The Unique Winemaking Behind Rioja’s Carbonic Maceration Wines

While sounding somewhat technical to non-wine professionals, carbonic maceration and semi-carbonic maceration are common forms of whole-bunch fermentation used by winemakers the world over.

With standard alcoholic fermentation in red wines, grapes are crushed to release their juice, and yeasts then convert the juice’s sugar into alcohol through aerobic respiration in the presence of the skins.  However, the goal of whole bunch fermentation as Cvne’s winemaker María Larrea explained, is to create an oxygen-free environment for the uncrushed fruit.  This lack of oxygen forces the grapes to change from aerobic respiration to anaerobic metabolism.  In the anaerobic process, some of the sugar in the grapes is converted to alcohol without the aid of any yeast and is referred to as intracellular fermentation, which takes place inside the grape. 

Intracellular fermentation has several outcomes.  Firstly, malic acid within the grape is broken down to create ethanol, which lowers the overall acidity in the finished wine.  Glycerol levels increase, which brings a softer mouthfeel to the wine.  Color compounds move from the skin to the pulp, turning their flesh pink and causing the vibrant colors in the resulting wine.  Finally, a range of distinctive flavors are created, the aforementioned notes of banana, strawberry gum, cinnamon and kirsch.

While unique, the fermentation is short lived, as the grapes only produce around 2% abv before splitting open and releasing some of their juice.  The skins are then pressed, and the juice finishes alcoholic fermentation off the skins, with the goal being to extract very little tannin and produce a softer wine that is easy to drink young. 

The wine’s easy drinkability along with its overtly fruity and somewhat candied flavors has typically deprived it of greater recognition.  Make no mistake however, the winemaking behind it is anything but simple, and while different approaches are taken at wineries like Cune, Bodegas Palacio, and Remírez de Ganuza, what’s clear is that these wines receive just as much oenological attention as their more “serious” siblings.

Carbonic maceration versus semi-carbonic maceration

Although we associate the young wines of Rioja Alavesa with carbonic maceration, winemaker Roberto Rodríguez of Bodegas Palacio explained that until CO2 gas could be added artificially to flush out fermentation vats, in reality these wines were produced via semi-carbonic maceration, the way Milflores Tempranillo is made today. 

With semi-carbonic maceration, the CO2 needed to displace the oxygen is produced naturally when the whole bunches at the bottom of the vat are crushed by the weight of those bunches above them.  The juice released at the bottom of the vat starts to ferment, producing CO2 in the process and blanketing the bunches above them, allowing intracellular fermentation to take place in the berries that remain intact. 

When making Milflores, Rodriguez also destems all of the grape bunches but does so carefully enough that only around half the berries have their skins broken.  These are placed at the bottom of the vat.  Those berries on top are left intact, and thus undergo intracellular fermentation.  This results in a different style of wine in which the carbonic flavors are slightly less pronounced, and any green tannin that might have been absorbed from the stems is avoided.

At Remírez de Ganuza however, winemaker Jesús Mendoza’s goal when making Erre Punto is to create the purest carbonic maceration wine possible.  He stressed the importance of using smaller (i.e. shorter and wider) fermentation vats.  These serve to take the pressure off the berries at the bottom, leaving them mostly intact and thus allowing the overwhelming majority to undergo intracellular fermentation, which creates more pronounced carbonic flavors in the process.  María Larrea uses a similar approach at Cune. 

Perhaps the most unique part of producing Erre Punto however is the use of 60-year-old Tempranillo vines.  While the riper “shoulders” of each bunch go into the flagship Reserva, the tips are cut off and used to make Erre Punto.    

Given the lower price points of carbonic maceration wines, and the lower yields of old vines, it might seem hard to justify such an expense.  Mendoza explained however that the greater concentration brought by older vines is reflected in the final wine, giving them a point of difference in the marketplace.  At the same time, the use of the tips, which are less exposed to the sun and have therefore retained more acidity, contributes a greater sense of freshness to Erre Punto, aided further by a co-fermentation with white grapes such as Viura and Malvasia. 

So, the next time you’re enjoying a newly released young wine from Rioja, take a second to remember the unique processes behind it

.Text: Nygil Murrel