Thursday, November 14, 2013

2012 Mohua Sauvignon Blanc – Marlborough, New Zealand




In a previous post I reviewed three Sauvignon Blancs that I tasted in a Study Group that were from distinctly different locations - California, New Zealand and Sancere. In that review I described the similarities and differences of their profiles that are typical of their terroir. But, I didn’t go into detail about the different appellations that make these Sauvignon Blancs so unique and their wines so recognizable.



On Day 6 of the ICC’s Intensive Sommelier Training program we tasted 7 wines; the third was a 2012 Mohua Sauvignon Blanc which was from Marlborough, New Zealand. This wine is very similar to the 2012 Kim Crawford Sauvignon Blanc from Marlborough, New Zealand that I tasted in the Study Group. But what is it that gives Sauvignon Blanc its unique profile and makes those from New Zealand distinct from those of California and Sancere?


It is Pyrazine That Makes The Wine Smell Green!



Sauvignon Blanc has a very distinctive grape fruit aroma that sets it apart from all other white wines. Even if the Sauvignon Blanc is from a warmer region that causes it to display more stone fruit (peach, nectarine, apricot) or tropical characteristics (mango, kiwi, passion fruit), the grapefruit is almost always in the wine. A second and very common attribute in Sauvignon Blanc is a green vegetal characteristic (often described as being like jalapeno, bell pepper, herbs, or grass) that is more prevalent if it is from a cooler climate. The bell pepper aroma and flavor can also be found in red wines such as Cabernet Sauvignon and Cab Franc, especially if they are from a cooler region or cooler vintage. So, what is it that gives these wines that distinctive green characteristic?



It is pyrazine!



Pyrazine is a natural component of many fruits and vegetables and there are three different types:



Isobutylmethoxpyrazine
Isopropylmethoxpyrazine
Sec-butylmethoxpyrazine

The first is more prevalent in fresh bell pepper; the second in green asparagus or peas, and the third in beets. Methoxypyrazines are found in grapes and contribute largely to the herbaceous and bell pepper characteristics. All pyrazines have very low sensory detection thresholds (one to 2 ng/L in white wines and 10 – 15 ng/L in red wines ). Consequently a single grape with pyrazines in 500,000 metric tons of grapes can change the smell of the entire batch and have a significant aromatic and flavor impact on a wine.




While pyrazine may be desirable in Sauvignon Blanc, in red wines it can undermine the black and red fruit characteristics of a wine if it is excessive. Merlot, Cabernet Sauvignon, and Cabernet Franc in cool vintages and regions can contain high enough amounts of pyrazine to make the wine seem as if the grapes were under ripe when harvested and consequently denote a lesser-quality wine.



To counteract this herbal quality in Sauvignon Blanc some wineries will add a small amount of Semillon and/or Muscadelle.  With red wines, greater hang time is allowed for the grapes or other red varieties are often blended in to counterbalance the green notes in the wine.



The Climate and Soils of Marlborough, New Zealand




Now we know that it is pyrazine that makes a wine smell green, why is New Zealand Sauvignon Blanc are so intensely green? The distinctiveness of Marlborough Sauvignon Blanc is due to its unique terroir. Marlborough is located on the east coast of the South Island with mountains to the west, and it is one of the country’s sunniest and driest areas.  In these sunny but relatively ‘cool’ climate conditions, the grapes experience a long slow ripening period.  The average daily temperature during summer is nearly 75 °F (24 °C) but clear cool nights keep acid levels high in the grapes. These cool temperatures with cool/warm diurnal (day/night) temperature variations are a key factor behind the ability of Marlborough grapes to retain both fresh, vibrant fruit and crisp, herbaceous characters.



In addition to having a cool maritime climate, viticulture in Marlborough has been developed primarily on sites with moderate-low fertility and noticeable stony, sandy loam topsoil overlying deep layers of free-draining shingle.  These shallow, fast draining, low fertility soils help to produce a lush, aromatic ripe wine because they reduce the vines vigor.  Where a more herbaceous style is desired, sites with greater water retentive soils and moderate fertility are chosen.[1]

The Wine



The 2012 Mohua Sauvignon Blanc is clear with low intensity watery straw-yellow with hints of green around the edges. On the nose it displays classic medium intense aromas of grapefruit, bell pepper, jalapeno, melon rind, granny-smith apple, lemon blossom and chives. On the palate it has medium+ acidity with medium body and a medium+ length finish. While this wine does display the hallmarks of a New Zealand Sauvignon Blanc it isn’t quite as intense and sharp as the 2012 Kim Crawford Sauvignon Blanc, so I preferred this wine. This wine sells for $12-15 retail.


[1] http://www.wine-marlborough.co.nz/

3 comments:

  1. Thanks for the great chemically detailed review! When I smelled this wine, it took me a minute but then it hit me-- tomato leaf aroma... that odor you get from a growing tomato plant when you run your hand through the leaves or just stick your nose into the plant. I love that aroma. Gotta be a pyrazine!

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  2. Thank you for your comment. I don't have a lot of experience in growing tomatoes so I'll have to take your word for it. But generally green notes in wine come from pyrazine and they can be interpreted differently as being like grass, herbs, or in your experience tomato leaf. The next time I am at someone's house and they have a garden, I'll sniff their tomatoes!

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  3. I think the tomato leaf aroma is from a related compound--specifically a 2-isobutylthiazole.... found this with a search for pyrazine and tomato leaf http://www.pyrazinespecialties.com/index_products_info_thiazoles.html
    Very interesting to the chemist in me for all that I do not know!

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