Maceration is one of the winemaking techniques used in wine production. In Japan, this technique is also called "kamoshi" (醸し), and it refers to the process of soaking grape skins and seeds in grape juice or wine for periods ranging from several hours to several days, or in some cases, several months.
Techniques called "skin contact" or "skin maceration" are essentially different names for the same maceration process.
While maceration goes by various names, its purpose can be broadly described as "extraction." The goal of maceration is to draw out various components contained in grape skins and seeds into the grape juice or wine, thereby changing the wine's flavor and aroma.
Maceration comes in several types depending on the method and timing employed. Today, we will examine one of these types—Extended Maceration (EM)—and the tannins that this technique primarily extracts.
Types of Maceration and Their Differences
Maceration can be broadly divided into three types: regular maceration, extended maceration (EM), and carbonic maceration.
These three types of maceration are distinguished by when they are performed. Regular maceration and carbonic maceration are conducted before fermentation, while EM is performed after fermentation. Regular maceration and carbonic maceration are differentiated by whether grape skins and seeds are soaked in pre-fermentation grape juice or in a carbon dioxide gas environment.
When people generally refer to maceration, they mean regular maceration performed before fermentation. When regular maceration is conducted in a low-temperature environment, it is sometimes called "cold maceration" or "cold soak" to distinguish it from maceration performed at other temperatures.
EM involves leaving the skins and seeds in the wine-containing vessel even after fermentation has completed.
The Actual Process of EM
The EM process becomes relatively easy to understand when we consider red wine production. In red wine production, grapes are not pressed to extract the red color. Instead, they are lightly crushed to allow the juice to emerge, and both skins and seeds are placed together in the vessel in this crushed state. The grape juice ferments in this condition, and after fermentation is complete, the mixture is put into a press and squeezed to separate the liquid that has become wine from the skins and seeds. In EM, the period between the end of fermentation and pressing is extended, allowing further extraction to continue during this time.
What Each Type of Maceration Extracts
All maceration techniques, including carbonic maceration which holds a somewhat special position among winemaking techniques, share essentially the same purpose: to extract aromatic compounds and components called phenols from grape skins or seeds.
So why bother dividing the methods? The difference lies in the state of the liquid in which the grape skins and seeds are soaked.
In regular maceration and carbonic maceration, the skins and seeds come into contact with pre-fermentation grape juice. Therefore, at this stage, primarily water-soluble components are extracted.
In contrast, with EM, the skins and seeds are soaked in post-fermentation wine—that is, in alcohol. This allows for the extraction not only of water-soluble components but also of components that are poorly soluble in water but readily soluble in alcohol.
Anthocyanins, which provide red wine's color, and some aromatic compounds that contribute to wine's fragrance are water-soluble, so they can be adequately extracted through regular maceration or carbonic maceration. However, when the goal is to extract more phenols that are poorly soluble in water but readily soluble in alcohol, extraction through EM, where the solvent contains alcohol, becomes necessary.
The prime example of phenols that are poorly soluble in water but readily soluble in alcohol is tannins, a type of polyphenol.
Tannins are a Type of Plant Polyphenol
Tannins, which EM aims to extract. While this is a term we hear very frequently in wine-related discussions, many people may not have a clear understanding of what tannins actually are.
Tannin is a collective term for certain types of phenolic compounds and does not refer to any specific substance. The name derives from its historical use in leather tanning. According to historical records, tannins were already documented in Egyptian texts believed to have been written around 1850 BCE, making them compounds that have been familiar to humanity for an extremely long time.
These tannins are, in fact, plant-derived polyphenols.
Polyphenols are compounds composed of multiple phenolic components linked together. To use an analogy, if a single Lego block represents a phenol, then polyphenols would be several Lego blocks of different colors and shapes connected together, and tannins would be those assembled according to certain specific patterns.
Just as Lego blocks can be combined in countless ways, there are many types of tannins. Among these, tannins are classified according to their properties as follows:
Classification of Tannins
Hydrolyzable Tannins
- Gallotannins
- Ellagitannins
- Others
Condensed (Non-hydrolyzable) Tannins
- Simple condensed tannins
- Complex condensed tannins
- Other tannins
To elaborate slightly, hydrolyzable tannins are compounds where polyhydric phenolic acids such as gallic acid are ester-bonded to polyhydric alcohols such as sugars with multiple hydroxyl groups. Condensed tannins are compounds where multiple flavonoids are linked by carbon-carbon single bonds. It is known that condensed tannins often have the additional feature of gallic acid ester-bonded to the basic structure mentioned above.
Among condensed tannins, simple condensed tannins are also called proanthocyanidins. Proanthocyanidin means "a compound that serves as the precursor to anthocyanidin, which produces red pigments."
The central flavonoids in condensed tannins are mainly flavan-3-ols, with (−)-epicatechin, (+)-catechin, (−)-epigallocatechin, and (+)-gallocatechin being the most abundant. It should be noted that unless aged in wooden barrels or subjected to certain special treatments, wines contain only condensed tannins.
Just as tannins were originally used for leather tanning, they have a property of readily binding with proteins and metal ions, and this leads to another characteristic: astringency.
Tannins Possess Both Bitterness and Astringency
Those who have experienced eating astringent persimmons will know that consuming them creates a sensation of astringency—as if all the moisture in your mouth has been suddenly absorbed. This is caused by a component called persimmon tannin, which is actually a type of tannin called kaki-tannin.
This astringent sensation occurs because tannins' tendency to bind readily with proteins causes them to bind with and remove the protective layer that mucin, a protein in saliva, forms on the inside of the mouth.
Tannins are characterized by both bitterness and astringency. However, while bitterness is a taste, astringency is not. In other words, bitterness, being a taste, is detected by taste buds on the tongue, but the perception of astringency, which is not a taste, does not involve taste buds. This is why the perception of astringency involves tannins' characteristic tendency to bind readily with proteins.
The Effect of Tannin Polymerization Degree on Taste Perception
The astringency and bitterness that tannins possess are said to change according to the degree of polymerization of the tannins.
The degree of polymerization refers to the number of connected Lego blocks mentioned earlier. Tannins with fewer connected blocks are called low-polymerization-degree tannins, while those with many blocks connected are called high-polymerization-degree tannins.
Generally, lower polymerization degrees increase bitterness, while higher polymerization degrees increase astringency. This is because high-polymerization-degree tannins exceed the size of taste buds on the tongue, making them difficult to perceive as taste.
When the polymerization degree exceeds a certain range, the size difference between the tannin and proteins becomes too large for binding to occur, and the tannin no longer exhibits astringency. As the polymerization degree increases further, the tannin can no longer remain dissolved in the wine and precipitates as crystals.
Tannin Polymerization Degree and Wine Flavor
The bitterness or astringency that tannins possess is influenced by both the polymerization degree of the tannins and their concentration. Higher concentrations of high-polymerization-degree tannins make wine more astringent, while wines containing more low-polymerization-degree tannins become more bitter.
Tannins contained in grape skins generally have high polymerization degrees, while tannins contained in seeds have low polymerization degrees.
This becomes very understandable when we consider grapes' characteristics as plants.
Grape Survival Strategy and Tannins
Grapes need birds and animals to eat their fruit and then spread their seeds through subsequent excretion. While the skin and flesh need to be palatable to attract birds and animals, it would be problematic if the seeds that need to be dispersed were also chewed up.
The solution is to make the seeds bitter and unpalatable.
The cause of this seed bitterness is tannins.
Bitter tannins are low-polymerization-degree tannins. In other words, tannins contained in seeds need to have low polymerization degrees as part of grapes' survival strategy. Grape seeds contain higher amounts of condensed tannins.
Wine Aging and Tannin Changes
When expressing how long wine can maintain its flavor and aroma, the term "aging potential" is often used. The amount of phenols contained in wine greatly influences this aging potential.
Phenols have strong antioxidant properties and readily bind with oxygen when wine comes into contact with it, preventing other components related to wine's flavor and aroma from being affected by oxygen. Through this binding with oxygen, the polymerization degree of phenols gradually increases, and they eventually precipitate and accumulate as sediment at the bottom of the bottle. Tannins, being a type of polyphenol, behave in the same way.
Due to these phenolic changes occurring in wine, it is often said that aged wines develop more mellow astringency.
This is not incorrect. It has been verified and confirmed that the total amount of phenols decreases in aged bottles.
However, when we focus specifically on tannins, the situation becomes somewhat more complex. It is believed that tannins behave differently during aging depending on their type.
Types of Tannins and Their Changes in Wine
Tannins can be broadly divided into hydrolyzable tannins and condensed tannins.
Incidentally, regardless of type, tannins with more gallic acid bonds are said to produce stronger astringency. This appears to be a factor separate from polymerization degree, and when tannins have the same polymerization degree but different numbers of gallic acid bonds, those with more gallic acid bonds reportedly feel more astringent.
On the other hand, there is a factor that affects tannins regardless of such structural considerations: acid.
Tannin Changes Due to Acid
Hydrolyzable tannins are hydrolyzed by acid to become polyalcohols and phenolic carboxylic acids. In other words, this type of tannin reduces its polymerization degree through reaction with acid.
In contrast, condensed tannins, especially simple condensed tannins also called proanthocyanidins, do not undergo hydrolysis of their basic structure. Instead, acid causes further polymerization, forming phlobaphenes that are poorly soluble in water. Phlobaphenes possess bitterness but not astringency.
In other words, as tannins age, they lose astringency—in one case through reduced polymerization degree, and in the other through increased polymerization degree. Simultaneously, acid is consumed in the reaction, reducing its quantity and decreasing the wine's acidity.
This is why aging makes wine's acidity more rounded, reduces tannin-derived astringency, and creates a "silky mouthfeel."
Extended Maceration and Wine Aging Potential
Having examined tannin characteristics up to this point, let us return to EM.
EM extracts more phenols that are readily soluble in alcohol. In other words, wines subjected to EM have increased tannin content.
Tannin content is overwhelmingly higher in seeds compared to skins or juice. Therefore, most tannins extracted through EM derive from seeds. Tannins contained in grape seeds are low-polymerization-degree condensed tannins that simultaneously feature high numbers of gallic acid bonds.
In other words, tannins extracted through EM possess both bitterness and strong astringency.
The more tannins extracted through EM, the longer it takes for their astringency to fade through binding with acid. If we define a wine's aging potential as the time it takes for astringency to fade, then wines with higher amounts of tannin extracted through EM can be said to have greater aging potential.
Summary | Can EM Become Wine's Character?
Whether regular maceration or EM, excessive extraction of phenolic compounds makes the individuality that grapes possess less visible. At minimum, the characteristics of terroir and vineyard become diluted.
On the other hand, if we consider that this is merely extracting the phenols originally contained in the grapes, we could argue that wines subjected to thorough extraction are those that truly express the original character of the grapes used as raw material. How this is perceived and which direction to take depends entirely on the winemaker's philosophy.
Among the various types of maceration, EM has the disadvantage of color reduction due to anthocyanin re-adsorption, but it is an extremely effective means of enhancing wine's aging potential. It is probably an essential technique for achieving remarkably long aging periods. However, the trade-off is the impact on wine flavor.
Challenges and Possibilities of EM
The condensed tannins extracted through EM may react with acid to form phlobaphenes, and when these phlobaphenes precipitate, both astringency and bitterness may eventually become less perceptible. However, this requires an extremely long time, and during this period, drinkers will experience the unpleasant sensations that tannins bring.
While these aspects might also be considered part of wine's character, we need to consider whether that aging time truly has meaning and whether the magnitude of the trade-off really balances out.
Given this, when performing EM, adjusting its degree becomes essential.
Your Trusted Partner in Winemaking
Are you looking to resolve day-to-day questions and uncertainties in viticulture or winemaking? Hoping to take your wine quality to the next level? We're here to help.
At Nagi Wines, we support every step of your winemaking process—from vine to barrel to bottle. Our seasoned experts provide on-site, hands-on guidance to enhance your knowledge, refine your technique, and elevate the overall quality of your wines.
If you're seeking professional support while keeping costs under control, don’t hesitate to get in touch. Let's craft excellence together.
