For those of us who don’t have a degree in Chemistry (me included), the relevance of Pyrazine to wine is that it gives it a “green” taste / aroma.
It doesn’t take much for you to detect it either, around 2 parts per trillion to be exact.
It’s stated that a single grape amongst tonnes of grapes will change the aroma of the entire batch of juice. Powerful stuff indeed!
If you want to get REALLY nerdy about it (and I’m sure you do) there are a few types of Pyrazine found in fruit and veg:
Isobutylmethoxpyrazine – found in bell pepper
Isopropylmethoxpyrazine – found in green asparagus or peas
Sec-butylmethoxpyrazine – found in beetroot
This all starts making sense now when talking about aromas in wine! Depending on where it’s found, Pyrazine can either be pleasant or unpleasant. It almost defines a lot of Sauvignon Blanc wines (in a good way); so the next time you are tasting a New Zealand Sauvignon, pay attention to the green aromas. That’s Pyrazine.
The problem is that in red wines, it will come off as being vegetal (not so desirable), especially in cooler vintages. When not ripened properly, Cabernet Sauvignon is particularly susceptible to high levels of Pyrazine. In warmer climates, Pyrazine takes more of a backseat as grapes become riper and develop aromas which mask the vegetal scents. That being said, the burden still falls on vineyard managers to ensure grapes are picked at the correct ripeness, and winemakers to make sure levels are kept in check.