The traditional art of carbonic maceration in winemaking

The concept of carbonic maceration, a traditional winemaking technique, dates back to a scientific reference in 1872 by the French chemist Louis Pasteur. However, it was not until the mid-20th century that French researchers Michel Flanzy and his son Claude Flanzy extensively studied and published works on this method, earning them recognition as the pioneers of modern carbonic maceration.

Historically in Spain, particularly in the regions of Rioja Alta and Rioja Alavesa, carbonic maceration has been a longstanding practice, predominantly with the Tempranillo grape. Until the late 18th century, it was the sole winemaking method in these areas before the introduction of French techniques.

Carbonic maceration is a "spontaneous" winemaking process, meaning it does not involve adding external yeast for alcoholic fermentation. Instead, it relies solely on native yeasts from the grapes and vineyard. This method may have been traditionally used in various regions unknowingly.

In France, carbonic maceration also has a traditional background, especially in the production of Beaujolais wines made from the Gamay grape.

Process of carbonic maceration

The process of carbonic maceration occurs in two distinct stages, although they often overlap in practice.

The initial phase, lasting one to two weeks, occurs intracellularly. Freshly harvested grape clusters, including the stems, are placed in tanks under a carbon dioxide-rich atmosphere, displacing oxygen. This anaerobic environment is crucial for the process.

During the second stage, the must continues its alcoholic fermentation without the solid parts.

For intracellular fermentation, small to medium-sized containers (up to 300 liters) are preferred to keep the grape clusters intact and to facilitate later separation of the must from solids. Larger tanks require techniques to prevent cluster breakage.

Carbon dioxide is introduced either through industrial gas or by initiating a small alcoholic fermentation at the bottom of the container, which naturally releases carbon dioxide, displacing any oxygen. Both methods yield the same final wine quality.

A unique aspect of carbonic maceration is that tanks must be filled completely as there is no volume increase, rather a decrease. This method also requires significant heat, between 30º and 32ºC, necessitating strict temperature control.

During carbonic maceration, there is a risk of harmful bacterial proliferation, making an initial sulfite addition advisable to maintain hygienic conditions.

Generally, carbonic maceration undergoes no manipulation. However, some winemakers perform pump-overs to enhance extraction, risking the incorporation of herbaceous flavors or green tannins. Stirring or punching down is not recommended due to the significant breakage of grapes it can cause.

An auto-crushing phenomenon occurs during carbonic maceration as the weight and time degrade the berries, leading to a gradual crushing that transitions from the first to the second phase, where alcoholic fermentation of the must begins.

After the initial phase, the pre-fermented must is extracted through two methods: about 70% from 'bleeding' or juice collected at the tank's bottom and the remainder from pressing the solids. Traditionally, these were done simultaneously through manual crushing and slow extraction.

Finally, the resulting must, free from solids, undergoes the usual alcoholic fermentation. This step is delicate, requiring additional sulfiting and careful monitoring to avoid temperature fluctuations and fermentation halts, which could spoil the wine.

Characteristics of carbonic maceration wines

Wines produced through carbonic maceration are distinctive. They are lighter, less acidic, and have less sugar compared to conventionally produced wines.

Despite their intense violet color, these wines are low in polyphenols. They are notable for their significantly higher aromatic intensity, with purely fruity aromas, and have a smooth and pleasant palate. Typically, these wines are consumed young.

While primarily used for red wines, carbonic maceration can also be applied to rosé and white wines, albeit for a shorter duration of 2 to 3 days.