Wine Aromas & Flavors---What Causes Them?

 

      As grape sugar is converted by yeasts into alcohol, thousands of chemical by-products are produced

This is the final article in September’s series on the grape harvest.  Today’s blog discusses aromas & flavors of wine that are a direct result of the fermentation process.   How can a wine smell like a banana?  Why do Sauv Blancs often have a grassy profile?   What is it about Champagne that causes many to have almond nuances?   Did you know that all of these aromas and flavors occur because of chemical reactions during fermentation?  Let me explain.  

               Banana flavors & smells are due to isoamyl acetate produced during fermentation

First, let’s talk about the banana smell and taste.  This is a direct result of the fermentation process where yeasts change grape sugar into alcohol.  The banana profile is the result of a chemical compound by the name of isoamyl acetate, a by-product of yeasts during fermentation.   (Isoamyl acetate is used as an artificial banana flavoring in desserts).    These banana aromas & flavors can be found often in Chardonnay and Pinot Gris, especially from warm climates where grapes are super ripe.  Again, this is a result of the chemical changes during fermentation.

                                Aldehydes form during fermentation & are also present in grass

Have you ever wondered why your Sauv Blanc is reminiscent of freshly mowed grass?   The classical grassiness nose and taste is due to chemicals called aldehydes.  These compounds, released during fermentation, evoke the smell of just-cut grass.   Sauv Blanc grapes have the ability to produce high levels of aldehydes.  Similarly, grass contains elevated levels of this highly fragrant chemical and cutting the grass releases it into the air.

                                One of fermentation's many by-products is benzaldehyde

The almond profile in the real-deal French Champagne is also produced by yeasts as they change grape sugar to alcohol during fermentation.  During the process of making Champagne the fermenting grape juice is often stirred.  The chemical benzaldeyde  is released during the fermentation process and it is dramatically heightened during the stirring (“battonage”).   Benzaldehyde tastes and smells like almonds.

 

In summary, during fermentation yeasts eat the sugar of the grapes and convert it into alcohol.  In this process of fermentation, thousands of various chemicals are produced by the yeasts activities and they often influence the aromas and tastes of wine.

How Can Wine Smell like a Banana?

                 Banana, green apple & gooseberry profiles are the result of chemical reactions

Why in the world does a wine taste or smell like any fruit other than a grape?  This is the second article in a blog series on the science behind certain flavors and aromas in wine.  This particular article will discuss three fruit flavors/fragrances that can appear in wine.  In fermentation, yeasts eat the sugar in the grapes and convert it to alcohol.  In this process thousands of various chemical compounds are produced.  All three fruit flavors below are a result of these complex chemical processes.

Banana

The banana-like smell and taste is a result of a chemical compound by the name of isoamyl acetate, a by-product of yeasts during fermentation.  The isoamyl acetate also occurs naturally in the banana plant, as well as in pears.  It is present in most wines, however, it is below the threshold of one’s ability to taste it.  It should come as no surprise that artificial banana flavoring is made from isoamyl acetate.

This banana smell and taste can appear in both white and red wines.  Aromatic white wines that are fermented at cooler temperatures (lower temperature enhances the amounts of isoamyl acetate) often display ripe banana notes.  For example, that banana nuances can often be found in Chardonnay, Pinot Gris and Albarino.  Beaujolais is one of the few red wines that has a banana profile.

Green Apple

This flavor and smell profile found in wines is due to the lactic acid which is created during malo-lactic fermentation.  Lactic acid gives off green apple-like scents and flavors, in addition to a creamy mouth feel.  Wines that have pronounced green apple character are classically cool climate dry whites such as Chardonnay, Riesling and Gruner Veltliner.

Gooseberry

Like green apples and banana nuances, this flavor and aroma is not part of the grape.  Gooseberry is created during alcoholic fermentation and is a by-product of yeast activity.   This fruit is typically less sweet so its taste is on the tart side (think pucker),  but gooseberries can also have a slightly floral scent.  Generally found in aromatic whites, gooseberry is classically associated with Sauvignon Blanc (particularly those from cool weather regions such as coastal New Zealand, or France’s Loire Valley).

Keep in mind that each person has a different innate level of tasting various substances.  It doesn’t matter what you taste or don’t taste in a wine.  The only thing that counts is if it pleases you.