This year Wine Business Monthly's Closure Survey Report highlights some of the trends in wine closure usage as well as issues relating to oxygen transmission. We find that while there is disagreement among winemakers on the importance of oxygen transmission through the closure, there is widespread agreement on the importance of consistent transmission and on the importance of matching the closure with the winemaking process.

Another finding of this year's survey is that natural cork's slight decline in usage in recent years, due to the rise and popularity of other closures (such as screw caps), appears to have leveled off somewhat. Between this trend and screw cap's cooling a bit (after a few years of very strong growth), we see a greater variety and a more even distribution of closures being used in today's market, especially with larger wineries that produce a wide range of products at many price points.

Oxygen Transmission

This is the second year we have surveyed respondents about oxygen transmission through the closure into the bottle (the first survey was in 2006, revisiting every other year). The importance of oxygen ingress through the closure after bottling has been a much debated aspect of closure performance, with opinions differing widely as to the need for, correct amount of and consistency of oxygen transmission.

Chart 1 - Click to enlarge.

Chart 2 - Click to enlarge.

Chart 3 - Click to enlarge.

Chart 4 - Click to enlarge.

Chart 5 - Click to enlarge.

Chart 6 - Click to enlarge.

Chart 7 - Click to enlarge.

Chart 8 - Click to enlarge.

Chart 9 - Click to enlarge.

While many agree that traditional cork's ability to let small amounts of oxygen in over time is favorable for wines that need more aging, many also agree that there has not been ample time to determine the effects of newer closures in regard to oxygen transmission and wine character. Risking spoilage via the transmission of large amounts of oxygen has many winemakers today opting for screw caps, which were ranked highest this year for being the most consistent closure in terms of oxygen transmission (in this case, rarely allowing transmission; see Chart 1).

Opinions were very mixed on how important oxygen (entering through the closure) is to in-bottle wine development (Chart 2). Forty-three percent of respondents (ratings of 4 and 5) thought that having some oxygen transmission through the closure was important while 33 percent (ratings of 1 and 2) felt it was not very important. This year's results closely reflect those of our 2006 report.

"I don't believe that oxygen entering through the closure is that important," said Kenneth Albert, winemaker at Shelburne Vineyard (Shelburne, Vermont; 2,000 annual cases). "Our wines are best consumed relatively young, so they are not aged for an extended time."

Richard Arrowood, director of winemaking and winemaster for Arrowood Vineyards & Winery in Glen Ellen, California (25,000 cases), feels that the oxygen entering through the closure is very important to wine development. "A controlled oxygen process is important, especially for red wines that you're going to be laying down for a long time," he said. "For Sauvignon Blanc or Rosé this isn't as important, or even desirable, since you want these wines to taste fresh and young."

Winemakers were much more definitive on the importance of consistency in the amount of oxygen transmitted into their wine bottles (via natural cork, technical cork, synthetic closures and screw caps). Just over half of all respondents (54 percent) indicated that uniformity in oxygen transmission from bottle to bottle is "very important," with only 3 percent indicating that it was "not important" (Chart 3).

"We only use natural cork, so having a great deal of consistency, as far as not allowing too much oxygen into the wine, is very important," said Arrowood, noting that while changes in temperature will naturally occur, as long as they don't fluctuate too much, consistency of oxygen ingress can be well maintained.

Winemakers also were emphatic about the importance of matching up the intended closure with the winemaking process. Two-thirds of respondents indicated it was important while only 20 percent said it was not important (Chart 4). This year's results were similar to responses we received in 2006.

The importance of matching the intended closure with the winemaking process varied by size of winery. Larger wineries (500,000 cases and more) felt most strongly that matching the intended closure to the winemaking process was very important: 78 percent of large wineries felt this way, compared to 53 percent for mid-size wineries (50,000-499,000 annual cases) and 34 percent for small wineries (up to 49,000 annual cases).

Winemakers at MacLeod Family Vineyards, in Kenwood, California (1,200 annual cases) feel that matching up the closure with the winemaking process takes a backseat to packaging and the concept of quality and tradition. "With wine, you're buying on 90 percent perceived value, so we buy tin capsules and the very best natural corks we can find," said George MacLeod. "Tradition is in line with what people expect from quality wine."

Using different types of closures also obviously affects the amount of oxygen transmitted into a wine bottle, so we asked respondents to rate on a five-point scale each of the most popular closure types (natural cork, technical cork, synthetic closures and screw caps) as to whether they had a low transmission rate (rating of 1) or a high transmission rate (rating of 5). Corks ranked as having the highest transmission (3.1), followed by synthetic closures (2.8), technical cork (2.7) and screw cap (1.4) (Chart 5).

Walla Walla, Washington's Lowden Hills Winery (1,200 cases) only uses natural cork because of its ability to breathe. "I buy into the thought that over the years cork will allow the wine to age better than a synthetic, due to the oxygen it lets in," said owner and winemaker Jim Henderson. "The amount of oxygen transmitted over, say, a year, wouldn't have such a dramatic effect, but over time it certainly can."

Aaron Lieberman, winemaker for Cottonwood Winery of Oregon in Salem (2,000 cases), also uses only natural corks. "We use it for the aesthetic component; but also synthetic closures and screw caps are still not a proven enough technology for me at this point," he said. "I've seen some oxygen transmission problems with screw caps if they are not just right and with synthetics not allowing red wine to age properly." For winemakers using oxidation as a winemaking tool, learning from their supplier and knowing exactly how different types of closures transmit oxygen is an important key to developing unique and individually styled wines.

As far as rating each closure type's consistency of oxygen transmission (1 being inconsistent and 5 very consistent), screw caps rule the day, earning a high rating of 4, followed by synthetic (3.3), technical (3.1) and natural cork (2.8) (Chart 6).

"Natural cork has the highest amount of variation, depending on what you buy and the quality," said David De Sante of De Sante Wines (3,500 cases) in St. Helena, California. "The good thing about our industry is that corks are pretty well understood; we have less experience with other closure types."

Interestingly, although consistency is highly rated by winemakers year after year, natural cork still remains the most widely used closure (80 percent of all responding wineries use natural cork on their 750 ml bottles). Despite the desirability of consistency, factors such as customer perception and closure performance over time appear to be of higher priority.

We also asked respondents to rate the four closure types on the prevention of unwanted oxidation in storage (1 being excessively bad at preventing unwanted oxidation and 5 being very good). Wine can become oxidized when exposed to air, causing an undesirable off-odor and a brown tint. It is generally accepted that screw caps are best at preventing excessive oxidation.

This year's survey results showed that in regard to preventing oxidation, screw caps did indeed lead with the highest rating (4.3) for being very good at preventing unwanted oxidation while in storage (Chart 7). Synthetic, technical and natural closures all rated similarly (around 3) relative to preventing unwanted oxidation.

We also asked respondents to rate the four closure types on the prevention of unwanted reduction while in storage (1 being very bad at preventing unwanted reduction and 5 being very good). Unwanted reduction can occur when a wine has been deprived of oxygen in the bottle (reduction can also be said to be the opposite of oxidation: reduction is the gaining of electrons, and oxidation is the loss of electrons).

Natural cork led with the highest rating (3.8) for being able to prevent unwanted reduction while in storage, followed by technical (3.4), synthetic (3.2) and screw cap (2.7) (Chart 8). In comparing results from 2006, there has been little fluctuation among technical and synthetics in this regard, but we find that respondents rated natural cork higher this year (for its ability to prevent unwanted reduction) and screw caps substantially lower.

"While wine develops more with the presence of oxygen, it can just sit there and turn in on itself the more you deprive it," said De Sante, who notes that a wine with a reductive quality can often taste like chive, onions or burnt rubber. "If you're using cork, however, the wine can emerge from this state; but if you're using another closure, it can get worse."

Reduction, however, also takes place during the entire winemaking process. According to Richard Arrowood, "In addition to when the wine is bottled, reduction is also occurring when the grapes are being processed and during barrel aging. However, hopefully by the time the wine reaches bottling, it is fairly stable."

Closure Usage Patterns

When looking at the ratio of different closure types used in bottling red and while wines (in 750ml bottles), overall, natural cork is still the clear leader for both: 65 percent of reds and 45 percent of whites are sealed with natural cork (Chart 9). Among the remaining three closure types, usage is fairly evenly divided. In the last three years, there have been no sweeping changes; however, while use of natural cork and screw caps has decreased slightly (natural cork partly due to increasing prices of European materials and screw caps due to passing their "something new" stage), the use of synthetic closures and technical corks has increased slightly.

Chart 10 - Click to enlarge

Not surprisingly, the ratio of closure types used for red and white wines differs considerably depending on winery size: small wineries (which generally charge higher prices and are more image-conscious) use natural cork much more often (red: 68 percent, white: 49 percent) than mid-size wineries (red: 55 percent, white: 35 percent) and large wineries (red: 35 percent, white: 15 percent). Overall, larger wineries use a higher ratio of screw caps, technical corks and synthetic closures due to their low cost and suitability for lower-priced wines.

Shelburne Vineyard uses 75 percent natural cork and 25 percent technical cork on its 2,000 cases of wine. "The reason we primarily use cork is that we are a small winery trying to establish ourselves, and cork presents a quality image to the public," said winemaker Ken Albert. "Screw caps would work fine, too, but for us it's just the wrong image for us; Plump Jack can get away with it, but we can't."

David De Sante has chosen to forgo screw caps for now because of storage concerns. "Screw caps are not load-bearing and are not designed to be stacked more than three pallets high, at which point they start to buckle," he said. "Until they say I can stack them five or six pallets high, I won't go there."

While the closure that a wine is sealed with is most commonly tied to price--natural corks are used at higher price points while synthetic, technical and screw caps are used at lower price points--we can see some subtle yet important shifts over the last five years of data when looking at which closure types wineries use at different price points (Chart 10).

At the under $7 price point, there is no clear leader among the four most popular closure types; however, synthetic and technical are still used most often, due to their low cost, followed closely by natural cork and then screw caps.

At the $7-$10 price point, we see a similar overall ranking as with the lower price point; however, natural cork and synthetic are down slightly this year, along with screw caps. Screw caps show the largest change at this price point, dropping in usage by 8 percent since 2007, an abrupt turn from the previous years of steadily increasing usage.

At the $10-$14 price point, we see a leveling off somewhat of all closure types used, driven by natural cork's decrease and screw cap's increase over recent years. As is common, over the course of the past four years we see synthetic closures and technical cork jockeying for the two middle positions at this price point.

Unlike the slight erosion of natural cork usage at the lower price points, we find it holding its own at the upper price points, with 71 percent of wines at the $14-$25 price point being sealed with natural cork. The remaining three closure types are used much less frequently at this price point, but among them, in similar ratios.

At the highest price point, over $25, there has been little change in closure usage over the past five years: natural cork remains the most preferred closure in this category; it has given way to only a slight increase in technical cork and screw caps.

The unique path each winemaker takes to achieve their goals reflects the many ways great wine can be created, whether it includes purposely inviting oxygen in or keeping it out via the chosen closure, or favoring a certain closure type that complements their winemaking style. As closures continue to improve in quality and increase in variety, many winemakers will continue to experiment in their search for ultimate wine quality and character--or, for others, simply a good solid wine at a reasonable price. wbm

Respondents by Winery Size - Click to enlarge

Respondents' Job Functions - Click to enlarge

Survey Background

Wine Business Monthly's 2008 Closure Survey consisted of 14 questions related to oxygen transmission, oxidation and reduction, ratio of closure usage and usage by price point. Closures were defined for this survey as natural corks, technical corks (1+1, 2+2, agglomerate, composite cork, etc.), synthetic closures (100 percent plastic, extruded or molded) and screw caps.

Results were tabulated based on the size of responding wineries. Respondents included 242 wineries from across the U.S. and abroad, notably: 114 from California, 28 from Washington, 20 from Oregon, 9 from Virginia and 8 from New York. Eight of the respondents were from Canada, and an additional 6 were from elsewhere outside the U.S.

Respondents to the survey overwhelmingly were small wineries: 82 percent of the wineries that responded were small (fewer than 50,000 cases), 14 percent were mid-size (50,000-499,999 cases) and 4 percent were large (500,000+ cases).

Seventy-eight percent indicated their function as winemaking, 57 percent listed their function as president/owner/GM while 34 percent of the respondents indicated cellar/production. Other respondent functions included sales/marketing (28 percent), tasting room (17 percent), vineyard management/viticulture (29 percent), purchasing/finance (33 percent) and other (8 percent). Respondents could choose more than one function.

Cathy Fisher lives in Sonoma and has been writing on the wine industry for four years.