zero (?)

The Pulliat Classification seems like an interesting bit of history in the world of wine, but as I just learned, it is still used. These days, however, the Winkler Scale created by Maynard Amerine and A. J. Winkler of UC Davis—which measures ripening in terms of degree-days or heat summation—is in wider use. The Winkler Scale was designed in 1944 to be used in California but has since been used in many wine growing regions all over the world.

References/for further information:

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

Fuzzy Wuzzy was a Vine

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One of the first things that a serious wine student will learn about Priorat is that it is one of the two DOCa regions in Spain, and that (its red version) is a hearty wine based around the Garnacha Tinta and Mazuelo (Carignan/Cariñena) grape varieties. Next, one might note the list of accessory varieties, which include some well-known international varieties (including Cabernet Franc, Cabernet Sauvignon, Pinot Noir, Syrah, and Tempranillo) as well as a grape known as Garnacha Peluda.

There it is: Garnacha Peluda; otherwise known as Hairy Grenache. The name peluda seems to come from the French pelut and means furry.  How cute is that? The “hairy” part of the name refers to the small white hairs covering the underside of the leaf. Other terms used to describe this hirsutulous (botanical term for slightly hairy) characteristic include downy, wooly, fluffy, fleecy, and fuzzy. But they all mean the same thing: this leaf is hairy.

Garnacha Peluda, a mutation of Garnacha Tinta (aka Grenache Noir), is considered a unique variety and is often referred to as a downy-leafed variant of Grenache—which may make the inquiring mind wonder why a certain grapevine would mutate into such a form. The answer is that growing furry leaves is a biological adaptation. Biological adaptations are changes—structural (either morphological [able to be observed] or anatomical [internal]), physiological, or behavioral—that occur over many generations of plant or animal life in order to make the organism better suited to its environment and to improve its chances of survival.

Garnacha Pelut vineyards in Priorat

Garnacha Peluda vineyards in Priorat

The hairy-leafed variation of Grenache is a result of a morphological adaptation to hot, dry environments such as found in Priorat, as well as the Roussillon and Languedoc areas of southern France. (Note: in southern France, the grape is often called Lledoner [or Lladoner] Pelut.) The fuzzy layer protects the vine from water loss due to transpiration, helps shade the leaves, and reflects sunlight to help keep the plant cool. The hairy-leaf solution is one of several ways plants adapt to hot, dry environments. Others include small leaves, curled-up leaves, wax-coated leaves, woodsy stems, and green stems but no leaves.

Compared to its non-hairy cousin, Garnacha Peluda tends to produce wines that are lower in alcohol, lighter in color, and higher in acidity. The Garnacha Peluda grape is authorized for use in the following wines:

  • Recommended/Principle variety in: Terra Alta DO, Languedoc AOC (as Lledoner Pelut)
  • Accessory grape variety in: Empordà DO, Priorat DOCa, Terrasses du Larzac AOC (as Lledoner Pelut), Côtes du Roussillon and Côtes du Roussillon-Villages AOCs (also as Lledoner Pelut)

Vitis aestivalis varieties and native North American grapes native to the southwest, such as Mustang and Muscadine, are also likely to demonstrate the hairy-leafed adaptation. Many other plants have adopted this downy-leafed adaptation as well, including rosemary, sagebrush, oleander, buckthorn, magnolia, sycamore, potato, petunia, and lamb’s-ear.

Fuzzy-leafed lamb's ears

Fuzzy-leafed lamb’s ears

Another famous hairy-leafed vinifera grape is Pinot Meunier. As meunier means “miller” in French, the grape is so-named for the layer of white, downy hairs on the underside of the leaves, said to resemble grains of flour (as produced by the town miller at the local flour mill). But as we now know, it is all about that morphological plant adaptation.

References/for further information

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net

The pH of it all

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When we talk about wine, we talk about acidity, and when describing wines, one of the typical ways to describe acidity in wine is to use the pH scale. Dedicated students of wine can easily quote 2.9 to 3.9 as the typical range of pH in wine.

I personally love the zip and zest of highly acidic wines and adore Mosel Riesling (the drier the better), New Zealand Sauvignon Blanc, and even 100% Sicilian Grillo. I’ll take the tongue-curling antics of a wine with a pH of 2.9 any day.

But what exactly is pH? You probably already know that it is a scale runs from 0 to 14 and measures how acidic or basic a substance is. But what does that mean? To answer this question we need to dive into some science…we can start with chemistry and biology, and might just have to visit the physics department (and if we are going there, it better be worth it). So here we go!

About the p and the H: First things first—the term “pH” stands for “power of hydrogen.” The term was invented in 1909 by the Danish biochemist Søren Peter Lauritz Sørensen, so originally the “p” stood for potenz (the German word for power). The “H” (for us absolute beginners) is the element symbol for hydrogen, and the pH scale reflects the concentration and type of the hydrogen-based atoms in a solution. (Note: some references define the “p” in pH as “parts” or “potential.”)

What’s hydrogen got to do with it: Hydrogen is the common element to all acids. What determines whether a solution is acidic or basic is the form and degree of saturation of hydrogen ions.

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Define ions, please: To put it as simply as possible—ions are atoms or molecules that have lost or gained an electron over the course of their travels. In the case of hydrogen, this can occur when water splits apart.  If a hydrogen atom loses an electron, it becomes positively charged and is known as a hydrogen ion (H+). If a hydrogen atom gains an electron, it becomes negatively charged and is known as a hydroxide ion (OH).

Hydrogen ions: An acid is a molecule that can split apart in water and release hydrogen ions (thus, acidic solutions have measurable concentrations of hydrogen atoms). Bases are stronger in hydroxide ions. In neutral solutions, the two are roughly equal and they cancel each other out (neutralize each other).  The way that these hydrogen molecules react in water is the basis for the pH scale.

Deliver me from logarithms: The pH scale is logarithmic. Logarithms are multiples of ten; that means that for every full integer on the pH scale, the strength of the acid or base increases tenfold. Thus a pH of 2 is ten times more acidic than a pH of 3—and a pH of 2 is 100 times more acidic than a pH of 4. If this seems confusing, consider another logarithmic scale, the Richter Scale, where an earthquake measuring 7 is ten times stronger than a 6.

Liquid required: A substance has to be water-based in order to have a pH. Powders and oils (such as vegetable oil or olive oil) cannot be measured on the pH scale. There are, however, several other ways of measuring acidity.

The neutrality zone: A 7 on the pH scale is neither acidic nor basic, and considered neutral. Distilled water is generally neutral, but other types of water are not. An interesting (kind of gross) fact is that  human blood is very close to neutral (just slightly basic) and often has a pH of 7.35 to 7.45. Any deviation from this ideal blood pH can have devastating effects on one’s health.

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Just the basics: In the wine world we deal with levels of acidity, but it is interesting to understand the types of substances on the other end of the scale.  Here are a few common items and their basic pH levels:

  • 8: Baking soda, sea water
  • 9: Toothpaste
  • 10: Milk of Magnesia
  • 11: Ammonia
  • 12: Soapy water
  • 13: Oven cleaner
  • 14: Drain cleaner

The equation for pH: Never mind. If you are interested (and have a logarithmic calculator and know how to use it) click here.

References/for more information:

The Bubbly Professor (who has not formally studied chemistry or physics since college) is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net