Maturation of Wine
Wine Blending
After maturation, wines will have a final evaluation by the winemaker to determine the quality of each barrel or tank and may require blending in order to produce wines with consistent style from year to year to compensate for varying environmental and viticultural circumstances. Blending wines is at the heart of many great wines, be they from Rioja, Bordeaux, California, South Africa, or Australia. The famous clarets from the Medoc, northwest of Bordeaux, are all blends of red grape varieties, mainly Cabernet Sauvignon, Cabernet Franc, Merlot, and Malbec.
Blending Rules for the United States
Each country has its special rules concerning blending and labeling of wines. In California, for example, in order to state a varietal name on the label, it is mandatory to blend at least 75 percent of that specific variety in the wine. If the blending is such that there is less than 75 percent of any variety, the wine has to be labeled as generic wine.
Correcting Deficiencies
The parameters that can be easily corrected by blending are: volatile acidity, pH, alcohol, color, tannin, varietal aroma, freshness and fruitiness, oak flavor, residual sugar, bitterness, and off-flavor. Some of these parameters are in excess (defining the wine as having some noticeable flaw) or in deficiency (causing the wine to be considered unbalanced, of lower quality). Blending may bring these parameters to the desired level, or at least make them tolerable.
When to Blend Wines
There are two basic approaches when to blend wines. One is to blend the wine early, which in practice means once the malolactic fermentation has been completed. For instance, in Bordeaux, this would be in February or March following the vintage. The second approach is to keep the various parcels separate until the maturation is completed but before fining and tartrate stabilization. That way the winemakers can monitor the evolution in tank/barrel of each grape variety and each significant block in the vineyard.
Wine Blending Methods
The mixing is important, because it must ensure that the blend is homogenous. In order to ensure a homogenous mix, the volume of the blend must be turned over at least five times. If the volume of the blend and consequently the required blending tank is small enough, pump-overs with pumps and hoses will be sufficient if circulation is done from the bottom valve or top of the tank.
Pearson Square
Pearson's square is a blending tool used for twocomponent blends and is adaptable for larger blends. The square utilizes a desired value and the ratio of the same component values of two wines.
Organoleptic Approach
Some winemakers combining wines with different sensory characteristics (e.g., oak aroma, fruitiness) with the goal in creating a wine that is greater than the sum of its parts- one with a carefully balanced harmony of notes in which no one note is dominant.
Marrying Period
Pretesting of the trial blend, including stability tests, helps avoid surprises and can be used to help develop appropriate treatments. Trial blending is recommended to be in at least two stages, tasting trials and then precisely made larger amounts (greater than 10L) of the preferred blend for marrying and stability tests as well as to confirm the tasting results.
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