Technical Wine Terms U to Z

  • Unoaked: often specified by a producer when it also releases an oaked version of the same variety. Particularly used for Chardonnay which is closely associated with fermentation and/or ageing barrels. The most likely scenario is that an unoaked wine is fermented and aged in stainless steel, with cement tanks coming next in terms of probability. Wines made using less common materials such as terracotta, or other wood species are, of course, very unlikely to be labelled as "unoaked". For more detail see The Ultimate Guide to Oak in Winemaking.

  • Varietal: is both a noun and an adjective. As an adjective, it denotes the defining characteristics of wines made from a particular grape variety (particularly flavor and aroma). As a noun, it denotes a wine made predominantly or exclusively from a single grape variety. Because of this, the term is increasingly (mis)used to mean 'grape variety'.

  • Varietal labeling: is the practice of naming and labeling a wine with the name of the grape variety used to make it. Most varietal wines are required by law to contain at least 85% of the grape variety stated on the label.

  • Veraison: is a French term used in viticulture to describe the period in the grapevine’s growth cycle when berries change color and become softer. After flowering, and during the early development stages of the bunches, all grapes have a herbaceous green color. During veraison, white grape varieties turn a lighter, more transparent yellow, while black grape varieties become red.

    Depending on the climatic conditions, particularly temperature, this stage takes one to two weeks. Each berry changes color at its own pace depending on when its flower was formed , and also its exposure to sunlight and heat. In the northern hemisphere, veraison generally occurs between late July and early August, while in the southern hemisphere it occurs between late January and early February.

    Veraison is considered the starting point of grape maturation because sugars start to accumulate in the pulp, and color and tannins develop in the skins. It is closely watched by viticulturalists and winemakers, as it can have a direct impact on the date of the harvest, the ripening of the fruit and the quality of the wine.

  • Vertical: refers to a wine collection comprising various vintages of a single cuvee. Verticals of a given wine are often used in professional wine tastings to demonstrate the effects of both vintage variation and bottle age. Although it is not always clear which of these influences is responsible for a particular characteristic in the wine, this uncertainty adds to the intrigue and mystique of vertical tastings. A 'vertical' is not necessarily made up of consecutive years, although greater prestige is held by unbroken series. This applies particularly to historic wines from Bordeaux and Burgundy, and most notably long-lived wines such as Sauternes; Chateau d'Yquem verticals have been known to span more than 125 years and be worth millions of dollars.

  • Vigor: refers to the vegetative growth of the vine, which depends on many factors including soil, availability of water and nutrients, climate, vineyard practices and the length of the growing season. It has a direct impact on the quality of grapes produced, as both high and low vigor can severely affect the vine's ability to transfer the vital nutrients necessary to achieve optimum fruit maturity.

  • Vin de Paille: a French term for sweet wine made from grapes that have been dried out to concentrate the sugar levels in their juice. Traditionally, this drying process was carried out on straw mats (paille is French for 'straw'). Produced via mutage, the alcoholic strength of these wines is generally between 15% and 20%. Vins de paille are different from botrytized wines in that the grapes are not subject to noble rot, and from ice wine, in that the sugars are concentrated by sunshine rather than through the grapes freezing on the vine. The German equivalent is Strohwein and Italian passito wines (such as Vin Santo) are made in a similar way.

  • Vin doux naturel: a French term used for a style of wine with a high quantity of natural sugar. These wines are made by the mutage method, which involves the addition of grape spirit to stop fermentation – thereby retaining natural sugar. Grenache and Muscat are the most common grape varieties used for the production of vins doux naturel. According to French appellation laws, these wines should have an alcoholic strength of 15% to 18%, and a potential alcohol of at least 21.5%.

  • Vine grafting: a process of fusing two different plant tissues with the aim of utilizing the benefit of both. In viticulture, the process is of immense importance as it has proven to be the most effective way of controlling the deadly phylloxera louse. It also improves resistance to viral diseases and improves the quality of the grapes.

    A classic vine grafting would involve a phylloxera-resistant American rootstock and the quality Vitis vinifera vine (see description below).

  • Vine training: a way to establish and manipulate a canopy system so that the vine produces the desired quality and quantity of fruit. The main factors which influence how a vine is trained include climatic conditions, the degree of mechanization required and disease control. In many wine-producing regions, vines are trained according to local traditions. However, other regions have adopted modern vine training techniques such as Smart-Dyson, Geneva Double Curtain and Sylvos.

  • Vin Jaune: a dry, sherry-like wine produced in the Jura region of eastern France. It is made from Jura's flagship grape, Savagnin, which is picked late in the season for optimal ripeness. The wine is matured in barrels for several years under a naturally occurring film of yeast, during which time it develops rich, nutty flavors and the deep yellow color which gives the wine its name (jaune is French for 'yellow'). The principal appellation for these wines is Chateau-Chalon.

  • Vinolok: a brand of glass closures available in different shapes and sizes. They feature a sealing ring made of EVA (ethylene vinyl acetate copolymer), which contains no phthalates or allergens. They can be inserted by hand or on automated bottling lines. As with screwcaps, bottles can be stored upright. Cost tends to be around 50 percent more than the highest spec screwcap, though can be considerably less than the very best natural corks.

  • Vitis labrusca: the native grapevine of North America. Unlike Vitis vinifera (see below), it lacks pronounced varietal characters. Instead, Vitis labrusca produces grapes with a strong, distinct flavour, often described as 'foxy'. It does not have commercial significance except in some north-eastern American states.

  • Vitis vinifera: the vine species which originated in Europe and is responsible for the majority of world wine production; for that reason, it is also known as the 'common grapevine'. Its superior varietal characteristics makes it the preferred choice for quality wine production.

  • Wild yeast: ambient, or naturally occurring, yeast used in wine production rather than a cultured yeast strain. Using wild yeasts has both advantages and disadvantages. Wines fermented this way display added complexity, but they often lack consistency.

  • Wine of Origin (WO): the wine law for South African winegrowing areas. It consists of four categories:

    • Geographical Units – generic labeling terms, such as 'Northern Cape' or 'Western Cape'
    • Regions – large regions encompassing many districts, such as 'Coastal Region'
    • Districts – such as 'Paarl', within the Coastal Region
    • Wards – the smallest of all Wine of Origin (WO) categories. Examples are 'Franschhoek Valley' in the Paarl district and Constantia in the Cape Point district.

  • Yield: a term denoting the total production of grapes from a vine or vineyard in particular, but sometimes also from a region as a whole. Yield is related to vine vigor (see above) and in most cases indicates the quality of the grapes, with extraordinarily high yield often associated with low quality. Some fine wine regions, therefore, have clearly laid out yield limits as part of the local appellation laws.

    Yield is measured in various ways, depending on geography. The most common units are tonne/ha (or ton/ha) and kgs/acre. It is also common to describe yield in hectoliters/ha (hl/ha), to refer to the amount of wine that can be made from a particular area's production.

  • Zork: a plastic cork-like stopper sealed with an inner foil, which allows some transfer of oxygen. An outer plastic strip coils around the top of the bottle and is peeled off by the consumer. Sparkling wines using Zorks can be resealed, and the stopper can be reused and recycled.