These days, more of us in Australia are drinking softer/lighter reds.
The term carbonic maceration is often associated with these styles of wines and rolls off us wine biz people's tongues (I am very guilty here) assuming everyone knows what we are talking about! You may have heard this term mostly when delving into the wines of Beaujolais in France. It is also employed north of Rioja in Spain to produce the young reds called Joven. My aim here is to demystify this technical term.
Carbonic maceration is a process that leads to fermentation which involves whole bunches of grapes that have intact, uncrushed or unruptured berries and that takes place in an oxygen-free environment that's made that way by carbon dioxide gas. The old term for CO2 was carbonic gas, so this is where it takes its name. Unlike conventional fermentation, this process does not involve yeast munching up the sugars in the grapes to produce alcohol. The winemaker will decide on what portion of the harvest he wants to undergo this process.
The process has two major variations:
Semi-Carbonic Maceration - The older process of the two but funnily enough, the most commonly used. The winemaker will fill a container/vat with intact whole, uncrushed grapes. The deeper the vessel, the greater the proportion of grapes that could be exposed to an anaerobic environment caused by the release of carbon dioxide from the crushed grapes on the bottom. CO2 is denser and heavier than oxygen and as it fills the vessel, it pushes the oxygen out the gap between the lid and the vessel or out an airlock. A different kind of fermentation takes place here called intracellular fermentation. The grapes absorb the carbon dioxide and start a yeast and oxygen free fermentation. This lowers the acidity of the juice and the tannins move into the grape's pulp (therefore producing a less tannic wine than conventional extraction) turning it a pinky/purple colour and flavours of raspberry, strawberry, cherry and even banana. The process shuts itself down when the alcohol levels reach around 2.5%. The juice/wine will then have to undergo a second but conventional fermentation to produce a conventional wine, hence the term semi-carbonic. So, the resulting wine is less tannic, less acidic and will have brighter, fresher red fruits.
Carbonic Maceration - The winemaker will fill the vessel with carbon dioxide, chasing out all the oxygen and then adds the whole grapes very carefully so as not to crush and release any juice. From here, it follows the same process as semi-carbonic maceration. However, the resulting wines are light in colour and even less tannic.