Wine and the threshold of perception

Describing wine can be a challenging task

Where do you start, that smell is on the tip of your tongue but you can’t quite find it in your memory.

Finding consistent things to identify one grape as being different from another is hard because everyone has a slightly different palate and a different set of flavour experiences to draw upon.

As science continues to evolve though we can dig down into grapes to break apart the mix of unique chemicals and compounds that contribute to what you smell and taste in your glass.

Many of these compounds are below our thresholds of perception, but there are groups of them that have a big impact on the unique characteristics that differentiate a Sauvignon Blanc from a Pinot Grigio.

From Thiols to Terpenes, they have wildly complex scientific names but they represent smells and flavours familiar to all of us and can help us to describe and identify different wines.

Thiols can be both positive and negative, the positive side are known as volatile thiols. These are most notably found in Sauvignon Blanc, showing themselves as aromas and flavours such as grapefruit, passionfruit, gooseberry, guava and cat pee.

They have been a big contributor to flavours of Marlborough Sauvignon Blanc but they contribute to the blackcurrant character in Cabernet Sauvignon (Sauvignon Blanc is a parent of Cabernet Sauvignon) and they also contribute to the flavours in Riesling, Semillon and Merlot.

Terpenes are quite unique in that they can be smelt in the physical grapes prior to fermentation and carry on through to the final wine. They appear in quite high concentrations in grapes which helps to explain why they are so intense and so easy to identify. They contribute the floral notes in wines such as Muscat (including Moscato), Gewurztraminer, Viognier and Riesling. They can also contribute spice such as the ginger notes often identified in Pinot Gris. If you enjoy any of these grape varieties then it is a good idea to explore the others mentioned as it is such a unique and intense set of flavours. While these wines are often derided for their fruit sweetness or actual sugar sweetness there are plenty of fantastic dry, yet full-bodied examples.

Pyrazines appear in a pretty small subset of grapes, but again they are a distinct and easy to identify. The capsicum/green pepper that you see in Sauvignon Blanc, Cabernet Sauvignon, Cabernet Franc and less so in Merlot are coming from this group of compounds.

While those grapes are obvious, it is worth exploring other less well-known grapes such as Verdejo from Spain (known as Verdehlo in Australia), which tend to be subtler in their expression but are still crisp, juicy whites that provide some variety in your repertoire.

A good way to clearly identify these elements and understand whether you like or dislike them is to get three bottles of wine, each displaying one of the compounds clearly to compare with a group of friends.

For example, Wild Rock Sauvignon Blanc (Thiols), Skillogalle Gewurztraminer (Terpenes) and a De Iuliis Verdehlo (Pyrazines) is a good cross section of whites to compare and contrast.