The Magic Of Wine Aromas: Unveiling Their Sources

Wine aromas are derived from a combination of the grape variety, the winemaking process of fermentation and aging, and the evolution of the wine over time. The human tongue can only perceive basic tastes, but the olfactory bulb can detect a wide array of fruit, earthy, leathery, floral, herbal, mineral, and woody flavours present in wine. These aromas are the result of thousands of different volatile compounds, which can be classified into primary, secondary, and tertiary aromas. Primary aromas come from the grape variety, secondary aromas are derived from the winemaking process, and tertiary aromas develop as the wine ages.

Wine aromas are naturally occurring

Primary aromas come directly from the grape variety and are commonly associated with young wines. These aromas typically fall into the categories of fruit, herb, and flower smells. For example, the primary aroma of Cabernet Sauvignon is commonly noted for its smells of raspberry, green peppercorn, and sometimes violet. The primary aroma of Gewürztraminer is rose or lychee, while grapefruit, boxwood, or freshly cut grass may be characteristic of Sauvignon Blanc.

Secondary aromas, on the other hand, arise during the winemaking process, particularly during fermentation. Some acids synthesized by yeast during fermentation can contribute to the smell of wine. For example, acetic acid, which has a vinegar smell, contributes to the fragrant odour of wine in small concentrations but is considered a defect if its concentration increases. Lactic acid, produced during malolactic fermentation, brings a buttery or creamy character to some wines, such as Chardonnay.

Tertiary aromas develop as wine ages and can be influenced by factors such as exposure to oxygen, the use of oak barrels, and the practice of heating or cooking the wine. Aging wine in oak barrels can impart aroma compounds found in the oak, such as vanilla, coconut, clove, and cinnamon. Exposing wine to oxygen can produce positive-smelling bouquets, including the aromas of hazelnut and roasted peanut.

In addition to these primary, secondary, and tertiary aromas, wine can also exhibit what are known as "estery" aromas. Esters are volatile flavour compounds created by reactions between alcohols and acids. They are responsible for primary fruit flavours found in very young wines, such as pear-drop candy or a mix of banana and pear flavours.

The wide array of aromas found in wine, from fruity and floral to earthy and woody, are made possible by the diverse compounds present in the grapes and the complex chemical reactions that occur during winemaking and aging.

Aroma compounds are found in wine

The aroma of wines is the result of the contribution of some hundreds of volatile compounds. The diversity of aromatic compounds in wine is immense and ranges in concentration from several mg l−1 to a few ng l−1. The main compounds responsible for the most intense aromas in Sauvignon Blanc wines have been assumed to be methoxypyrazines and varietal thiols.

Higher alcohols, acids and esters are quantitatively dominant in wine aroma and are important in the sensory properties and quality of wine. Small amounts of higher alcohols contribute positively to wine quality, while excessive amounts may detract from it. Esters contribute to wine odour and relatively high concentrations of fatty acids give an appreciable strong odour.

The specific compounds in wine are not clear. It is important to study the chemical and biochemical changes during fermentation and storage. Nevertheless, further research into the sensory impact of wine aroma compounds, both alone and in mixtures, will be focused on.

Wine bouquet is derived from the winemaking process

Wine aromas and bouquets are not exactly scientific terms, but they are useful for classifying the origin of wine smells. A wine aroma is derived from the grape variety, while a wine bouquet is derived from the winemaking process of fermentation and aging.

The process of fermentation creates a group of bouquets called secondary aromas. Fermenting wine turns grape sugars into alcohol, and this is commonly associated with a specific yeast called Saccharomyces cerevisiae, which is also essential in baking and beer brewing. The yeast itself lends the wine an aroma akin to freshly baked bread or butter. Other secondary aromas include cultured cream (yoghurt), beer (found in wines aged on the lees), aged cheese (parmesan), and horse sweat.

Aging wine introduces elements that add to or alter the aroma compounds in wine after it’s fermented. This group of bouquets is called tertiary aromas. The most important element of aging is exposing wine to oxygen, which in small amounts, produces positive-smelling bouquets such as hazelnut and roasted peanut. Another common element is the use of oak barrels, which introduce oxygen (nuttiness) as well as adding aroma compounds found in oak. A less commonly used element of aging is the practice of heating or cooking a wine, which causes a Maillard reaction where sugars and amino acids react with one another, turn brown, and caramelize. This creates flavours such as roasted almond, clove, and baking spices.

Wine aromas are classified as primary, secondary, and tertiary

Primary aromas come from the grape variety itself and are associated with the smell of certain grape varieties. They are also called "varietal aromas". For example, the typical varietal aroma of Gewürztraminer is rose or lychee, while grapefruit, boxwood, or freshly cut grass may be characteristic of Sauvignon Blanc. These aromas are typically in the realm of fruit, herb, and flower smells and come naturally just from the grape. Primary aromas can be further divided into several families of aromatic compounds: monoterpenes, norisoprenoid derivatives, methoxypyrazine, thiols, and lactones.

Secondary aromas are derived from the winemaking process, including techniques such as fermentation, oak aging, and malolactic fermentation. Some acids synthesized by the yeast during fermentation can contribute to the smell of wine. For example, acetic acid has a vinegar smell, and in small concentrations, it contributes to the fragrant odor of wine, but if its concentration increases, it is considered a defect. Another example is lactic acid, which brings a buttery or creamy character to some wines.

Tertiary aromas develop as wine ages. Exposing wine to oxygen is the most important element of aging, as oxygen produces positive-smelling bouquets, including the aromas of hazelnut and roasted peanut. The use of oak barrels is another common element of aging, as they introduce aroma compounds found in oak, such as vanilla, clove, and cinnamon. Bottle age also develops interesting new notes in wines, such as nuttiness, smoke, honey in whites, and leather, tobacco, or forest floor in reds.

Wine aromas are influenced by oak

Wine aromas are influenced by a variety of factors, one of which is oak. Oak has been an integral part of winemaking since ancient times, when it was used by the Romans for storing and transporting wine. Today, oak is selected deliberately by winemakers to impart specific flavours, aromas, and complexity to their wines.

Oak affects wine in several ways, including adding flavour compounds, allowing for controlled oxygen intake, and providing an environment for metabolic reactions that influence the wine's texture and taste. The use of oak barrels in winemaking can be fine-tuned to influence the texture, aroma, and flavour of the wine.

The type of oak used, such as American or French oak, impacts the resulting flavours and aromas. American oak (Quercus alba) is known for imparting notes of vanilla and coconut, while French oak (Quercus robur) lends flavours of hazelnut and smokiness to the wine. The origin of the oak, including regional variations and the species of oak, also plays a role in the resulting aromas.

The preparation of the oak barrels is another critical factor. The drying and toasting processes affect the flavours and aromas extracted from the oak. Higher toast levels, for example, amplify butterscotch notes in American oak and smokiness in French oak. The level of toasting can be controlled by the cooper, with typical levels being light, medium, and dark. The newer the oak barrel, the more pronounced its influence on the wine, as with each use, the barrel loses some of its flavour-imparting properties.

The size of the barrel is also a factor, with smaller barrels having a greater impact due to a higher percentage of the wine coming into contact with the wood. Additionally, the age of the barrel matters, as older barrels may no longer impart any flavours but can still allow for a small amount of oxygen exchange, influencing the wine's chemical conversions during fermentation and maturation.

The time spent ageing the wine in oak barrels, known as barrel maturation, is another variable that winemakers can adjust. The longer the wine is in contact with the oak, the more influence the oak will have on the final product.

In conclusion, oak plays a significant role in influencing the aromas and flavours of wine. Winemakers carefully select the type of oak, preparation methods, barrel size, and ageing time to achieve their desired results. The use of oak in winemaking is a complex and nuanced process that contributes to the unique characteristics of each wine.

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