Have you ever detected a hint of green pepper in your Cabernet Sauvignon or Cabernet Franc? Whether you mind this or not, winemakers don't tend to as it lends the wine unripe characteristics.
This attribute is caused by a chemical compound called 3-isobutyl-2-methoxypyrazine, or ‘pyrazine’ or IBMP for short. Another compound from the pyrazine group, 3-isopropyl-2-methoxypyrazine, is responsible for the grassy, herbaceous and asparagus aromas in Sauvignon blanc.
IBMP is actually manufactured by grapes to deter predators from eating them before the fruit and seeds are ripe enough for dispersal and survival. So, if critters find this chemical unpleasant at trace concentrations, no wonder we don’t like it either! Although most of the IBMP is metabolised throughout the growing season, there is a risk of small amounts remaining in the fruit if it isn’t exposed to enough UV. Unlike acid which depletes with temperature, pyrazines are reduced by light exposure.
There was a time in the past when Margaret River struggled somewhat with managing these pyrazine descriptors, however the region worked hard and smart to resolve this issue. For a long time now, we’ve used early season leaf removal in the fruit zone to allow sufficient time and sun exposure to deplete IBMP to undetectable levels.
You may still pick up on some pleasant herbaceous notes in your Cabernet, however the culprit is unlikely to be capsicum these days!