If you think you’re tasting raspberries for example, odds are you’re getting a little sweetness, a little sourness, and a big hit of raspberry aroma to the schnozz. You’re not imagining it, and some European dude in a waistcoat didn’t make it up. The reason wines smell the way they do is tied up in chemistry, namely the organic molecules present in grapes that are transformed during fermentation and beyond. 

The first aromas you’re likely to spot in wines are primary fruit aromas. Primary meaning the compounds you’re smelling are in the original grape. They smell like fruits, because they are in fruits.

Some Chardonnay, for example, is described with tropical fruit aromas. The grapes naturally contain aroma molecules called thiols (amongst many others). Those very same thiol molecules are found in fruits like passionfruit, also. They smell the same, because they are the same. Unfermented Chardonnay grape juice might not smell all that passionfruit-y though. Sugars in grapes are converted to alcohol through fermentation. Most aroma compounds are smaller, volatile molecules– that’s why they enter the air and can be inhaled. Large sugar molecules bind aromas, so when sugar is fermented ‘out’ of the wine, aroma molecules are freed up to hit your nose.

That’s why aromas associated with plants are detectable (and delectable) in wine. Wine comes from plants, so it’s no stretch to conceive of other planty scents entering the fray– flowers, herbs, spices. As for the decidedly non-plant aromas? Earth, minerals, bread, gun powder, kerosene, leather, meat, smoke, butter. These typically fall into the category of secondary or tertiary aromas.

Secondary aromas are those that arise because of chemical reactions involved in fermenting grapes. Yeasts are used to carry out fermentation, freeing up aroma compounds and changing their chemical composition, explaining the presence of smells we wouldn’t expect.

Plus, yeast itself can bring flavours to wine we recognise from other applications. Baking uses the same species (though different strains) of yeast, explaining bready or biscuity character.

Wines aged on lees (dead yeast cells) will pick up a lot of this character, alongside other possible aromas like hay, or nuttier notes. Malolactic fermentation is another chemical reaction that alters the compounds in wine, converting malic acid to lactic acid (found in dairy products), explaining buttery or creamy notes.