Wednesday, March 14, 2012

Available mechanisms for ameliorating tannin-associated wine imbalance

In a previous post on tannins and wine balance, I noted that too much tannin results in a wine that is heavy and rough on the palate and lacks finesse.  Further, if combined with high acidity, the wine will be astringent.  While low levels of tannin may result in an early drinking wine, it may compromise color stability, mouthfeel, and the aging potential of the wine.  This post looks at the tools available to the winemaker to increase/decrease tannin levels as desired.

Increasing Tannin Levels

Tannin levels can be elevated by manipulating aspects of the winemaking process to extract more tannin from a given batch or by adding exogenous tannin during the winemaking process.

The primary integral process for elevated tannin extraction is maceration.  The length of the maceration, and the controlling temperature, are two very important variables in determining tannin extraction levels.  The longer the duration, the higher the levels of tannin and anthocyanin extracted. The higher the temperature (within limits), the higher the tannin extraction rate.  With the higher levels of phenolic compounds that result from post-fermentation maceration, the greater the potential for phenolic polymerization and wines with a softer mouthfeel.

While maceration can be used to extract tannin from both skin and seed, warm processing is a method wherein a quick, hot fermentation is applied to allow extraction of tannin from the skin while minimizing seed contact.

Exogenous tannin addition can be oak (or like products) or powdered.  In the case of oak, the wine is either placed into oak barrels or oak powder, chips, or planks are placed into the container in which the wine resides (The role of oak tannin was discussed in the preceding post.).  Powdered tannin is the end product of mechanical action on grape seeds or various types of wood.  A recent study by Washington State Enologist Jim Harbertson and Australian Wine Researcher Mark Downey called the efficacy of the latter approach into question.  Their key findings were: (i) most of these additives are 12%-48% tannin and (ii) had limited or negative impact on wine quality.  They concluded that the addition of powdered tannin was an unnecessary expense.

Retarding Tannin Levels

"Cold soak" is a method that is utilized in the winery to extract anthocyanins from the grape skin while restricting the level of tannin extraction.  Anthocyanins are more soluble in grape juice than in alcohol so soaking the solids in the juice at 45℉, or lower, will retard the initiation of fermentation while allowing the extraction of color from the skin and limiting the tannin extract.

Fining is a method of clarifying or chemically stabilizing wine using agents that are insoluble in the liquid, have the ability to bind with suspended particles, and are heavy enough to fall to the bottom while retaining the attracted material.  Tannins have an affinity for proteins and protein fining agents such as gelatin, egg white, and isinglass are used to remove tannin from the wine in this manner.  The fined wine is racked off the bottom-resident particles.  Care has to be taken that the wine is not over-fined as the result may be wines that lack complexity, depth, and viscosity and have diminished aging potential.


In addition to raising or lowering tannin levels, tannin-associated wine imbalance can be addressed by actions taken in relation to the other elements of the balance equation.  For example, reducing the acidity levels in high-tannin, high-acid wines will reduce the level of astringency in the wine.  In addition, increasing the level of alcohol in a wine will increase its bitterness but will also reduce the sensation of astringency.  Astringency is also decreased with increasing wine pH.

Hopefully the winemaker will be presented with grapes with the appropriate amount of tannins to ensure the production of balanced wines but if he/she is presented with an excess or surfeit of tannins, the above mechanisms are available for amelioration.

© Wine -- The View From Orlando

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