Pyrazines—too much of a good thing and they’re a fault; absent in varieties like Sauvignon Blanc and they leave something to be desired. In relation to bitterness, pyrazines can be the source of a flaw or fault, but that’s just one of many ways they can impact wine flavor.

Ask any maker of Bordeaux varieties, someone who grows grapes in a marginal climate or experiences a colder vintage, about their concerns, and they’ll surely count elevated pyrazines among them. Admittedly, pyrazines are a double-edged sword. Without them we wouldn’t have the expansive range of wine styles that are possible from Sauvignon Blanc or the markers that help us identify the family of Bordeaux varieties and the likes of Carmenère.

But in the extreme, pyrazines dominate wine at the expense of other varietal flavors. We’ve all tasted them—from pungently herbaceous boxwood (the polite reference to cat pee) and jalapeño pepper in Sauvignon Blanc to rank green bell pepper or even weeds in red wines that haven’t achieved physiological ripeness.

Pyrazines are the family of volatile organic compounds most widely represented in food aromas. They are categorized into three groups, and we’re concerned with those present in the natural state in plants and, more specifically, grapes. The methoxypyrazines found in grapes include 3-isobutyl-2-methoxypyrazine (IBMP) which is most commonly found in the Capsicum or pepper family and characterized by flavors of green peas, bell pepper, tomato leaf and asparagus. IBMP is associated with rankness in wine and differs from capsaicin, a compound only found in the placenta and seeds of peppers.  Read the article here – Pyrazines.