The Winemaking Technique of Carbonic Maceration

Wine terminology related to production processes is often difficult to understand and unfamiliar due to the extensive borrowing from French. However, among such terms, "carbonic maceration" is a name that many people may have heard of at some point.

Carbonic maceration is a winemaking technique widely known as the production method for "Beaujolais Nouveau," a wine that enjoys particularly high recognition in Japan alongside Champagne.

In Japan, it is commonly called "carbonic maceration" as a translation from English, but in French, it is "Macération carbonique" (maceration carbonique) with the word order reversed. This is simply a difference in nomenclature due to language differences, so neither is more correct than the other. However, the author is more familiar with the French version, and it seems that this is more commonly used in specialized literature and similar sources.

This technique already seems confusing just because there are multiple ways to refer to it, and despite its high recognition, it is actually one of the winemaking methods whose content is not properly understood.

This article will explain Macération carbonique.

What is Macération carbonique?

First, let me clarify that this technique called Macération carbonique is often thought of as:

• A technique used only for red wines
• A winemaking method specifically for Beaujolais Nouveau

However, both of these assumptions are incorrect.

While it is true that this technique is rarely used for white wines due to its nature, it is not impossible to apply it to them. Additionally, while Beaujolais Nouveau is famous as a wine made using this method, it is not a dedicated winemaking technique exclusively for this wine.

Although it falls into a somewhat specialized category, this is one of the general winemaking techniques. As a technology, it was first proposed in 1935 and began to be utilized in the 1960s, so it is not particularly new.

The details of the winemaking technique will be explained below, but as an overview, the Japanese translation "carbon dioxide impregnation method" surprisingly captures the essence of the content succinctly and is easy to understand.

Macération carbonique is a technique that promotes extraction from grape skins and the decomposition of some organic acids "within the fruit" by placing grapes in a carbon dioxide (CO2) atmosphere.

A Technique for Creating Fruity Wines with Low Tannins

Wines made using Macération carbonique have the following characteristics:

• Low tannins and fruity character
• Suitable for early consumption
• Not suitable for long-term aging

Translating this into more technical winemaking language:

• Easy to drink with little astringency or bitterness due to low tannin content
• Mild acidity similar to long-aged wines due to the decomposition of some organic acids
• Made in what could be considered an already aged state
• Not suitable for aging due to low phenolic and acid content

This perfectly represents the characteristics of this winemaking technique.

Let's examine what this means in detail.

Reactions by "Enzymes," Not "Yeast"

Macération carbonique is sometimes explained using the term fermentation, which may lead to understanding it as "fermentation = reactions by yeast."

However, in reality, the Macération carbonique process is triggered and executed by enzymatic reactions that exist within the grape fruit itself, with no yeast involvement whatsoever.

On the other hand, Macération carbonique can be implemented in parallel with normal maceration fermentation as a variation during execution. Since fermentation yeast also exists simultaneously in this case, it is very easy to confuse the two, but it is necessary to understand them as clearly distinct techniques.

Anaerobic Environment for "Inward-Directed" Enzymatic Reactions

One of the important conditions in Macération carbonique is placing grape fruit in a carbon dioxide atmosphere. The allowable oxygen concentration in the atmosphere at this time is 1% or less.

When we think of eliminating oxygen as much as possible to create a primarily carbon dioxide atmosphere, we tend to imagine a pressurized environment, but in Macération carbonique, this condition is not for pressurization purposes. The goal is to direct the enzyme activity inward.

When enzymes are activated, oxygen is required in most cases. However, when oxygen is removed from the external atmosphere, enzymes try to gain activity using the trace amounts of oxygen present within the grape berries. In other words, the enzyme activity is reversed from outward-directed to inward-directed.

As a result, enzymatic reactions that are completed within the grape cell walls occur. This reaction is exactly what Macération carbonique aims to achieve.

Enzymatic Decomposition of Malic Acid

The most significant enzymatic reaction that occurs during Macération carbonique is the decomposition of malic acid.

When discussing malic acid decomposition, MLF (Malo-Lactic Fermentation) using lactic acid bacteria is well known. However, the major difference is that in the enzymatic reactions of Macération carbonique, the decomposition of malic acid does not produce lactic acid.

Instead, this reaction produces ethanol, or alcohol, at a maximum of approximately 2.5% vol.

Note As an aside, the fact that alcohol is produced is likely one of the reasons why Macération carbonique is explained using the term "fermentation."

The amount of malic acid decomposed by enzymatic reactions in Macération carbonique varies depending on environmental temperature and grape variety, but reports show it can reach up to 57% of the original content.

While ethanol is produced during this acid decomposition process as already mentioned, small amounts of glycerin, succinic acid, shikimic acid, and formic acid are also known to be produced. Additionally, pectin decomposition occurs in parallel with this malic acid decomposition, and the associated production of methanol is also one of the characteristics of this technique.

Pigment Extraction into the Pulp

Another characteristic of Macération carbonique is the extraction of pigments, namely Anthocyanins.

Normally, anthocyanin extraction refers to the migration from grape skins to the juice existing "outside" the skins. However, in Macération carbonique, the extraction is directed "inward" from the skins.

The pulp of grape berries that have undergone Macération carbonique is stained an extremely deep red color by anthocyanins extracted from the skins. By pressing this red-stained pulp after the process is complete, deeply colored and vibrant juice can be obtained.

The efficiency of this "inward-directed extraction" is extremely high. The color intensity of juice obtained by pressing fruit that has undergone Macération carbonique is approximately twice as concentrated as that from normal maceration fermentation, though this varies by grape variety.

It should be noted that Macération carbonique is not a comprehensive winemaking technique that completes wine production by itself. Rather, it is one variation of the maceration process that occurs between grape harvest and pressing or fermentation.

In other words, strictly speaking, normal alcoholic fermentation is required after Macération carbonique.

Why Are Tannins Low and Astringency Absent?

The major reason why wines made using this technique remain low in tannin content is that the Macération carbonique environment creates conditions where tannins are difficult to extract.

Let me explain in more detail. The key points to understand are these two:

• While anthocyanins, which contribute to color, are mostly present in grape skins, tannins are predominantly found in seeds
• Tannins are primarily soluble in alcohol

Grape fruit during the Macération carbonique process is generally in an uncrushed state. Therefore, naturally, the seeds are not in contact with the juice in the same way as normal "maceration."

Additionally, the alcohol concentration during Macération carbonique remains at an average of about 2% vol. even at the end of the reaction.

Since the seeds, which are the source of tannins, are not actively in contact with the juice, and even when they are in contact, the alcohol content is only about 2% vol., virtually no tannins are extracted due to these two factors.

The subsequent alcoholic fermentation is carried out with the juice separated from the skins and seeds after pressing. Therefore, the seeds again have no opportunity to contact alcohol, and tannins are not extracted. As a result, wines with little astringency from tannins and white wine-like fruitiness are produced.

Methods of Macération carbonique

There are several variations in the methods of conducting Macération carbonique. This variety of approaches seems to be one of the major obstacles to understanding this technique.

First, the prerequisites for conducting Macération carbonique are as follows:

• Use only 100% healthy fruit
• Grape berries in the process container must remain uncrushed
• A carbon dioxide atmosphere must be established

However, when considering actual operations, it becomes clear that meeting all these conditions is quite difficult. In particular, achieving "2. maintaining grapes in an uncrushed state" is nearly impossible. This is because fruit inevitably gets crushed due to its own weight and dropping during container loading.

Multiple variations have been conceived and implemented, starting from the question of how to handle the juice that emerges from these crushed grapes.

The Strictly Principled Method

The first variation is a method that completes this process while strictly adhering to the principles of Macération carbonique.

In this variation, after placing grapes in the container, the juice that has emerged is removed from the container once. The Macération carbonique process is then completed with absolutely no juice present around the fruit. After pressing, the previously removed juice is returned to the pressed juice for alcoholic fermentation.

While this is certainly a method that follows the fundamental principles of Macération carbonique, it requires significant labor and increases various risks including microbial contamination. Furthermore, it is costly and could be considered an inefficient method.

Additionally, this method requires that all carbon dioxide gas needed for Macération carbonique be supplied from external sources.

The Method Parallel to Normal Maceration Fermentation

This is a more practical approach.

The juice that emerges when grapes are placed in the container is treated by adding yeast and proceeding to the alcoholic fermentation process. Simultaneously, Macération carbonique is conducted within the uncrushed fruit in the upper part of the container, running these two states in parallel.

Whether to limit the fermentation portion to only the juice naturally produced by grape crushing in the container, or to add some pre-crushed fruit, varies according to each winery's philosophy.

In either case, fermentation by wild yeast risks compromising the characteristics that can be obtained through Macération carbonique, so dried yeast is commonly added. The fact that the fermentation environment remains under a carbon dioxide atmosphere throughout is also a major reason for using cultured yeast.

In this method, it is desirable to initially fill the container with externally supplied carbon dioxide gas at the beginning of the process. However, thereafter, it can be maintained by the carbon dioxide produced through fermentation.

It bears repeating that this process of "adding yeast" is solely for the alcoholic fermentation process that runs parallel to Macération carbonique. Therefore, please note that it is completely unrelated to the Macération carbonique process itself.

Summary

Macération carbonique is originally conducted with no external contact between fruit and juice. However, in actual winemaking operations, it is commonly performed in parallel with normal maceration and alcoholic fermentation.

When combined with multiple techniques like this, various complex influences arise. As a result, wines that are purely influenced only by Macération carbonique are actually not very common.

Additionally, this intertwined parallel implementation of multiple techniques makes it difficult to understand what this process actually entails when viewed from the outside. There are even assertions that treat everything combined as Macération carbonique.

This winemaking technique tends to be recognized primarily by name, influenced by Beaujolais Nouveau. By properly understanding its content, you can understand the intentions behind wines made using this technique and whether they are successful.

While it is a labor-intensive and costly technique, understanding why wineries deliberately choose to use it may change how you perceive the taste of the wine.

We have also published an article that summarizes only the essential points from this article to provide an even simpler explanation of Macération carbonique. If you still don't quite understand this winemaking method, please take a look.

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