Glossary

Aging
Wines that are stored properly can undergo a number of transformations. In red wines, ideally, the color can change from a rich purple to a lighter old-velvet red and the flavors can soften and lengthen. The primary chemical change has to do with tannins. Tannins are part of the phenolic family and as wine ages, molecules of these phenolics link together forming longer and longer chains. Eventually, these large molecules fall out of the liquid and form part of what is called the sediment. Since tannins can be responsible for an astringent quality to red wines, as they fall out of the liquid, the flavor can soften, leaving behind the more majestic characteristics of the fruit. In many white wines, which do not begin their lives with a high tannin content, the primary changes are a browner color and the flavor takes on stronger characteristics often described as as carmelization.

Appellation
A geographically-based name for a winegrowing region that is believed to show unique characteristics of soil, climate and more. In the United States, appellation names such as Napa Valley are approved by the US Department of Treasury's Tax and Trade Bureau (TTB). The term "sub-appellation" is used informally to refer to a smaller appellation wholly contained within a larger one.

Bud Break
The stage of the growing season, usually early spring in the Napa Valley, when tiny shoots emerge from their buds.

Clone
In viticulture, a clone refers to a vine variety that is selected for specific qualities which result from natural mutations. Cuttings are made from an original "mother vine" that exhibits key characteristics, such as resistance to certain diseases or desired cluster size, taste, smell, etc. Mother vines are often grown at a university and cuttings are supplied to nurseries who in turn sell them to grape growers. Clones such as these come with a registered historical background. » For more information see What is a Clone?

Corked
Wine that is "corked" has been contaminated by its cork stopper and takes on an unpleasant moldly aroma and flavor sometimes described as "wet newspaper." Cork taint affects only a very small percentage of quality wine and it only affects wine on a bottle by bottle basis not all the wine.

Crush
A term for the time of year when Napa Valley is harvesting and crushing its fruit. Crush specifically refers to putting newly picked grapes into a "de-stemmer," a machine that de-stems the fruit and crushes it, releasing juice from the berry.

Enology
The study and science of winemaking.

Fermentation
A chemical process in which yeast consumes the sugar in juice, converting it into alcohol and carbon dioxide. In red and white wine production, the carbon dioxide is released during fermentation, while in sparkling wine, the carbon dioxide is trapped, producing bubbles.

Grafting
The process of physically connecting two plants or pieces of plant tissue together to grow as one. In viticulture, grafting is often used to join a rootstock with a vine variety.

Maceration
After grapes are crushed, maceration is the period in which the juice spends time in direct contact with the skins and seeds in a steeping process that will transfer important characteristics to the finished wine.

Microclimate
A small area with climatic conditions significantly different than the region at large.

Phylloxera
A small aphid that feeds on and fatally damages vine root systems. Phylloxera damages some root systems – primarily vines on their own root, which is why certain rootstocks are selected and used that are resistant.

Pierce's Disease
A fatal disease caused by a bacteria borne by the blue-green sharpshooter or glassy-winged sharpshooter, a leafhopper insect. The bacteria transmitted by the sharpshooter multiply and eventually block the vine's water-conducting systems.

Rootstock
The root system to which a vine variety is grafted.

Sparkling Wine
This bubbly wine is traditionally made from pinot noir, chardonnay and pinot munier. When made in the Champagne region of France, it's called Champagne.

Tannins
A group of chemicals that naturally exist in the skin and seeds of grapes (and many other plants) and give finished wine varying degrees of astringency. For a household example of how tannins can affect the palate, try oversteeped tea.

Trellis systems
The supporting framework on which a vine is trained to grow.

Veraison
The stage of the growing season when young green grapes soften and either turn yellow or red in color depending on the variety. In Napa Valley veraison can occur from late June through mid-August, depending on the year.

Variety
A particular type of grape, such as Chardonnay, Cabernet, Merlot, etc.

Varietal
A wine make from a single grape source, such as Chardonnay, Cabernet, Merlot, etc.

Vintner
A person who produces wine.

Viticulture
The study and practice of growing grapes.

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