Why Doesn’t Wine Just Smell Like Grapes?

Photo by Helena Lopes from Pexels

After visiting a winery with friends, I once made the pretentious mistake of scoffing when someone asked what kind of flavoring was used to give the wine an almond smell — as if it was as simple as putting a flavor shot in a Starbucks drink. But when my laughter subsided, I realized they weren’t joking. I got down from my high horse and realized that this is a perfectly normal assumption. How else could fermented grape juice smell like almonds?

This is the magic of wine. From grapes we can get aromas of almonds, pears, lavender, rocks, pineapple, even gasoline.

But let’s back up. 

What is an aroma? How is an aroma different than a flavor or a taste? The way scientists describe these words is different than how we use them in everyday language.

An aroma is what you smell, either with your nose or with your mouth. (Yes, your mouth. We’ll get to that below.)

A taste is what you perceive in your mouth to be sweet, salty, sour, bitter, and umami. This is different from the mouthfeel, which is, literally, the way something feels in your mouth. Mouthfeel is a sensation, not a taste.

A flavor is a multisensory experience that occurs in your mouth when you eat or drink. It includes taste, aroma, and tactile sensations. Some scientists suggest that flavor even includes visual and auditory cues that we perceive when eating or drinking.

So let’s take a few examples to understand this better. When you drink red wine, you are feeling and tasting the tannins. This is because tannins are both astringent (a feeling) and bitter (a taste). However, tannins are non-odorous compounds; they do not have a smell.

But if you consider the aromas of that glass of red wine, you’ll start to understand how the words flavor, taste, and aroma can get mixed up easily. 

First, you smell the wine. You are taking in its aromas. You might get smells of blackberry and lavender. When you take a sip of the wine, you might notice the taste of mint. But this might actually be the flavor of mint; that is, the taste and the aroma of mint.

Why? Because we smell through our mouths too, not just our noses. Smelling through your nose is called orthonasal olfaction, and smelling through your mouth is called retronasal olfaction.

Vilela and Cosme, 2016

There is a passageway that allows smells to travel from your mouth to your nose, where it is processed by the olfactory bulb in your brain. What we so often think of as being a taste is actually a smell. This explains why when you’re sick and have a stuffy nose, your ability to “taste” food diminishes. In fact, you weren’t really tasting the food after all; you were smelling it.

Now that you’ve got down the science of sniffing, let’s talk about where wine aromas come from. There are three different kinds of aromas found in wine: primary, secondary, and tertiary.

1. Primary aromas come from the grape variety.

This could be fruit smells, flower smells, or herb smells. For example, Cabernet Sauvignon is known to have a green pepper smell. Viognier is known to have a rose smell. Sauvignon Blanc can have tropical fruit smells. These aromas come from various chemical compounds in the grape itself. 

2. Secondary aromas come from the fermentation process.

These are mostly the smells that come from the yeast strain. This is what gives that yeasty, bready smell. It can also be buttery or milky (from malolactic fermentation). Sometimes, when wines are left to age on the lees (the dead yeast cells), this can impart more secondary aromas.

3. Tertiary aromas come from the aging process.

These are the smells that get revealed during aging, like leather, mushrooms, tobacco, nuts, and even dried fruit or complex spices. Tertiary aromas arise due to the wine’s interaction with oxygen, which can seep into the wine in tiny amounts through the barrel or the cork (if already bottled). If the wine is aged in barrels, the oak will also impart an aroma to the wine.

Another distinction to make in sniffing science is the difference between wine aromas and wine bouquets. Generally, when people talk about aromas, they’re referring to the primary aromas. When people talk about the wine bouquet, they’re talking about the secondary and tertiary aromas. This is why you’ll hear the term “bouquet” used more for aged wines.

It’s important to note that not all of these aromas are good. Sometimes there can be off-flavors in the wine, and these can arise from undesirable types of yeast (such as Brettanomyces), acetic acid bacteria, a lack of nitrogen in the grape must, or even from the cork. 

And there are also some instances when the aroma doesn’t quite fit into the category of primary, secondary, or tertiary. 

Photo by CHUTTERSNAP on Unsplash

Remember that almondy wine? It was a Sauternes wine, which is a type of wine made in the Bordeaux region from white grapes that have been attacked with Botrytis cinerea, a fungus also known as “Noble Rot.” 

The almond smell could have been from a compound called Sotolon, which arises in Botrytised wines during the aging process, likely due to the interaction of oxygen on the wine. In this case, yes, it would be a tertiary aroma. 

But it might also have been due to something entirely different. When the Botrytis fungus attacks the berry, the berry responds by producing benzyl alcohol, which is toxic to the Botrytis. In return, the Botrytis produces the enzyme necessary to degrade the benzyl alcohol into benzaldehyde —  the compound responsible for the bitter almond aroma.

This benzaldehyde aroma is not really from the grape itself under healthy conditions. It is the biochemical response of the grape to the fungus, and the subsequent counter-attack by the fungus, that leads to this smell. 

In the end, wine aromas are incredibly complicated. Scientists don’t have all the answers, but we do know there are plenty of natural mechanisms within the berry itself, during fermentation, or during aging that influence wine aromas and flavors.

And to my friend’s credit, sometimes these aromas are actually from a flavored syrup. It might not be as straightforward as a sugary Starbucks flavor shot, but it’s not a wild deviation. There is an infamous wine syrup that’s probably in most red wines under $10. This sugary grape juice concentrate, Mega Purple, is meant to impart a smooth sweetness and intensify the wine’s color.

In my next posts, I’ll be doing a deeper dive into some of the common primary aroma families (those that arise from the grape variety), as well as wine faults. If you’re wondering how wine can smell like green peppers, guava, or even rotten eggs, follow my Medium blog, The Wine Press!

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