When tasting wine, which element do you focus on most? Many of you might be conducting tastings that center more on aroma than on flavor. For winemakers, some of you may be paying more attention to the wine's compositional elements themselves, such as residual sugar and acidity levels.
One popular method in wine tasting is blind tasting. This approach involves exploring a wine's identity without any prior disclosure of information about the wine. In these tastings, alcohol content is often included as a subject of inquiry, along with origin, vintage, and grape varieties.
While there are various types of alcohol, most of what is contained in wine is ethanol. This ethanol ranks among the substances present in wine in large quantities. Consider a wine with 12% alcohol content: the amount of ethanol contained per liter is approximately 96 grams. This represents the second-highest content after water, which is the most abundant component in wine (excluding some exceptions like dessert wines). The amount of ethanol contained in wine far exceeds the residual sugar and acidity levels that are often of concern during tasting.
Could it be possible that alcohol, present in such substantial quantities, has no influence on wine tasting? Of course not. Alcohol affects wine's flavor both directly and indirectly.
This article examines how alcohol influences the sensory evaluation of wine and explores the reality of these effects.
Basic Knowledge of Alcohol
First, let's confirm the fundamental aspects of what alcohol contained in wine actually is.
In our daily lives, alcohol most commonly refers to alcoholic beverages—that is, liquor. Recently, the presence of disinfecting alcohol has also become part of our awareness. From a chemical perspective, however, alcohol refers to "a general term for compounds having a structure in which hydrogen in hydrocarbons is substituted with hydroxyl groups (-OH)." As this "general term" suggests, there are multiple types of alcohol: methanol, ethanol, propanol, ethylene glycol, glycerin, and so forth. These are further subdivided according to the number of hydroxyl groups they contain and their carbon count. Depending on such classifications, they may also be called by different names, such as higher alcohols.
Whether in wine and other alcoholic beverages or in hand sanitizing alcohol, the majority of the alcohol content is ethanol. Ethanol is classified into various categories—synthetic ethanol, fermented ethanol, industrial alcohol—based on its synthesis method and concentration. Different classifications fall under different government agencies and are subject to different related laws, but they are fundamentally the same compound.
Ethanol as a Component of Wine
Most wines have an alcohol content of around 12% or higher. The alcohol content at this level amounts to approximately 96 grams per liter. This quantity is second only to water and can rightfully be called a main component constituting wine.
Wine also contains small amounts of various higher alcohols, but the vast majority is ethanol (also called ethyl alcohol). The term "seishu," commonly heard in reference to sake, also refers to ethanol. The ethanol contained in wine and other alcoholic beverages is so-called fermented ethanol. It is produced as a metabolic byproduct by yeast during alcoholic fermentation. In the case of wine, this is often explained as "the sugar contained in grape juice being converted to alcohol."
This ethanol is a colorless, transparent, volatile liquid. As evidenced by its use for drinking, it has the characteristic of being relatively low in toxicity among alcohols. While the presence or absence of harm to the human body is a very important point when considering alcohol as a beverage, there is an equally important point for wine. That is the fact that it dissolves very well in water and can also dissolve a relatively wide variety of organic substances.
Wine contains an extremely large number of components. It is said that there are over 400 compounds directly related to wine's aroma alone. Not all of these components dissolve in water. There are compounds that have properties making them insoluble in water. This is where the presence of alcohol becomes very important—alcohol that can dissolve both water-soluble components and components that don't dissolve in water. It is precisely because wine contains ethanol that wine can exist as a liquid containing such complex components. Ethanol is truly a major element constituting wine.
Recognizing Alcohol as an Emulsifier
Alcohol serves the role of dissolving both water-soluble and less water-soluble components into wine. It can be said to function as a type of emulsifier.
The reason components that normally don't dissolve in water are dissolved in wine is because alcohol is present. Conversely, when alcohol disappears, such components can no longer remain dissolved in wine. And alcohol itself is a component that volatilizes easily. In other words, when alcohol volatilizes, some of the components that were dissolved in the wine accordingly become volatile as well.
The boiling point of ethanol is 79°C, but volatilization occurs at lower temperatures as well. Ethanol contained in alcoholic beverages slowly volatilizes even at room temperature. One reason why wine's aroma changes with temperature variations or changes in time after uncorking is this change in the solubility of aromatic compounds accompanying alcohol volatilization.
Why High-Alcohol Wines Feel "Heavy"
One wine comment that I feel is heard less frequently than before is "body." While I don't know the precise definition of the body expression, my impression is as follows: mainly for red wines, concentrated wines with high alcohol content are called "full-bodied," and as the degree of concentration becomes lighter, they are called "medium-bodied" or "light-bodied."
This body expression doesn't directly signify the level of alcohol content. However, as a result, wines that feel heavier in body tend to have higher alcohol content. This raises the question: "Do wines become concentrated because their alcohol content is high, or do they have high alcohol content because they are concentrated?" The answer is both.
While there are various detailed peripheral factors, roughly speaking, the so-called "concentration" depends on the amount of extractables contained in the wine. On the other hand, high alcohol content is fundamentally related to high sugar content in the must. Both are determined by the ripeness of grapes at harvest.
In highly ripe grapes, must sugar content increases while the amount of extractable components contained in the grapes also increases. Furthermore, in wines where must sugar content is high and alcohol content becomes elevated, extraction is more easily promoted. Additionally, in must with high sugar content, yeast metabolism becomes more easily activated, and the production of fermentation byproducts tends to increase. As a result, the amount of extractables contained in the finished wine tends to increase. Also, because solubility due to alcohol is maintained, more of the extracted components are retained in the wine. In other words, wines can become more concentrated and heavier.
Dissolution Isn't Always Beneficial
The presence of ethanol in wine allows more components to dissolve into the wine, making it more complex. This sounds like a very good thing. However, in reality, it's not necessarily all beneficial.
The fact that alcohol's intervention increases solubility and allows certain components to dissolve in wine also means that those components simultaneously lose volatility during that time. Even compounds with aroma cannot be perceived as fragrance by humans unless they volatilize. In other words, because they dissolve too well in wine, we cannot perceive the aromas that those components possess. The representative aroma suppressed by alcohol's presence is fruity aroma.
Aromas perceived as fruity have been verified to be most strongly felt in wine without alcohol content. This verification also reported the following: when alcohol content reaches 10%, the intensity of perceiving this aroma significantly decreases, and when it exceeds 14%, fruity character is almost imperceptible. This is considered to result from complex factors including not only the effect of alcohol increasing the solubility of volatile compounds with fruity aromas, but also the increase of factors that mask fruity aromas, such as more components dissolving into wine and the intensification of alcohol's own aroma.
Alcohol's Impact on Sensory Evaluation
Ethanol is a colorless, transparent liquid, but it is neither tasteless nor odorless. Ethanol itself possesses taste and aroma. Therefore, as its content increases, it more directly influences wine's taste and aroma.
When examining alcohol's function as an emulsifier, ethanol gives the impression of strongly influencing wine's aroma. However, when considering ethanol alone, the situation becomes quite different. Differences in alcohol content in wine influence taste more strongly than aroma.
It is almost established that ethanol has a complex taste possessing both bitterness and sweetness. It also has pain-stimulating properties that lead to a burning sensation in the throat. Recently, it has also been suggested that ethanol's fat solubility may allow it to pass through cell membranes of the tongue and taste cells, directly stimulating nerves themselves.
Alcohol has also been found to potentially affect taste perception directly and indirectly by acting on sensory organs. In beer and wine, there are many reports of cases where bitterness is emphasized. On the other hand, there are also reports that alcohol stimulates certain receptors, making perception of sweetness more sensitive and causing sweetness to be felt more strongly. Since there are also reports that perception of sweetness is conversely suppressed, it's difficult to say that alcohol necessarily emphasizes specific sensations. However, it is considered almost certain that alcohol influences perceptual interactions through receptor stimulation.
Incidentally, whether bitterness or sweetness is felt more strongly in response to alcohol appears to vary according to genes related to taste receptors possessed by the individual.
Alcohol Content Can No Longer Be Ignored in Wine Tasting
Current social trends are strongly inclining toward no-low and sober curious directions. Meanwhile, in winemaking, the alcohol content of finished wines tends to increase annually, driven by factors such as global warming due to climate change. According to one survey, wine alcohol content increased by an average of around 2% during the 20 years following the 1980s.
Contrary to consumer preferences, the following situation exists: in many countries and regions where wine laws are established, minimum alcohol content for wine is legally defined, while upper limits are often not specified. Furthermore, many methods for reducing alcohol content in wine are restricted from the standpoint of certification regulations by various organizations. For these reasons, alcohol content tends to increase in order to sell and distribute wine as "wine."
Rising alcohol content becomes a direct and indirect factor that changes the taste and aroma perceived in wine. Moreover, the scope of this influence doesn't remain small. Now that rising alcohol content listed on labels compared to vintages from several years ago is frequently confirmed, it's no longer possible to ignore alcohol content during wine tasting.
In vertical tastings, where the same producer's same wine is tasted across multiple vintages, differences in flavor are often explained by climatic differences of each vintage. While differences in blending or winemaking methods may be added to this, the alcohol content at the time of production and at the time of consumption may not often be considered. Certainly, climatic differences indirectly signify grape ripeness at harvest. However, strictly speaking, the two are not equivalent, and differences in taste and aroma derived from alcohol content cannot be explained by climate alone.
Not limited to vertical tastings, when you drink a recent vintage and feel that the taste and aroma are different from when you drank it before, it might be good to focus on alcohol content and consider that as a reason.
