Understanding where aromas in wine come from

A lot of us have done this. Holding up a glass of wine to our nose and smelling the Pandora’s box of different wine aromas and wondering where these aromas come from? Are there lemons and lime in my Pinot Grigio, and have they put plums and raspberries in my Merlot?

Wine is only made from one ingredient, grapes. Well, technically with yeast as well. Citrus, tropical fruits, berries, chocolate, cinnamon, mushrooms, honey, the list is endless for wine aromas. How do they end up in the bottle?

I’m here to explain why you can come across all these different aromas and where they come from. It’s time to delve into the world of winemaking to understand some of the reasons for wine drinking.

There are many factors that contribute to the wine aromas present in your glass. Some will be present when you open the bottle and change as you let the wine open up and let it breathe.

Your nose detects thousands of chemical compounds that the brain will process and identify as certain smells. Everyone has different levels of sensitivity and will relate to different smells depending on culture, foods and even memory. That is why your perception of wines will be different to others.

Aroma compounds in wine are made through the process of fermentation. Not only does it convert sugar to alcohol, but also forms various complex, chemical compounds, which make up the bouquet of the wine. It is this mixture of different aroma compounds that wine lovers associate with the specific character of a grape varietal.

However, wine aromas do not just come from fermentation. Different winemaking processes also add to the aroma profile. Listed below is a breakdown of three categories of wine aromas and how they come about.

PRIMARY AROMAS

Topical fruits, stone and tree fruits, berries and more. Wines are distinguished by their characteristic set of aromas and flavours.

Present in all young wines, primary aromas are the fruit, floral and fresh herb characters in a wine. These compounds (volatile precursor aroma compounds) are mostly found in the skin of the grapes, but also in the juice. Different varietals will have a combination of different compounds that result in their typical aroma profile.

But grapes smell like grapes, right? The reason why you cannot smell and taste these characters by sniffing and tasting the skin of the grapes is because these aroma compounds are often bound by sugar molecules and are only released during the fermentation process. By freeing these compounds from their bound form, they turn into the volatile compounds that we can smell.

Here are some examples of primary aroma compounds:

  • Esters: Fruit (tree fruits and red fruits) and flowers (white blossom)
    • Chardonnay – apple, pear
    • Grenache – raspberry, strawberry
  • Pyrazines: Herbaceous (grass, tomato stalk, capsicum), chocolate and coffee
    • Cabernet Franc – capsicum, stalky
    • Sauvignon Blanc – freshly cut grass
  • Terpenes: Floral (rose, lavender, lilac), sweet (lychee), citrus (lemon, orange)
    • Gewürztraminer – lychee, orange blossom water
    • Muscat Blanc – rose petals
  • Thiols: Fruit (gooseberry, passion fruit, grapefruit, cassis)
    • Sauvignon Blanc – grapefruit, gooseberry
    • Cabernet Sauvignon – cassis

SECONDARY AROMAS

Ever smelt a glass of wine and was transported to a movie theatre enveloped in that warm buttery popcorn smell?

Secondary aromas are derived from malolactic fermentation or by decisions in winemaking involving oak, whether this being fermentation in oak or extended ageing in oak barrels.

Malolactic fermentation is a secondary fermentation that usually occurs after the first (alcoholic) fermentation. This is a bacteria driven fermentation as opposed to yeast fermentation, not only does it produce characteristic aromas, but it also deceases acidity of the wine by converting sharp malic acid (sour green apples) to softer lactic acid (yoghurt). It also adds a creamier mouthfeel to the texture of the wine.

It produces a compound called diacetyl which contributes its hallmark buttery character. When this compound is present with other aromas, it can develop buttery popcorn, caramelised toasted nut and creamed corn aromas. Malolactic fermentation is carried out on almost all red wines because a lot of red wines go through barrel-ageing that complement aromas given off from malolactic fermentation and to prevent post-bottling microbial spoilage. It is also common with Chardonnay winemaking, but less so with other white varietals that want to retain high acidity and their pure fruit profile, hence the term big, buttery Chards.

Wines aged in oak barrels will take on a toasted spice flavours that adds layers to the fruit character – layers like an onion, but won’t smell like one!

Oak contact contributes to sweet baking spice secondary aromas. These are commonly associated with barrel use and these compounds are known as oak lactones.

Oak use can be compared as the “spice rack” of winemaking. Winemakers can control which aromas and how much of it will end up in their wine. Coopers (barrel makers) can tailor-make the barrels to the winemaker’s specifications.

  • Firstly, where will the barrels be made? France, America or Hungary? Each country has barrels with different flavours.
  • Secondly, what is the degree of toasting? Ranges from light, medium, medium plus to heavy toasting.
  • Thirdly, new oak or old oak? New oak barrels impart the most flavour, the more you use an old barrel the less flavour it will give off to the wine. Usually winemakers use a mixture of old and new barrels.

Spice baby, spice! Oak is commonly referred to as a winemaker’s spice rack!

French Oak versus American Oak versus Hungarian Oak:

French

Light Toast                    vanilla bean, caramel, baking spices

Medium Toast              cedar, cigar box, chocolate, baking spices

Heavy Toast                 Crème Brûleé, cedar, cinnamom, ginger, clove

American

Light Toast                    vanilla, coconut

Medium Toast              honey/caramel, toasted coconut, coffee, cocoa

Heavy Toast                 espresso, caramelised sugar, campfire

Hungarian

Light Toast                    vanilla, herbs, sweet spice

Medium Toast              butterscotch, banana, sweet spice

Heavy Toast                 vanilla, butterscotch, toffee, molasses

TERTIARY AROMAS

The fruit spectrum can come in a range of styles, fresh, stewed, jam, dried? Tertiary fruit aromas cover the concentrated cooked fruits spectrum.

These are aromas that have developed from bottle ageing. Over the years the aromas present in the wine will change and develop complexity.

This is only suited for wines that have been made for ageing. Wines that are meant to be consumed young will develop flavours that are not palatable, for example the fresh grassy notes and capsicum character of a New World Sauvignon Blanc will develop into canned asparagus aromas, not at all pleasing on the nose.

Desirable bottle-aged characters include:

  • Red or dark fruits initially in the wine will evolve into stewed, jammy fruit characters
  • Development of toasted nutty richness
  • Cedar or cigar box
  • Pungent spices
  • Dried leaves or tobacco
  • Some white wines like Riesling can develop straw and kerosene aromas

These all contribute to the complexity of the bouquet and will often complement the oak characters that also age with the wine.

If you want to learn more about the characteristic flavours of wine, check out these 12 common grape varietals, their aroma profile and more.

A heady combination of bottle and barrel aged spice characters can be displayed in Bordeaux blends.

OTHER AROMAS

  • Sulphur compounds contribute to minerality aromas like chalk, flint and wet pebbles.
  • Yeast Autolysis: bread-like, brioche, nutty sweetness characters on the nose form from extended contact with yeast lees (dead yeast cells, yum!). Prime example is a Vintage Champagne.
  • Botrytis a.k.a Noble Rot: Like its name it’s a style of wine that uses a fungi; Botrytis cinerea that infects and dehydrates the grapes whilst still on the vine and increases the sugar levels. The result is a late harvest sweet wine that tastes like honey, dried fruits, ginger and beeswax. A famous wine for this style is Tokaji Aszu from Hungary and Sauternes from Bordeaux.

“Baked bread, buttery and honey-like aromas with a hint of toasted flaked almonds” – sound like a tasting note to you?

So now you know that winemakers have not been infusing vanilla pods in their wine. Whatever you smell out of the glass was always present in the grape. They were just dormant until the fermentation process released them from their bound form. With the help of oak and bottle ageing, you have an aroma bomb that will keep your nose going back and forth between glasses.

The next time you hear the question where do wine aromas come from, you will be able to tell them how!

END

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