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—sometimes noted in various wines including Cabernet Sauvignon, Cabernet Franc, and Carmenère.

Pyrazines are legendary. The narrative—which has been repeated countless times—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:

• Robinson, Jancis and Julia Harding: The Oxford Companion to Wine, 4th Edition. Oxford, 2015: The Oxford University Press.
• https://www.winesandvines.com/features/article/68769/How-Viticultural-Factors-Affect-Methoxypyrazines
• https://www.practicalwinery.com/marapr06p13.htm
• http://wineserver.ucdavis.edu/pdf/attachment/102.%20pyrazine%20levels%20in%20several%20varieties%20.pdf
• https://www.sfchronicle.com/food/article/Napa-Valley-Cabernet-s-bell-pepper-controversy-6584908.php

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