Premature oxidation, (sometimes shortened to premox, or POx) is a flaw that occurs in white wines, when the presumably ageworthy wine is expected to be in good condition yet is found to be oxidised and often undrinkable. In particular the affliction has received attention in connection to incidents of whites produced in Burgundy. [1] [2] The afflicted vintages are predominantly from the late 1990s, and in particular those of 96, 97 and 98, [3] until 2002. [4] There have also been reports of premature oxidation occurring in wines from Australia, Alsace, Germany, and Bordeaux. [5]
Clive Coates, MW has stated that "Poorly-performing corks are the main culprits behind prematurely aged white Burgundy", [3] while Pierre Rovani of The Wine Advocate has stated the contrary, "corks are not the issue". [2] Allen Meadows has speculated that "based on what we know today, the most likely source of the problem is cork-related, though it appears this has been exacerbated by generally lower levels of SO2", while Steve Tanzer believes it to be a combination of several factors that involve corks, global warming resulting in overripe fruit, excessive stirring of the lees, and insufficient use of sulfur dioxide. [2] Roger Boulton, professor of UC Davis, agreed with the probability of multifactorial causality, stating, "there are likely to be both closure issues and wine chemistry issues, so looking for the [single] answer will be like missing the bus". [5]
The French oenologists Denis Dubourdieu and Valérie Lavigne-Cruege launched a theory that with the recent trends of abstaining from the use of herbicides and letting grass grow freely in the vineyards of Burgundy, the grass competing with vines for water in conjunction with a warm vintage may cause the vines to endure extreme stress. As a result, grapes grown on highly stressed vines may have insufficient quantities of glutathione, a compound that functions as an essential antioxidant during the fermentation process. [1]
According to Michel Bettane, Burgundy producers reacted by taking steps to address the possible causes by heightened scrutiny of cork quality, more awareness of possible sulfur dioxide insufficiency, and a decrease of the practice of batonnage, the stirring of the lees that adds richness to the wines but also increases oxygen contact. [1]
In December 2006, Jamie Goode published an analysis of the problem of premature oxidation in The World of Fine Wine and explores some possible solutions. [5]
Premature oxidation is a risk in organic winemaking, in which a lowered sulfite content is stipulated. [6] Use of bâtonnage is known to increase premature oxidation. [7]
Wine is an alcoholic drink made from fermented fruit. Yeast consumes the sugar in the fruits and converts it to ethanol and carbon dioxide, releasing heat in the process. Though wine can be made from a variety of fruit crops such as plum, cherry, pomegranate, blueberry, currant and elderberry, it is most often made from grapes, and the term "wine" generally refers to grape wine when used without a qualifier.
Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation. The acetic acid bacteria consist of 10 genera in the family Acetobacteraceae. Several species of acetic acid bacteria are used in industry for production of certain foods and chemicals.
Sulfur dioxide or sulphur dioxide is the chemical compound with the formula SO
2. It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of sulfur-bearing fossil fuels. It was known to alchemists as "volatile spirit of sulfur" since at least 16th century.
Champagne is a sparkling wine originated and produced in the Champagne wine region of France under the rules of the appellation, which demand specific vineyard practices, sourcing of grapes exclusively from designated places within it, specific grape-pressing methods and secondary fermentation of the wine in the bottle to cause carbonation.
Bottle variation is the degree to which different bottles, nominally of the same product, can have different taste, smell, etc.
Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. There is evidence that suggests that the earliest wine production took place in Georgia and Iran around 6000 to 5000 B.C. The science of wine and winemaking is known as oenology. A winemaker may also be called a vintner. The growing of grapes is viticulture and there are many varieties of grapes.
White wine is a wine that is fermented without skin contact. The colour can be straw-yellow, yellow-green, or yellow-gold. It is produced by the alcoholic fermentation of the non-coloured pulp of grapes, which may have a skin of any colour. White wine has existed for at least 4,000 years.
Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.
Muscadet is a French white wine. It is made at the western end of the Loire Valley, near the city of Nantes in the Pays de la Loire region. It is made from the Melon de Bourgogne grape, often referred to simply as melon. While most appellation d'origine contrôlée wines are named after their growing region, or in Alsace after their variety, the name Muscadet refers to an alleged characteristic of the wine produced by the melon grape variety: vin qui a un goût musqué. However, according to wine expert Tom Stevenson, Muscadet wines do not have much, if any, muskiness or Muscat-like flavors or aromas.
In horticulture, lime sulfur (lime sulphur in British English, see American and British English spelling differences) is mainly a mixture of calcium polysulfides and thiosulfate (plus other reaction by-products as sulfite and sulfate) formed by reacting calcium hydroxide with elemental sulfur, used in pest control. It can be prepared by boiling in water a suspension of poorly soluble calcium hydroxide (lime) and solid sulfur together with a small amount of surfactant to facilitate the dispersion of these solids in water. After elimination of any residual solids (flocculation, decantation and filtration), it is normally used as an aqueous solution, which is reddish-yellow in colour and has a distinctive offensive odor of hydrogen sulfide (H2S, rotten eggs).
A wine fault is a sensory-associated (organoleptic) characteristic of a wine that is unpleasant, and may include elements of taste, smell, or appearance, elements that may arise from a "chemical or a microbial origin", where particular sensory experiences might arise from more than one wine fault. Wine faults may result from poor winemaking practices or storage conditions that lead to wine spoilage.
The glossary of wine terms lists the definitions of many general terms used within the wine industry. For terms specific to viticulture, winemaking, grape varieties, and wine tasting, see the topic specific list in the "See also" section below.
The traditional method is the process used in the Champagne region of France to produce Champagne. It is also the method used in various French regions to produce sparkling wines, in Spain to produce cava, in Portugal to produce Espumante and in Italy to produce Franciacorta. The method is known as the méthode champenoise, but the Champagne producers have successfully lobbied the European Union to restrict the use of that term within the EU only to wines produced in Champagne. Thus, wines from elsewhere cannot use the term "méthode champenoise" on products sold in the EU, and instead the term "traditional method" or the local language equivalent. South African wines from the Western Cape are labelled with the term Methode Cap Classique. Some wine producers in countries outside the EU may disregard EU labeling laws and use méthode champenoise or even "Champagne" on labels for products not exported to the EU, but this usage is decreasing.
Alternative wine closures are substitute closures used in the wine industry for sealing wine bottles in place of traditional cork closures. The emergence of these alternatives has grown in response to quality control efforts by winemakers to protect against "cork taint" caused by the presence of the chemical trichloroanisole (TCA).
Jamie Goode is a British author with a PhD in plant biology, and a wine columnist of The Sunday Express. Goode also contributes to wine publications such as Harpers, The World of Fine Wine, Decanter, GrapesTALK and Sommelier Journal. Goode played guitar in folk rock band Tintagel which released the album Sword and Stone in 1991.
The aging of wine is potentially able to improve the quality of wine. This distinguishes wine from most other consumable goods. While wine is perishable and capable of deteriorating, complex chemical reactions involving a wine's sugars, acids and phenolic compounds can alter the aroma, color, mouthfeel and taste of the wine in a way that may be more pleasing to the taster. The ability of a wine to age is influenced by many factors including grape variety, vintage, viticultural practices, wine region and winemaking style. The condition that the wine is kept in after bottling can also influence how well a wine ages and may require significant time and financial investment. The quality of an aged wine varies significantly bottle-by-bottle, depending on the conditions under which it was stored, and the condition of the bottle and cork, and thus it is said that rather than good old vintages, there are good old bottles. There is a significant mystique around the aging of wine, as its chemistry was not understood for a long time, and old wines are often sold for extraordinary prices. However, the vast majority of wine is not aged, and even wine that is aged is rarely aged for long; it is estimated that 90% of wine is meant to be consumed within a year of production, and 99% of wine within 5 years.
The history of Champagne began when the Romans planted vineyards in this region of northeast France in the 5th century, or possibly earlier. Over centuries, Champagne evolved from being a pale, pinkish still wine to a sparkling wine. When Hugh Capet was crowned King of France in 987 at the cathedral of Reims, he started a tradition that brought successive monarchs to the region—with the local wine being on prominent display at the coronation banquets. The early wine of the Champagne region was a pale, pinkish wine made from Pinot noir.
This glossary of winemaking terms lists some of terms and definitions involved in making wine, fruit wine, and mead.
Ullage is a winemaking term that has several meanings but most commonly refers to the headspace of air between wine and the top of the container holding the wine. It can also refer to the process of evaporation that creates the headspace itself or it can be used as a past tense verb to describe a wine barrel or bottle that has gone through the evaporation process. The headspace of air is a mixture mostly of alcohol and water vapors with carbon dioxide that is a by-product of the fermentation process. In containers that are not completely air-tight, oxygen can also seep into this space. While some oxygen is beneficial to the aging process of wine, excessive amounts can lead to oxidation and other various wine faults. This is why wine in the barrels is regularly "topped up" and refilled to the top with wine in order to minimize the head space. In the bottle, the ullage or "fill level" of the wine can be an important indicator of the kind of care and storage conditions that the wine was kept in. After-market resellers and wine auction houses will often inspect the ullage levels of older vintages to determine the potential quality and value of wine.
The role of yeast in winemaking is the most important element that distinguishes wine from fruit juice. In the absence of oxygen, yeast converts the sugars of the fruit into alcohol and carbon dioxide through the process of fermentation. The more sugars in the grapes, the higher the potential alcohol level of the wine if the yeast are allowed to carry out fermentation to dryness. Sometimes winemakers will stop fermentation early in order to leave some residual sugars and sweetness in the wine such as with dessert wines. This can be achieved by dropping fermentation temperatures to the point where the yeast are inactive, sterile filtering the wine to remove the yeast or fortification with brandy or neutral spirits to kill off the yeast cells. If fermentation is unintentionally stopped, such as when the yeasts become exhausted of available nutrients and the wine has not yet reached dryness, this is considered a stuck fermentation.
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