O

oak - The primary wood used to make barrels for ageing wine. It is hard and watertight but, perhaps more importantly, it imparts phenolics such as tannins and important flavour compounds to wine. Other woods have been used -- chestnut and acacia are two -- but they are often too porous or their tannins too harsh. The most sought after and expensive oak is French in origin, though American oak, while cheaper, is considered by some to be as good or better. Parts of eastern Europe have been important sources as well. Due to the high cost of barrels in general, alternative means of adding oak character have been developed. Oak chips have proven to be a reasonably effective and much cheaper substitute and are legal in most regions, unlike oak essences and extracts which are generally considered to be unacceptible shortcuts. See also barrel ageing.

oak aged - Applied to wine that has been aged in oak barrels. See also barrel ageing.

oaky - a sensory evaluation used to describe the oak flavor in a wine.

Oechsle scale - System used in Germany to measure the sugar in unfermented grape juice. See also Brix scale and must weight.

oenology - The science or study of wine and wine-making. An expert in the field is called an oenologist. The American spelling is "enology".

oenophile - A wine connoisseur. The American spelling is "enophile".

off dry - Having just a trace of sweetness.

oidium - French - Term for the fungal vine disease "powdery mildew".

oily - A term applied to a wine with a viscous texture, or simply a wine that is low in acidity and feels flabby in the mouth.

Oloroso - One of the two basic types of sherry, it differs from fino in that it is not affected by the flor yeast and as a result is subject to a certain amount of oxidation. Oloroso is fortified to a higher alcohol percentage -- usually about 18% compared with the 15 to 15.5% for fino. It ranges from dry to sweet, though the best and most typical examples are dry. Poor versions are simply cheap sherry with added colour and sweetness.

open - Said of a wine that is developed and ready to drink. Opposite of closed.

organic wine - The word "organic" is inexact, with definitions ranging from simply practising agriculture without the use of synthetic chemicals to a philosophy of farming that recognizes biodiversity and emphasizes sustainability. Where wine is concerned the term refers to the growing of grapes as well as to the processes of winemaking. Erosion, pesticides, fertilizers, cultured yeasts, chemical additives like sulphur dioxide, fining agents and filtering methods are just some of the concerns of organic winemakers. While efforts are being made to regulate organic farming and winemaking methods worldwide, the complexity of the issue makes this task difficult. Despite the lack of proper definitions however, there is a growing trend among winemakers to adopt organic farming practices, as well as a growing awareness among consumers of the health and environmental merits of organic wine.

Ouzo - A Greek anise-flavored liqueur that is widely consumed in Greece. The name dates back to the late 19th century, but is of uncertain origin. It is similar to pastis, but a little sweeter and smoother, so that it is pleasant to drink either "straight" or mixed with water. The best Ouzo it is considered that of the island of Lesvos. Most cafe owners in Greece will admit that the best ouzo comes from this island and they probably carry one of the more popular Lesvos brands.

overcropped - A vine which carries more crop than it can reasonably ripen. Vines which aren't pruned drastically enough tend to set too much crop. Wine produced from fruit of an overcropped vine is always poorer in quality than if the crop were normal size.

oxidation - Chemical changes brought about by exposure to oxygen. In wine, oxidation can happen at any time after the grapes have been crushed. The most important changes occur in the phenolics. Colours, both red and white, change gradually to tawny brown and the wine eventually tastes thin and stale with a flat aroma. Winemakers take great pains to avoid exposing their wine to excessive amounts of air. Some wines, however -- Oloroso sherry and madeira for example -- actually benefit from a certain amount of oxidation, giving them unusual and complex character.

oxidized - Refers to a wine that has suffered oxidation.