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general_discussion [2018/11/24 17:39]
roumegaire
general_discussion [2018/11/24 17:41]
roumegaire
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 ===== There are Two Distinct Types of Oxidation In Bottled Wine ===== ===== There are Two Distinct Types of Oxidation In Bottled Wine =====
 \\  The oxidation of bottled wine actually consists of two distinct but chemically coupled types of oxidation reactions. One type of oxidation results in the color changes we associate with premature oxidation. The other type of oxidation results in the changes in aromas and flavors referred to above.\\ \\ The first type of wine oxidation is oxidation of flavonoid phenols, which are polyphenolic compounds located in the grape skins, seeds and stems. This type of phenolic compound is generally associated with pressing or extractive techniques. Thus, wines which are subject to more vigorous pressing exhibit considerably higher levels of flavonoid phenols and wines which are made with very gentle pressing and no extractive techniques exhibit very little in the way of flavonoid phenols. When flavonoid phenols are oxidized they result in color changes in the wine (browning), which change the wine over time from bright yellow to increasingly deeper shades of gold and finally brown color. There is another group of phenolic compounds in grape juice, called non-flavonoid phenols, which make up the largest amount of the phenols present in white wine and are found primarily in the pulpy part of the grape. While non-flavonoid phenols also oxidize over time in wine, they do not produce any detectable changes in color, aromas or flavors. \\ \\ The second type of wine oxidation is oxidation of ethanol, the alcohol produced by the fermentation process. The ethanol is oxidized by hydrogen peroxide (H2O2) present in the wine, which results in acetaldehyde. The primary source of hydrogen peroxide in the wine is from the oxidation of phenols. When acetaldehyde reaches the threshold detection level (generally between 8 and 10 ppm depending on the individual),​ we perceive the oxidized aromas and/or flavors described above. \\ \\ While the combination of an oxidized color and oxidized aromas and flavors most frequently occur simultaneously,​ it is certainly possible to have a wine with a brilliant youthful-appearing color which exhibits oxidized aromas and flavors. Conversely, it is also possible to have a wine which exhibits considerable browning but no oxidized flavors or aromas. Personally, I’ve experienced more than one example of each. Moreover, it is also possible to reduce or eliminate the color changes which normally take place over time by means of a controversial technique known as “hyper-oxidation,​” or sometimes more gently referred to as “browning of the must,” which is discussed below. \\ \\ There is a chemical interrelationship between the two types of oxidation. Wine chemists refer to this as “coupled oxidation.” One interrelationship between the two different oxidation processes is that the oxidation of phenols in the wine creates hydrogen peroxide (H2O2) as a byproduct which, unless it reacts with free sulfur dioxide (free SO2), will oxidize ethanol into acetaldehyde. Thus, the oxidation of phenols eventually leads to the oxidation of ethanol once the free SO2 is exhausted. A second interrelationship is that the phenols prevent the oxidation of ethanol that would otherwise directly occur from free sulfate radicals derived from the SO2 added to the wine. Thus, from the perspective of oxidation of ethanol into acetaldehyde,​ there is a mutual interdependence between the phenols and the SO2 added to the wine to prevent oxidation. The third interrelationship relates to the phenols ability to absorb or remove oxygen as the phenols are oxidized. Due to some unique chemical properties, phenols in the wine act both as substrates for oxidation (in layman’s terms, as vehicles for oxidation or as the component which is actually oxidized) and as buffers to the oxidation of ethanol (in layman’s terms, as inhibitors to the oxidation of ethanol.) It is generally agreed that the flavonoid and non-flavonoid phenols in the wine are the primary buffer or barrier to the oxidation of ethanol in white wine. Sulfur dioxide is also a barrier to oxidation, but its role is to react with and effectively remove hydrogen peroxide. \\  \\  The oxidation of bottled wine actually consists of two distinct but chemically coupled types of oxidation reactions. One type of oxidation results in the color changes we associate with premature oxidation. The other type of oxidation results in the changes in aromas and flavors referred to above.\\ \\ The first type of wine oxidation is oxidation of flavonoid phenols, which are polyphenolic compounds located in the grape skins, seeds and stems. This type of phenolic compound is generally associated with pressing or extractive techniques. Thus, wines which are subject to more vigorous pressing exhibit considerably higher levels of flavonoid phenols and wines which are made with very gentle pressing and no extractive techniques exhibit very little in the way of flavonoid phenols. When flavonoid phenols are oxidized they result in color changes in the wine (browning), which change the wine over time from bright yellow to increasingly deeper shades of gold and finally brown color. There is another group of phenolic compounds in grape juice, called non-flavonoid phenols, which make up the largest amount of the phenols present in white wine and are found primarily in the pulpy part of the grape. While non-flavonoid phenols also oxidize over time in wine, they do not produce any detectable changes in color, aromas or flavors. \\ \\ The second type of wine oxidation is oxidation of ethanol, the alcohol produced by the fermentation process. The ethanol is oxidized by hydrogen peroxide (H2O2) present in the wine, which results in acetaldehyde. The primary source of hydrogen peroxide in the wine is from the oxidation of phenols. When acetaldehyde reaches the threshold detection level (generally between 8 and 10 ppm depending on the individual),​ we perceive the oxidized aromas and/or flavors described above. \\ \\ While the combination of an oxidized color and oxidized aromas and flavors most frequently occur simultaneously,​ it is certainly possible to have a wine with a brilliant youthful-appearing color which exhibits oxidized aromas and flavors. Conversely, it is also possible to have a wine which exhibits considerable browning but no oxidized flavors or aromas. Personally, I’ve experienced more than one example of each. Moreover, it is also possible to reduce or eliminate the color changes which normally take place over time by means of a controversial technique known as “hyper-oxidation,​” or sometimes more gently referred to as “browning of the must,” which is discussed below. \\ \\ There is a chemical interrelationship between the two types of oxidation. Wine chemists refer to this as “coupled oxidation.” One interrelationship between the two different oxidation processes is that the oxidation of phenols in the wine creates hydrogen peroxide (H2O2) as a byproduct which, unless it reacts with free sulfur dioxide (free SO2), will oxidize ethanol into acetaldehyde. Thus, the oxidation of phenols eventually leads to the oxidation of ethanol once the free SO2 is exhausted. A second interrelationship is that the phenols prevent the oxidation of ethanol that would otherwise directly occur from free sulfate radicals derived from the SO2 added to the wine. Thus, from the perspective of oxidation of ethanol into acetaldehyde,​ there is a mutual interdependence between the phenols and the SO2 added to the wine to prevent oxidation. The third interrelationship relates to the phenols ability to absorb or remove oxygen as the phenols are oxidized. Due to some unique chemical properties, phenols in the wine act both as substrates for oxidation (in layman’s terms, as vehicles for oxidation or as the component which is actually oxidized) and as buffers to the oxidation of ethanol (in layman’s terms, as inhibitors to the oxidation of ethanol.) It is generally agreed that the flavonoid and non-flavonoid phenols in the wine are the primary buffer or barrier to the oxidation of ethanol in white wine. Sulfur dioxide is also a barrier to oxidation, but its role is to react with and effectively remove hydrogen peroxide. \\ 
-===== **The incidence of premature oxidation by vintage** =====+===== The incidence of premature oxidation by vintage =====
  The premature oxidation problem, which began with the 1995 vintage, was not really recognized as a systemic problem until the fall of 2003, when the 1996 vintage reached seven years of age. At that time a small but discernable percentage of the wines began to exhibit premature oxidation symptoms similar to those which the 1995 vintage began exhibiting about a year earlier. When an inordinately high number of the 1995 vintage whites appeared to be partially or fully oxidized, it seemed inexplicable and people naturally sought to explain the problem as somehow related to the vintage (and there had been a considerable amount of rot in 1995). When the 1996 vintage started to show the same problems, despite being considered an ultra-clean,​ high acid and classic vintage, alarm bells started going off. Each subsequent vintage has exhibited similar problems beginning about 6.5 to 7 years after the vintage (although the vintages subsequent to 1999 have a lower incidence of outright oxidation than do 1995, 1996 and 1999, the incidence of advanced wines has been higher in a majority of the subsequent vintages.)\\ \\  The first public commentary about the premature oxidation problem occurred in September of 2004 in Issue 116 of Steven Tanzer'​s International Wine Cellar, in conjunction with Mr. Tanzer'​s annual white burgundy review. Two months later, in Issue 16 of Burghound, Allen Meadows had an extended discussion of the issue. Thereafter other wine critics began to publicly acknowledge that there was in fact a problem. The initial reaction of most burgundy producers was complete denial that their wines were affected.\\ \\  Now thirteen years after the problem was first publicized, premature oxidation has clearly reached epidemic proportions. The problem clearly affects every white burgundy vintage between 1995 and 2009 (i.e. each vintage which has reached seven and a half years of age).\\ \\  For example, the results of the annual vintage tastings/​oxidation checks I have conducted each of the last nine years show the following variation in incidence of premature oxidation:​\\ \\ **1996 vintage (tasted at 10 years of age):​**\\ ​ Corked: 2/28 (7%)\\ ​ Oxidized: 5/28 (18%)\\ ​ Advanced: 3/28 (11%)\\ ​ Total advanced plus oxidized: 8/28 (29%)\\ \\ **1999 vintage:​**\\ ​ Corked: 1 or 2 of 44 (2% to 4%)\\  Oxidized: 9/44 (20%) **Highest percentage of oxidized wines ever**\\ ​ Advanced: 3/​44(7%)\\ ​ Total Oxidized + Advanced: 12/44 (27%)\\ \\ **2000 vintage (tasted at 7 and 7.5 years of age):​**\\ ​ Corked: 1/58 (2%)\\ ​ Oxidized: 9/58 (16%)\\ ​ Advanced: 7/58 (12%)\\ ​ Total Oxidized + Advanced: 16/58 (28%)\\ \\ **2001 vintage:​**\\ ​ Corked: 0/43 (0%)\\ ​ Oxidized: 4/43 (9%)\\ ​ Advanced: 7/43 (16%)\\ ​ Total Oxidized + Advanced: 11/43 (26%)\\ \\ **2002 vintage:​**\\ ​ Corked: 3/64 (5%)\\ ​ Oxidized: 5/64 (8%) or 6/64 (by my count) (9%)\\ ​ Advanced: 5/64 (8%) Tied for lowest percentage of advanced wines ever\\ ​ Total oxidized + advanced: 11/64 (17%)\\ \\ **2004 vintage:​**\\ ​ Corked: 1/63 (2%)\\ ​ Permanently Reduced: 1/63 (2%)\\ ​ Oxidized: 3/63 (5%) Lowest percentage of oxidized wines ever\\ ​ Advanced: 5/63 (8%) Tied for lowest percentage of advanced wines ever\\ ​ Total Oxidized + advanced: 8/63 (13%) **Lowest total percentage ever**\\ \\ **2005 vintage:​**\\ ​ Corked: 1/66 (2%) [Corked bottle of Raveneau MDT replaced on night one]\\ ​ Oxidized: 4/65 (6%) Second lowest percentage of oxidized wines\\ ​ Advanced:​16/​65 (25%) Highest percentage of advanced wines ever\\ ​ Total Oxidized + advanced: 20/65 (31%) **Highest total percentage ever**\\ \\ **2006 vintage:​**\\ ​ Corked: 0 or 1 of 28: 0% to 4% (includes 3 California ringers)\\ ​ Oxidized: 0/25 white burgundies (initial group consensus) or 2/25 (my late run back through all wines) 0% to 8%\\  Advanced: 3/25 white burgundies (12%)\\ ​ Total Oxidized +advanced: 5/25 (20%)\\ \\ **2007 vintage**:​\\ Corked: 1/71 (1.4%) \\ Oxidized: 3/71 (4.22%) \\ Advanced - 6/71 (8.45%) or by my count 9/71 (12.68%)\\ Total Oxidized + advanced: 9/71 12.68% (**lowest group total ever**) or 12/71 (my count) 16.9%\\ \\ **2008 vintage:​**\\ Corked: 1/70 (1.4%)\\ Other consensus defects: 2/70 (2.9%)\\ Oxidized: 3/70 (4.29%) \\ Advanced - 9/70 (12.9%) or by my count 10/70 (14.3%)\\ Total Oxidized + advanced: 12/70 (17.1%) or by my count 13/70 (18.6%)\\ \\ **2009 vintage**:​\\ ​ Corked: 0/62 (0%)\\ ​ Otherwise Chemically "​Off"​ 1/62 (1.6%)\\ ​ Oxidized: 2/62 (3.2%)\\ ​ Advanced: 6/62 (9.7%)\\ ​ Total Oxidized + advanced: 8/62 (12.9%)\\ \\ {{https://​c1.staticflickr.com/​5/​4190/​34359980502_d5e959b48f_b.jpg|external image 34359980502_d5e959b48f_b.jpg}}\\ ​ The most interesting pattern to emerge here is that **the vintages from 2002 and thereafter have a lower average combined percentage of oxidized and advanced wines than the vintages from 1996 through 2001.**. But the one really notable exception is the 2005 vintage which had the worst performance ever.\\ \\  While the problem is clearly an epidemic one, it has received scant attention in the mainstream press. There has been no serious coverage of this issue in the Wine Spectator'​s print issue and the issue was never discussed in the print version of the Wine Advocate until December of 2009. One can only speculate why. There have been articles in the London Times and Le Figaro (Paris) mentioning this wiki site, as well as mentions in a number of other newspapers and articles. This issue has slowly come to public consciousness in Europe and while most American wine collectors are quite familiar with the issue, it surprisingly remains unknown to many casual wine drinkers in the US .\\ \\   The premature oxidation problem, which began with the 1995 vintage, was not really recognized as a systemic problem until the fall of 2003, when the 1996 vintage reached seven years of age. At that time a small but discernable percentage of the wines began to exhibit premature oxidation symptoms similar to those which the 1995 vintage began exhibiting about a year earlier. When an inordinately high number of the 1995 vintage whites appeared to be partially or fully oxidized, it seemed inexplicable and people naturally sought to explain the problem as somehow related to the vintage (and there had been a considerable amount of rot in 1995). When the 1996 vintage started to show the same problems, despite being considered an ultra-clean,​ high acid and classic vintage, alarm bells started going off. Each subsequent vintage has exhibited similar problems beginning about 6.5 to 7 years after the vintage (although the vintages subsequent to 1999 have a lower incidence of outright oxidation than do 1995, 1996 and 1999, the incidence of advanced wines has been higher in a majority of the subsequent vintages.)\\ \\  The first public commentary about the premature oxidation problem occurred in September of 2004 in Issue 116 of Steven Tanzer'​s International Wine Cellar, in conjunction with Mr. Tanzer'​s annual white burgundy review. Two months later, in Issue 16 of Burghound, Allen Meadows had an extended discussion of the issue. Thereafter other wine critics began to publicly acknowledge that there was in fact a problem. The initial reaction of most burgundy producers was complete denial that their wines were affected.\\ \\  Now thirteen years after the problem was first publicized, premature oxidation has clearly reached epidemic proportions. The problem clearly affects every white burgundy vintage between 1995 and 2009 (i.e. each vintage which has reached seven and a half years of age).\\ \\  For example, the results of the annual vintage tastings/​oxidation checks I have conducted each of the last nine years show the following variation in incidence of premature oxidation:​\\ \\ **1996 vintage (tasted at 10 years of age):​**\\ ​ Corked: 2/28 (7%)\\ ​ Oxidized: 5/28 (18%)\\ ​ Advanced: 3/28 (11%)\\ ​ Total advanced plus oxidized: 8/28 (29%)\\ \\ **1999 vintage:​**\\ ​ Corked: 1 or 2 of 44 (2% to 4%)\\  Oxidized: 9/44 (20%) **Highest percentage of oxidized wines ever**\\ ​ Advanced: 3/​44(7%)\\ ​ Total Oxidized + Advanced: 12/44 (27%)\\ \\ **2000 vintage (tasted at 7 and 7.5 years of age):​**\\ ​ Corked: 1/58 (2%)\\ ​ Oxidized: 9/58 (16%)\\ ​ Advanced: 7/58 (12%)\\ ​ Total Oxidized + Advanced: 16/58 (28%)\\ \\ **2001 vintage:​**\\ ​ Corked: 0/43 (0%)\\ ​ Oxidized: 4/43 (9%)\\ ​ Advanced: 7/43 (16%)\\ ​ Total Oxidized + Advanced: 11/43 (26%)\\ \\ **2002 vintage:​**\\ ​ Corked: 3/64 (5%)\\ ​ Oxidized: 5/64 (8%) or 6/64 (by my count) (9%)\\ ​ Advanced: 5/64 (8%) Tied for lowest percentage of advanced wines ever\\ ​ Total oxidized + advanced: 11/64 (17%)\\ \\ **2004 vintage:​**\\ ​ Corked: 1/63 (2%)\\ ​ Permanently Reduced: 1/63 (2%)\\ ​ Oxidized: 3/63 (5%) Lowest percentage of oxidized wines ever\\ ​ Advanced: 5/63 (8%) Tied for lowest percentage of advanced wines ever\\ ​ Total Oxidized + advanced: 8/63 (13%) **Lowest total percentage ever**\\ \\ **2005 vintage:​**\\ ​ Corked: 1/66 (2%) [Corked bottle of Raveneau MDT replaced on night one]\\ ​ Oxidized: 4/65 (6%) Second lowest percentage of oxidized wines\\ ​ Advanced:​16/​65 (25%) Highest percentage of advanced wines ever\\ ​ Total Oxidized + advanced: 20/65 (31%) **Highest total percentage ever**\\ \\ **2006 vintage:​**\\ ​ Corked: 0 or 1 of 28: 0% to 4% (includes 3 California ringers)\\ ​ Oxidized: 0/25 white burgundies (initial group consensus) or 2/25 (my late run back through all wines) 0% to 8%\\  Advanced: 3/25 white burgundies (12%)\\ ​ Total Oxidized +advanced: 5/25 (20%)\\ \\ **2007 vintage**:​\\ Corked: 1/71 (1.4%) \\ Oxidized: 3/71 (4.22%) \\ Advanced - 6/71 (8.45%) or by my count 9/71 (12.68%)\\ Total Oxidized + advanced: 9/71 12.68% (**lowest group total ever**) or 12/71 (my count) 16.9%\\ \\ **2008 vintage:​**\\ Corked: 1/70 (1.4%)\\ Other consensus defects: 2/70 (2.9%)\\ Oxidized: 3/70 (4.29%) \\ Advanced - 9/70 (12.9%) or by my count 10/70 (14.3%)\\ Total Oxidized + advanced: 12/70 (17.1%) or by my count 13/70 (18.6%)\\ \\ **2009 vintage**:​\\ ​ Corked: 0/62 (0%)\\ ​ Otherwise Chemically "​Off"​ 1/62 (1.6%)\\ ​ Oxidized: 2/62 (3.2%)\\ ​ Advanced: 6/62 (9.7%)\\ ​ Total Oxidized + advanced: 8/62 (12.9%)\\ \\ {{https://​c1.staticflickr.com/​5/​4190/​34359980502_d5e959b48f_b.jpg|external image 34359980502_d5e959b48f_b.jpg}}\\ ​ The most interesting pattern to emerge here is that **the vintages from 2002 and thereafter have a lower average combined percentage of oxidized and advanced wines than the vintages from 1996 through 2001.**. But the one really notable exception is the 2005 vintage which had the worst performance ever.\\ \\  While the problem is clearly an epidemic one, it has received scant attention in the mainstream press. There has been no serious coverage of this issue in the Wine Spectator'​s print issue and the issue was never discussed in the print version of the Wine Advocate until December of 2009. One can only speculate why. There have been articles in the London Times and Le Figaro (Paris) mentioning this wiki site, as well as mentions in a number of other newspapers and articles. This issue has slowly come to public consciousness in Europe and while most American wine collectors are quite familiar with the issue, it surprisingly remains unknown to many casual wine drinkers in the US .\\ \\ 
 ===== Some producers are clearly more affected than others ===== ===== Some producers are clearly more affected than others =====
  • general_discussion.txt
  • Last modified: 2018/11/24 17:44
  • by roumegaire