In a nutshell, grapes are fruits, and all fruits have unique aromatic profiles. These profiles are different across different species and change as the fruit ripens. For example, the smell of a Granny Smith apple is much different than that of a Fuji apple, but they are both still apples. Wine grapes (Vitis vinifera) are similar in this way and express very complex aromatic profiles, especially after they have been fermented and turned into wine. Many of the aromas come from the grapes themselves, but there are aromatic compounds found in wine that can come from external influences and not the grape itself.
Here is where we dive into the science, organic chemistry to be precise! Fermentation is the key to all of these aromatics and explains why wine has more complexity than your typical apple. Fermentation unlocks the aromatic molecules from the sugars in the grapes, and when those sugars are turned into alcohol, via the natural fermentation process, the aromatic compounds are released and can be detected by smell. Our brains can break down these complex aromas depending on the concentration of the compound in the given wine, personal sensitivity to smell, and practice.
Here is a list of a few aromatic compounds that can be found in wine and how they contribute to what you smell in the glass:
Esters: Occur due to the mixing of acids and alcohols. They are the key compound in the expression of primary fruit flavors in young wines. They are one of the first compounds you will smell as they are very light in molecular weight and become airborne at the swish of a glass.
Aldehydes: Can come from both the grape itself and from the influence of oak aging. When coming from the grape, they can smell of fresh grass and tomato leaf (Sauvignon Blanc). When coming from oak influence, aldehydes can smell of vanilla bean.
Pyrazines: Can naturally occur in grapes and can also come from stems and seeds. They smell herbaceous, specifically, they can smell like green bell pepper at times. The presence of this compound can also occur in wine made from grapes that were picked before reaching peak ripeness.
Diacetyl: A specific diketone compound that smells of melted butter and can suggest the palate will have a creamy texture to it. Diacetyl is a byproduct of malolactic fermentation where bacteria transforms sharp malic acid in wine into much softer lactic acid. This is commonly found in oaked California Chardonnays and smells of buttered popcorn.
Terpens: Found primarily in the skins of grapes that contributes floral and citrus notes in wines. These compounds are also found in abundance in nature (flowers, fruits, and leaves of many plants).
Lactones: Formed in wines that have aged or have seen significant oak aging. It can smell of dried fruits, nuts, toast or maple syrup in older wines, and coconut in heavily oaked wines.
Phenols: Derived from oak aging. One set of possible aromatics includes smoky, toasty and roasted aromas, while another set includes spicy notes, particularly of clove.
If you have made it to this point of the blog you deserve both a gold medal and a glass of champagne, which we certainly carry at the shop. Our educational content is developed in-house and is intended to enhance your personal wine journey. If you ever have any questions feel free to reach out to our expert team of sommeliers.