The visual aspect is the first sensation we perceive in a glass of wine. Its color, brightness and transparency must be correct, as they are indicators of quality and aspects related to its aroma and flavor.
Climate change is causing an increase in temperatures, which would mean making wines with higher alcohol content. However, the trend is different, with a growing preference for making wines with a lower alcohol content. This produces a decompensation between phenolic and technological maturity, decreasing the concentration of anthocyanins, extracted tannins and, with it, the dye intensity and, above all, its stabilization.
To compensate for the phenolic maturity, tannins are used during the devatting, when polishing the structure of the wines, softening the tannins (in the greenest wines) or enhancing the tannin load where there has been less extraction. We are trying to create a balanced wine, prepare it for aging or tannic enhancement.
In this article, we’ll talk about one of the strategies for stabilizing red wines, using Agrovin’s Tanicol Vintage and Tanicol RedSense. But before going into detail, it is important to be clear about what exactly provides red wine with its color.
Compounds responsible for the color of wine
Anthocyanins are the compounds responsible for the bluish-red color of wines, and, with the exception of some dyeing varieties, are found in the skin of red grapes.
The color of the wine will depend on several factors: the temperature during maceration, the extraction processes and the pH.
Its vividness will depend on the balances between the monomeric forms of the anthocyanins, which will be governed by the pH, tending more to the red or blue tones as we see in the following diagram:
Figure 1. Balance of anthocyanins as a function of pH (Zamora 2013)
As shown in the figure, the wine must be balanced between red, blue and colorless forms. At the pH of most red wines, between 3.5 – 4, the coloration from anthocyanins is between 20-30%. In other words, between 70-80% of anthocyanins could potentially participate in the wine’s color (Álvaro Peña, 2006).
Let’s go to the lab…
The AGROVIN Technical Department, together with the University of Turin, did research to see the effect of added condensed and hydrolysable tannin during the fermentation of the red grape. The project is entitled “Tests for stabilization of the coloring fraction of Barbera grapes using tannins in fermentation”.
The Barbera grape variety was used for the experiment. It’s an Italian variety that is low in tannins and has a high content of coloring matter. These characteristics lead to a loss of color throughout the winemaking and aging process.
Condensed and hydrolysable tannins were added to the sample, obtaining the following results:
Table 1. Measurement of total anthocyanins (mg/l) during fermentation (AGROVIN, 2018)
The addition of the ellagic tannin mainly causes an increase in the concentration of anthocyanins from the first moments of fermentation. This is due to its protective effect against oxidation, protein precipitation and co-pigmentation phenomena.
After bottling the wines, the concentrations of monomeric and total anthocyanins are observed, obtained with the use of the different tannins:
Graph 1. Content of total and monomeric anthocyanins (mg/l) in the different tests (AGROVIN, 2018)
An increase of 20% in the concentration of total anthocyanins is observed with the use of ellagic tannin, and almost 10% with the use of condensed tannin. It is also observed that the use of condensed tannin lowers the concentration of easily oxidisable monomeric anthocyanins.
This last graph shows the distribution of anthocyanins in various polymerisation phases.
Graph 2. Distribution of anthocyanins in different phases of polymerisation (AGROVIN, 2018)
In addition, it can clearly be seen that the highest percentage of polymerised anthocyanins, and therefore, the most stable over time, is obtained with the use of condensed tannin.
The conclusion drawn from the experiment is that the use of tannins has a positive effect on the increase in the concentration of anthocyanins, on the coloring fraction and on its stabilization. A combination of both condensate and ellagic tannins is the most effective treatment for achieving a greater increase in color in red wines.
Let’s dive a little deeper…
How are oenological tannins classified?
They can be classified into two large groups: condensed tannins and hydrolysable tannins.
- Condensed tannins
One type of condensed tannins are those that we can find in grape seeds and in the skin cells. These tannins have a high number of units, are polymerised and vary depending on where in the grape they are found. For example, in seeds, the degree of polymerisation is 11, while in skins it is 30. The degree of polymerisation, together with the number of galloylated units, will influence the astringency of the wine. An example of a condensed tannin is Tanicol VINTAGE.
What is TANICOL VINTAGE?
It is a 100% grape seed-based tannin with a great effect on color stability.
What are its characteristics?
- It has a great reactivity and ability to combine with anthocyanins.
- It increases the phenolic potential of wine providing robustness and structure.
- It’s a very easily-dissolvable tannin.
- It has great antioxidant power,
- It is excellent in fermentation and discovers where the aroma of the wines increases, marking the varietal characteristics.
- It improves dye stability.
Learn more about Tanicol Vintage here
- Hydrolysable Tannins
They do not come naturally from grapes, but can be present in wines when transferred from wooden barrels or through the use of specific oenological tannins. These tannins are divided into two groups: Gallic tannins (the main source of gallic tannin is Tara and walnut) and Elagic tannins (the main source of ellagic tannin are oak and chestnut).
What are the properties of oenological tannins?
- Effect on color
This depends on the type of tannin used.
For example, condensed tannins contribute to color stabilization by facilitating anthocyanin-tannin combinations. While gallic and ellagic tannins cannot participate in this process, they do contribute to protecting anthocyanins from oxidation
Another aspect to consider is that tannins contribute to increasing the color of wine through the co-pigmentation phenomenon.
- Contribution of body and structure
The effect of oenological tannins on the wine’s body and structure seems to be evident, since, in most cases, when adding tannins to wine, there is a noted increase in the total polyphenol extract (TPE), as well as an increase in the sensation of body and structure (Pardo, 2001). To achieve these effects, condensed tannins and ellagic tannins seem to be the most advisable (Vivas, 1997).
- Protection against Oxygen
The protection against oxygen derived from tannins occurs in three ways: direct consumption of oxygen, the chelating effect of heavy metals and the inhibition of enzymes with oxidase effect.
- Protein reactivity
The peptides and proteins of the musts react with the tannins, causing their precipitation. To minimize this effect, target tannins are used that serve as anchors for proteins in the early stages of fermentation.
What is “TANICOL RedSense”, the granulated tannin for fermentation?
TANICOL RedSense is a combination of different types of tannins to stabilise red wines, increase the aromas of red and black fruit and improve the structure and body of the wine.
It is an ideal combination of ellagic tannin (chestnut), condensed tannin (grape seed) and red fruit tree tannin, perfect for fermentation.
What are its characteristics?
- It dissolves easily due to its granular format.
- Due to the co-pigmentation caused by the ellagic tannin, there is a positive effect on the color intensity of red wines.
- Stable pigments are formed that stabilize the coloring matter.
- It has an antioxidant effect.
- It causes the precipitation of the peptides and proteins in the must, thus protecting the grape’s natural phenols.
- It improves the structure of the wine.
It increases the red fruit aromas, increasing the content of the compounds responsible.
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- Preservation of color in wines made using heat treatments, such as Flash Detente and Thermovinification.
Learn more about Tanicol RedSense here
For more information on oenological tannins, contact Agrovin