1- Aging in oak barrels
Aging is a long and delicate process that seeks to confer a series of sensory characters to a wine in order to increase its complexity in the mouth and increase its stability.
Traditionally, this process takes place inside wooden barrels of different forest species (American oak, French oak, chestnut, etc.), and in this stage there is a natural modification of the chemical composition of the wine as a consequence of the contact of this with the wood from the barrel.
During this process, a release of tannins, phenolic acids and volatile compounds of the wood is generated that modify its sensory characteristics (Garde-Cerdán and Ancín-Azpilicueta, 2006).
In addition, a stabilization of the wine coloring matter is generated due to the micro-oxygenation process, which produces an increase in the quality of the final wine (Nguyen et al., 2010).
2- Use of chips in winemaking
Given the high cost and time required for this process, in recent years the use of wood chips in winemaking has been proposed as an alternative , of different sizes (powder, shavings, chips and planks) for the production of wines (Figure 1 ), in order to transmit characteristics of wood quickly and economically, under the premise that this process generates a product similar to that produced according to the traditional system (Araptisas et al., 2004).
How to age wine with oak shavings?
It is a common practice in countries such as Chile, Argentina, South Africa, Australia and the United States, and the European Union approved its use in 2006 in the different member countries (EC Regulation No. 1507/2006).
Obviously, the success of this technique will depend on the ability of the winemaker to use these fragments , being able to choose fragments of different varietal origin, size and toast (Figure 2), and to use them in different doses and times.
However, and despite the fact that the use of these oak fragments has two clear advantages compared to the traditional system (low price and speed), their abusive and uncontrolled use can lead to the excessive development of phenolic compounds that affect astringency and structure. of the wine, being able to confer an unwanted bitter taste.
3- Can a wine aged in oak barrels be distinguished from one macerated with oak fragments?
Given the generalization of this process, there is a clear need to legislate this process to ensure correct information to the consumer.
In this sense, the analysis of the chemical composition of wine is presented as the most efficient way to distinguish wines obtained by these two processes. Thus, Hernández-Orte et al. (2014) determined the concentration of 75 volatile compounds in wines obtained by both routes.
The results were useful to develop a criterion that allows an appropriate discrimination of both types of wines , getting to classify in an adequate way 90% of the analyzed samples. Among the compounds analyzed, the authors highlighted the high contents of vanillin, acetovanillone and syringaldehyde in the wines obtained by maceration with oak fragments .
Likewise, the authors indicated the vanillin + acetovanillone / eugenol ratio as the most discriminating ratio to be able to distinguish both processes. Thus, they found values lower than 20 in those cases in which the wine was aged in barrels , and higher values when the wine was obtained by maceration with the oak fragments.