Enology Notes
Enology Notes #108, November 18, 2005
To: Regional Wine Producers
From: Bruce Zoecklein, Head, Wine/Enology-Grape Chemistry Group, Virginia Tech
Subject: Red Wine Mouthfeel and Fining , Components of Red Wine Mouthfeel
Red Wine Mouthfeel and Fining. We should be carefully evaluating the mouthfeel of the 2005 red wines. Mouthfeel is the perception of the components helping to provide the tactile perception, including polysaccharides, ethanol, glycerin and tannins (Kennedy, 2000).
Generally, lower molecular weight phenols are predominantly bitter, while higher molecular weight tannins are predominantly astringent.
Protein fining agents generally remove higher molecular weight phenols (tannins). However, the difference in the phenol concentration before and after fining is not often large. This suggests that the sensory impact may be due, in part, to changes in the colloidal complexes, not simply a change in phenol concentration. This would help to explain the matrix effect, why different wines react differently to the same type and concentration of fining agent. The composition of colloids, sugars, polysaccharides, etc. are different in different wines.
Most protein fining agents (including yeast fining) are much more ‘forgiving’ (remove less body) when used on young vs. older, aged red wines. For a discussion on protein fining agents, see Enology Notes at www.vtwines.info and Zoecklein et al. (1999).
Components of Red Wine Mouthfeel. The balance of mouthfeel components can be viewed as a wine quality measure. Indeed, balance and harmony are two descriptors used to denote wine quality.
The importance of balance and harmony was certainly highlighted during our difficult 2003 grape growing season in Virginia.
The following is a review of this subject. Additional information can be found under Enology Notes.
Palate Balance Equation
| Sweet | ↔ |
Acid |
+ |
Phenolics |
| Carbohydrates Polysaccharides Ethanol |
Organic acids |
Skin, seed and stem phenols |
Wine structural/textural components interact in certain relationships depicted above, in what I refer to as the palate balance equation.
This inverse relationship suggests that an increase in the perception on one side decreases the perception of components on the other. The converse is also true.
With this in mind, it is easy to understand how the specific components of wine mouthfeel interact, and make some important winemaking inferences.
The sweet elements in a dry red wine are derived from carbohydrates, polysaccharides and mainly ethanol. The acid elements are grape-derived organic acids. The phenolic elements include imput from these components: skin, seeds, stems, plus winemaker intrusion, such as barrels and tannin additions.
Sweet ↔ Acid + Phenols (tannin intensity, astringency, bitterness and dry tannins)
The phenolic elements in this relationship include the perceptions derived from the following: tannin intensity, astringency, bitterness and dry tannins, in a relationship described by Delteil (2003).
The integration of structure and texture components is of importance because our perceptions occur in different parts of the palate, and therefore at different time intervals.
Thus, we taste sweetness at the front of the palate first, followed by acidity on the sides, and finally the phenolic taste of bitterness and tactile responses near the back.
Yet we expect that in a high quality, well-integrated wine, we do not perceive these separate sensations, but a nice, harmonious, whole. The question is how to attain that goal of a harmonious structure and texture. Much of the following relationship has been adapted from Dominque Delteil, formerly from the ICV.
Sweet. In a dry red wine, the sweet elements are frequently not perceived as sweet, due to the impact or balance from the acid and phenolic components.
The primary sweet element in dry red wines is derived from alcohol and polysaccharides. These elements contribute to the perception of body or volume.
Sweet ↔ Acid and Phenols (tannin intensity, astringency, bitterness and dry tannins)
Volume/Body/Sweet
+ Ethanol
+ Polysaccharides and other sugars. (Derived from grapes, yeast, bacteria, oak, commercial products and yeast fining.)
Glycerol, unknown
- Volatile sulfur-containing compounds (VSCs)
The plus sign (+) indicates a positive correlation, while a negative sign (-) indicates a negative correlation. Thus, high alcohol wines, such as California central coast Syrahs or Amidor County Zinfandels, would contain a high concentration of body or volume elements.
We traditionally view volatile sulfur compounds as having mainly an olfactory sensation, which they do. H2S, and the vast array of organic sulfur-containing compounds add to what we call “reductive tone” defect. These also have a major impact on structure that is as dramatic as their impact on odor.
Volatile sulfur compounds decrease the perception of volume/body, thus increasing the perception of the components on the right-hand side of the palate balance equation.
Sweet ↔ Acidity + Phenols (tannin intensity, astringency, bitterness and dry tannins)
Acidity
- Sugar
+ Tannins
+ Certain VSCs, including herbaceous compounds
- Ripe fruit, spicy aromas
- Polysaccharides (grapes, yeast, bacteria, oak, commercial products)
+/- Body/volume
+ Tannin intensity
+ Dryness
+ Bitterness
Anything which increases the perception of acidity usually increases the perception of the phenolic elements also. This usually includes tannin intensity, astringency, bitterness, and dry tannins.
Phenols
The qualitative and quantitative nature of phenols impacts their sensory characteristics. By qualitative, I am referring mainly to phenolic polymerization.
Sweet ↔ Acidity + Phenols (tannin intensity, astringency, bitterness and dry tannins)
Tannin Intensity
+ Acidity
+ Volume compounds, such as extract
+ Yeast in suspension
- Polysaccharides
+ VSCs
+ Herbaceous compounds
+ Non-soluble solids
In our trials on the use of microoxygenation, we have seen a reduction in both tannin intensity and astringency, in part, due to the reduction in red wine herbaceousness. One very important point is that high concentrations of yeast and/or bacteria in wine can impact the perception of the wine structure/textural balance, as indicated.
Sweet ↔ Acidity + Phenols (tannin intensity, astringency, bitterness and dry tannins)
Astringency
+ Grape and oak tannins
+ Acidity
0 Sugar
+ VSCs and herbaceous compounds
- Alcohol up to 14%, + above 14%
+ Non-soluble solids
Qualitative change in phenols, due to oxidative polymerization, results in softer tannins which can reduce the impact from the astringent tannins, lower the perception of the acidity, and increase the perception of volume or body - the sweet elements.
Sweet ↔ Acidity + Phenols (tannin intensity, astringency, bitterness and dry tannins)
Dry Tannins
- Alcohol up to 13%, + above 13%
0 Sugar
+ Grape and oak tannins, including seed tannins
+ Acid, mainly malic and acetic
+ VSCs and herbaceous compounds
+ Yeast in suspension
- Polysaccharides
- Non-soluble solids
The fact that dry tannins are not masked by sugar suggests that this common corrective approach is not very effective.
Sweet ↔ Acidity + Phenols (tannin intensity, astringency, bitterness and dry tannins)
Bitterness
+ Ethanol – more bitterness
+ Grape and oak tannins, including immature seed tannins
+ Acid, specifically malic acid
+ VSCs
+ Yeast in suspension
- Polysaccharides
The negative correlation between polysaccharides and bitterness is a reason for the use of high polysaccharide-producing yeast, and the use of agents such as gums, like Gum Arabic, and yeast fining.
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Dr. Bruce
Zoecklein
Professor and Enology Specialist Head Enology-Grape Chemistry Group
Department of Food Science and Technology, Virginia Tech
Blacksburg VA 24061
Enology-Grape Chemistry Group Web address: http://www.vtwines.info/
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