Wine Aroma: The Art Of Sensory Science

Wine aromas are influenced by a variety of factors, from the type of grape to the ageing process. The human nose can detect thousands of unique scents, and when it comes to wine, smelling is just as important as tasting. The aroma of a wine can give clues about its ingredients, fermentation techniques, and storage conditions.

The aroma or nose of a wine refers to the smell, which can be floral, citrusy, fruity, vegetal, earthy, or spicy. These aromas are the result of volatile compounds that are present in the grapes and are released during the fermentation process. Different grape varieties have different aroma compounds, and these can be enhanced or subdued depending on the winemaking process.

The ageing process also plays a crucial role in developing a wine's bouquet, which refers to the smells that arise from the chemical reactions of fermentation and ageing. During ageing, new aromatic compounds can form, and the existing compounds can break down and change, resulting in a more complex aroma profile.

Grape variety

The aroma of grapes is produced by various enzymes, including terpene synthases, O-methyl transferases, carotenoid cleavage dioxygenases, and cytochromes P450. Muscat and Gewurztraminer grapes, for instance, contain high levels of terpenoids, resulting in a distinct floral aroma. On the other hand, Sauvignon wines have higher levels of methoxypyrazines, which contribute to their capsicum aroma.

Terpenes, a class of volatile compounds, play a crucial role in the varietal aroma of grapevines. The terpene synthase gene family has expanded in grapevines, emphasizing the significance of terpenoids in this species. Monoterpenols, in particular, exhibit a wide concentration range in grapes and wines, suggesting their role as varietal aroma compounds.

Additionally, the diverse spectrum of aromas in different grape varieties is a reflection of the vine's adaptation to its ecological conditions and competition with other plants. The interaction between volatile compounds and sugars in wine further influences the aroma. Through hydrolysis, these compounds revert to their aromatic form, which our olfactory receptors detect when tasting wine.

Fermentation

The key ingredient in fermentation is yeast, which can give a wine hints of fresh-baked bread, butter, cream, and cheese. Yeast also produces esters, which are aromatic compounds that contribute delicate fruity, citrusy, or floral aromas to a young wine. Acetaldehyde, created by yeast, can enhance fruity aromas in wine. In high concentrations, however, acetaldehyde may yield unwanted bruised apple-like aromas and flavors.

The type of fermentation vessel can also influence how fermentation proceeds and the finished wine. Oak, for example, allows for gradual oxidation of the juice and wine, while the wood usually softens the impact of tannins and acid, resulting in a rounder wine with a distinct character.

The beginning of fermentation involves a lot of biodiversity, with many different types of yeast competing for resources. If allowed to ferment, each type of yeast leaves behind its own particular signature of flavor and aroma compounds.

The ethanol produced through fermentation acts as an important co-solvent to the non-polar compound that water cannot dissolve, such as pigments from grape skins, giving wine varieties their distinct color, and other aromatics.

Ageing

The ageing process can enhance or diminish a wine's aroma, depending on the type of wine. Wines that are designed to age will lose part or all of their primary aroma and develop new aromas over time. On the other hand, wines that are meant to be enjoyed immediately may not develop much of a bouquet, and ageing them may cause their fresh aromas to diminish.

The ageing process can also be influenced by the type of container used, such as bottles, barrels, or tanks, as well as the type of wood used for barrels. Ageing in wooden barrels can infuse the wine with woody flavours, as well as coconut, cloves, and vanilla flavours. Ageing in terracotta tanks or wood can create compounds like acetic aldehydes, resulting in flavours like nuts, caramelised sugar, or dried fruits.

The longer and more extensive the ageing process, the more a wine's aromatics will be influenced by tertiary aromas, which are associated with the bouquet of a wine. These tertiary aromas can include oxidative character traits like coffee, caramel, toffee, and cocoa, or reductive notes that lean towards earthy nuances like damp forest floor, mushrooms, or vegetable-like components.

In conclusion, ageing plays a crucial role in the development of a wine's bouquet and can either enhance or diminish its aroma depending on the type of wine and the ageing process used.

Serving temperature

When wine is served too cold, its aromatic compounds are muted as fewer volatile compounds are released. Conversely, serving wine at a warmer temperature allows these compounds to be released more easily, giving you the opportunity to experience the wine's full aroma.

The ideal serving temperature depends on the type of wine. Generally, white wines are served at cooler temperatures (8-12°C), while reds are served at room temperature or slightly cooler. Sparkling wines are typically served at a chilly 40°F to 45°F (4°C to 7°C).

For light-bodied white wines, such as Sauvignon Blanc and Pinot Grigio, the recommended serving temperature is between 45°F and 50°F (7°C to 10°C). This cooler temperature preserves their zesty acidity and vibrant fruitiness.

Full-bodied white wines, such as Chardonnay and Viognier, are best served at a slightly warmer temperature, ranging from 50°F to 55°F (10°C to 13°C). This allows their complex flavours to unfold.

Light-bodied red wines, such as Pinot Noir and Gamay, are best served at a slightly cooler temperature than room temperature, typically between 55°F and 60°F (13°C to 16°C). This temperature range allows these wines to express their delicate red fruit notes.

Medium-bodied red wines, such as Merlot and Zinfandel, should be served at around 60°F to 65°F (16°C to 18°C) to bring out their rich texture and balanced flavours.

Full-bodied red wines, such as Cabernet Sauvignon and Syrah, are best enjoyed at 63°F to 68°F (17°C to 20°C). This warmer temperature accentuates their bold structure and tannins.

It's worth noting that personal preference also plays a role in serving temperature. While these guidelines provide optimal temperature ranges for different types of wine, some people may prefer their wines cooler or warmer. Experimenting with different temperatures can help you discover your preferred wine-drinking experience.

Glass shape

The shape of a wine glass can have a significant impact on the drinking experience, influencing not only the aroma but also the flavour and overall enjoyment of the wine. While the glass's design may seem purely aesthetic, it is, in fact, a meticulously crafted tool that enhances the wine's qualities.

The bowl, or main body of the glass, plays a critical role in the wine's exposure to air (aeration) and the concentration of aromas. Larger bowls are typically suited for red wines, as they allow the wine to breathe and develop a richer bouquet. On the other hand, narrower bowls are preferable for white wines, as they preserve their delicate aromas. The size and shape of the bowl also affect the release of ethanol vapours, which can interfere with the wine's aroma. Scientists have found that different glass shapes and temperatures can significantly alter the bouquet and finish of the same wine.

The rim of the glass is another important feature. A thinner rim allows for a smoother flow of wine onto the tongue, enhancing the drinking experience. Tapered rims are also designed to direct the flow of wine and focus the aromas.

The stem of the glass serves multiple purposes. It acts as a handle, allowing the wine to be held without transferring body heat, thus maintaining the optimal temperature. The stem also facilitates swirling, which enhances aeration and aroma release without smudging the bowl.

The base of the wine glass provides stability and supports the weight of the glass when filled with wine. It varies in size and weight, contributing to the overall balance and feel of the glass.

While the specific effects of glass shape on wine aroma are still being studied, it is clear that the design of a wine glass goes beyond aesthetics, influencing the wine's aroma, flavour, and overall sensory experience.

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