Unveiling The Complex Aromatic Secrets Of Wine

Wine is full of many aromatic compounds, with around 800-1000 different compounds present in a single wine. However, not all of these are above the threshold where we can smell and identify them. The human sense of smell is limited, with most people only being able to identify one or two distinct aromas in a wine. However, professional wine tasters can identify a wider range of aromas by breaking them down into three broad categories: primary, secondary, and tertiary aromas. Primary aromas come from the grape variety itself, secondary aromas are derived from the winemaking process, and tertiary aromas develop as the wine ages.

Primary, secondary and tertiary aromas

Wine contains a stunning array of flavours and aromas, almost all of which are not present in the pre-fermented liquid. Wine aromas are commonly split into three broad categories: primary, secondary, and tertiary. These three levels of aromas evolve over the course of a wine's life.

Primary Aromas

Primary aromas come from the grape variety itself. They are the most obvious to detect in young wines and are often what sparks interest in wine drinkers. For red wines, primary aromas include black, red, and dried fruit, as well as red fruit or berry aromas like raspberry or red currant. White wines offer scents and flavours of green apples, citrus, tropical and stone fruits, and underripe fruits. Some primary aromas can be herbaceous, with a well-known example being the green bell pepper characteristic of Cabernet Sauvignon or Cabernet Franc. Floral aromas are also common in primary notes, including rose, violet, blossom, or honeysuckle.

Secondary Aromas

Secondary aromas are derived from winemaking processes like fermentation and aging. These can include biscuit and yeasty notes that appear from lees stirring and autolysis (the effect when yeast dies off), or the buttery popcorn aroma that’s a byproduct of malolactic fermentation in many Chardonnays. Oak aging imparts characteristics like vanilla, clove, smoke, coconut, or even coffee.

Tertiary Aromas

Tertiary aromas develop when wine is aged in an ideal environment. In red wines, fresh ripe fruit starts to transform into stewed or dried fruit, and tertiary aromas of tobacco, earth, and mushroom emerge. White wines develop dried apricot, orange marmalade, and Sherry-like notes of almonds and candied fruit. Other tertiary characteristics include nutty aromas and complex spices like nutmeg, ginger, and petrol.

The human sense of smell

The sense of smell functions by detecting odours through receptors in the nasal cavity, which transmit signals through the olfactory system. Glomeruli aggregate these signals and send them to the olfactory bulb, where they interact with brain regions responsible for smell identification, memory, and emotion. This process allows us to distinguish a vast array of scents, with recent research suggesting that humans can differentiate over one trillion unique odours.

The sense of smell is closely linked to taste, with the olfactory receptors in our nasal passages contributing significantly to our perception of flavour. This is particularly evident during the process of mastication, where the tongue manipulates food to release odourants that enter the nasal cavity during exhalation, contributing to our overall sensory experience of the food.

The sense of smell also plays a crucial role in social interactions, allowing us to identify emotional states, assess genetic compatibility, and even detect threats. Furthermore, it has been shown that emotions themselves can be transmitted through smell, with emotions such as happiness, fear, and disgust being contagious through olfactory cues.

While the human sense of smell is impressive, it is important to note that it can be influenced by various factors. For example, mental and physical health, smoking, and training can all impact our olfactory sensitivity. Additionally, certain odours may activate both the olfactory and somatosensory systems, blurring the lines between smell and other sensory experiences.

How wine aromas are identified

The aromas of wine are more diverse than its flavours. While the human tongue is limited to the five primary tastes, the wide array of fruit, earthy, leathery, floral, herbal, mineral, and woodsy flavours present in wine are derived from aroma notes sensed by the olfactory bulb.

Wine aromas are broadly categorised into three types: primary, secondary, and tertiary. Primary aromas are those specific to the grape variety itself. Secondary aromas are derived from the winemaking process, particularly the use of yeast for fermentation. Tertiary aromas, or the bouquet, arise during the ageing process, especially when the wine is aged in wooden barrels.

The process of wine tasting involves smelling the wine before taking a sip to identify some of its components. This is done by swirling the wine to release the aromas and then sniffing to detect them. The act of tasting wine involves inhaling the vaporized aroma compounds, which are then received by the olfactory receptors in the nasal cavity.

The diverse spectrum of aromas in wine is a result of the vine's adaptation to ecological conditions and competition among other plants. The volatile aroma compounds present in the skin and juice of a grape berry vary in composition according to the individual grape variety. These compounds are theorized to have developed as an evolutionary tool to aid in procreation by attracting insects and animals.

While the human nose can distinguish thousands of smells, naming them can be challenging. This phenomenon is known as the "tip of the nose phenomenon", and it can be countered by providing a list of possible choices to help with identification.

• Methoxypyrazine: grassy, herbaceous aroma found in Cabernet Sauvignon and Sauvignon Blanc.
• Monoterpenes: responsible for the floral aromatics of Gewürztraminer, Muscat, and Riesling, including geraniol, linalool, and nerol.
• Norisoprenoids: derived from carotenoids, these compounds include megastigmatrienone, which adds spice notes to Chardonnay, and zingerone, responsible for the spice notes in Syrah.
• Thiols/Mercaptans: sulphur-containing compounds that can produce an aroma of garlic and onion, considered a wine fault, but also contribute to varietal aromas.
• Esters: volatile flavour compounds created by the reaction of acids and alcohol in the wine, developing during fermentation and ageing. Examples include isoamyl acetate and ethyl acetate, which impart pear-drop candy or banana and pear flavours to young, white wines.
• Ketones and diketones: compounds like beta-ionone create the scent of violets in Pinot Noir or Syrah, while diacetyl adds a buttery or creamy note to Chardonnay.
• Lactones: formed in aged wines, such as sotolon, which is associated with Sauternes and imparts curry spice, nut, toast, or maple syrup aromas.
• Phenols: derived from oak ageing, with guaiacol adding smoky, toasty, and roasted aromas, and eugenol contributing clove notes.

The identification of wine aromas is a complex and fascinating process that involves the interaction of volatile compounds with our olfactory system.

The science behind wine aromas

Wine aromas are a complex and intriguing topic, and our understanding of them is constantly evolving. Wine contains a wide array of aromatic compounds, each contributing to its unique bouquet. While the exact number of aromas in a single wine is hard to pinpoint, it's estimated that there could be around 800-1000 aromatic compounds in wine. These compounds interact with each other and our senses to create the magical world of wine aromas that we know today.

The Basics of Wine Aromas

The sense of smell plays a crucial role in wine tasting and evaluation. Wine drinkers often smell the wine before tasting it, capturing aromatic compounds that volatilize from the glass. The human nose can detect a vast range of smells, and wine offers a unique sensory experience with its diverse aromas.

The Role of Grapes and Fermentation

The aromatic compounds in wine have various sources, including the grapes themselves. While grape juice doesn't smell exactly like wine, some aromatic compounds present in grapes survive fermentation and contribute to the final wine aroma. Additionally, during fermentation, yeasts create new aromatic compounds, further enhancing the wine's complexity.

The Impact of Ageing and Oak

As wine ages, its chemical composition evolves, leading to the development of new smells known as the wine's bouquet. Ageing in oak barrels can also impart unique aroma compounds, such as vanilla, caramel, or coconut notes. These compounds interact with the wine's natural constituents, creating a dynamic sensory experience.

Aroma Categories

Professional wine tasters often categorize wine aromas into primary, secondary, and tertiary aromas. Primary aromas are specific to the grape variety, while secondary aromas arise from the fermentation process. Tertiary aromas develop over time through bottle ageing or oak ageing, adding layers of depth and complexity to the wine.

The Science of Perception

It's important to understand that the perception of wine aromas is a highly individual experience. Each person has a unique set of olfactory receptors, resulting in different thresholds for detecting and recognizing aroma molecules. This variability in perception adds to the intrigue of wine aromas, as no two people may experience a wine's bouquet in the same way.

In conclusion, the science behind wine aromas is a multifaceted and captivating field. From the aromatic compounds in wine to the intricacies of perception, there is always more to discover and appreciate in the wonderful world of wine aromas.

The influence of oak and winemaking practices

The use of oak in winemaking dates back to ancient times, with the Greeks and Romans using oak barrels to transport and age their wines. Over the centuries, winemakers have refined the use of oak, and today, it remains an integral part of the winemaking tradition. Oak barrels are now a deliberate choice for many winemakers, adding flavour, aroma, and complexity to their wines.

Oak affects wine in several ways. Firstly, it adds flavour compounds, such as vanilla, clove, smoke, and coconut. These flavours elevate the wine's aromatic bouquet and taste. Secondly, oak allows for the slow intake of oxygen, which helps make the wine smoother and less astringent. This micro-oxygenation process contributes to the wine's aging and flavour development. Thirdly, oak provides the right environment for particular metabolic reactions, such as malolactic fermentation, which makes wines taste creamier.

The type of oak used in winemaking also makes a difference. The two most common types of oak barrels come from America and France, with Hungarian and Slavonian barrels also gaining popularity. American oak tends to have a bigger impact on a wine's flavour and aromatic elements, while French oak is considered the wine industry's gold standard, contributing more to the wine's overall palate presence.

The age of the oak barrel is another factor that influences the wine's characteristics. Newer barrels will have a more concentrated influence on the wine, as they lose some of their flavour-giving properties with each use. Winemakers who desire stronger oak flavours may opt for new barrels, while others may blend wine aged in new oak with wine aged in older barrels to achieve a balance of character and cost savings.

In addition to the type and age of oak, the way a barrel is dried and toasted will also impact the wine. A barrel's staves need to be dried in the open air before use, with longer maturation times resulting in more subtle characters. The cooper can then apply a heating process to control the 'toast' levels, which typically range from light to medium to dark. The greater the toast, the higher the oak's influence on the wine's colour, aroma, flavour, and overall style.

While oak barrels are the traditional method of imparting oak characteristics to wine, some winemakers may opt for alternative methods such as oak chips, which can be added at various stages of the winemaking process. Using oak chips can result in similar aromatic and quality characteristics as oak barrels at a lower cost. However, oak chips do not provide the same textural benefits as oak barrels.

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