Tasting the Effects of Wine Closures

Conference examines sensory effects of natural corks, screwcaps, synthetics

by Andrew Adams
These wines bottled with natural corks showed a larger disparity in color due to cork’s wider range of oxygen transmission. Source: UC Davis

Napa, Calif.—The recent Wines & Vines Packaging Conference featured two tastings that showed how closure choice can affect wine quality.

The first tasting, sponsored by Guala Closures, took place in the morning and featured wines by CADE Winery in Napa Valley. CADE is part of the PlumpJack Group, and John Conover, general manager of PumpJack Winery and partner in CADE, said the company had been open to alternative closures because the founding partners saw first-hand how unpleasant a corked wine was for customers of the original PlumpJack Wine & Spirits shop in San Francisco, Calif. He said that experience helped motivate the company’s willingness to bottle its estate wines under screwcap as well as participate in a study on closures with the University of California, Davis.

Both sessions, held in the demonstration kitchen of the former Copia building in Napa, Calif., drew a full crowd of 75 people. The tastings were conducted with Rastal glassware from Germany, provided by conference sponsor Chrislan Ceramics.

Dr. Anita Oberholster, cooperative extension specialist in enology for UC Davis, provided an overview of the research project that is being headed up by Dr. Andrew Waterhouse as well as some early conclusions. “The first question the research is attempting to answer is whether variability using a specific closure is large enough that a consumer can taste the difference,” Oberholster said.

Collaborative closure study
PlumpJack and UC Davis arranged to have 200 bottles of the 2011 CADE Sauvignon Blanc bottled with an Amorim natural cork, Nomacorc Select 300 synthetic cork or Amcor Saranex screwcap, for a total of 600 bottles in the study. The rate of oxidation was observed through color darkening (or color absorbance) over time as measured by a spectrophotometer, with each bottle acting as its own control. Using each bottle as a data point, the researchers were able to create a slope based on the observed OTR.

Based on the study, screwcaps appear to offer the most consistent OTR, followed by synthetic corks. The greatest variation came from natural corks. Oberholster said getting a better understanding of closure variability should help winemakers make informed decisions at bottling to ensure wines conform to a specific style.

While the screwcap and synthetic closures did a better job of preserving the wine as it tasted at bottling, natural corks added “more aging character,” which resulted in a more complex wine. Depending on the wine or winemaker, this aged character could be a desirable trait.

“At the end it is also about helping the winemaker to make informed decisions based on objective data,” Oberholster said. “We are currently planning the sensory testing, so the answer to the key question has yet to be answered.”

Preserving versus aging
The PlumpJack team including CADE winemaker Danielle Cyrot brought bottles of the Sauvignon Blanc that is part of the UC Davis study as well as its 2008 CADE Howell Mountain Cabernet Sauvignon, which was bottled under screwcap and natural cork. The tasting was conducted blind, and Cyrot gauged the opinion of those in the audience. The greatest variation in taste came between the synthetic corks and screwcap versus the natural cork, which almost tasted like a different wine.

Cyrot described the Sauvignon Blanc bottled with natural cork as exhibiting more pear, melon, honey and cantaloupe with less acidity and being a bit more rounded, softer and showing more of the oak. The synthetic cork and screwcap wines were both “fresh, flinty, floral” in Cyrot’s opinion, but had slightly different fruit flavors. “Basically, I thought the synthetic and screwcap closures performed best at preserving some of the aromas and flavors I was trying to capture in the bottle,” she said. “They both tasted more like the day the wine was bottled.”

The cork-sealed wine tasted the most different to Cyrot, and this appeared to be the consensus of those in the audience as well. “The cork closure stood out as most different, but not necessarily in a bad way,” she said. “It was just more aged.… I felt the closure had played a role in stylistically changing the wine.”

The Cabernet Sauvignons tasted relatively similar, and when Cyrot asked the audience to raise their hands to indicate preference, the room was about evenly split between the two.

Cyrot said she still needs more time to understand what type of closure is best for CADE’s reds. “I am making sure that the tannin structure and mouthfeel are balanced before putting the wine in bottle. The wine still tastes like Howell Mountain, but hopefully the tannin structure isn’t a grippy, hard, undrinkable kind of tannin,” she said. “So I want a closure that will preserve the fruit aromatics without overly oxidizing the wine.”

Screwcap options
Later in the day, Doug Fletcher the vice president of winemaking for the Terlato Wine Group, presented wines from his own trial on different screwcaps. The tasting was sponsored by Mala Closures and featured a 2012 Pinot Grigio bottled in February 2013 under five VinPerfect closures with different oxygen transmission rates, a Saranex lined closure and one with Saran-tin.

The bottles with the lowest OTRs had some sensory attributes of reduction as well as a lean texture. On the other end of the oxygen-transmission spectrum, the wines were rounder and more fully developed. Fletcher’s preference, which was also the preference of those in the audience, was for the wines bottled with a closure offering a mid-range OTR.

He said he used a screwcap with a Saranex liner for the trial wine's commercial release because at the time he knew it resulted in less reduction issues than the Saran-tin liner. He later opted to use the VinPerfect liners because they provided a more consistent OTR, and wines sealed with the VinPerfect Medium were among those preferred by the audience at the tasting session. Fletcher said the trial was to see what OTR level works for each wine and he said he’s still not sure what the answer is.

While he thought wines bottled under closures with higher rate OTRs would have browned or gone oxidative, Fletcher said they have held up quite well. In light of what he’s learning through the study, Fletcher said he thinks less sulfur dioxide could be used in the cellar in tandem with a nitrogen-drip system on the bottling line. He said he also has more confidence in the stability of wines with higher OTR closures—at least for the short term.

(Editor's Note: This story was updated on Sept. 11, 2014 to clarify Doug Fletcher's choice of closures.)

Posted on 09.09.2014 - 11:14:54 PST
It would be useful to define acronyms before using them. I was left trying to figure out what OTR meant. I assume it is oxygen transmission rate. However, the coloring of the wine is a secondary effect of the oxygen transmission. Better to use the technology whereby you can remove contents of the gas in the header without removing the closure.

Posted on 09.09.2014 - 11:35:13 PST
What about glass closures (vinolok)? I always see this debate going on and glass is never mentioned........

Posted on 09.09.2014 - 14:46:59 PST
What I have found in the past between the type of closures is this. A) Screwcap, best used, as described above, to retain the freshness of the wine, in particular whites, that are made to be drunk young. B) Cork, for reds, that need time and a bit of O2 help to mature, soften the acids and tannins of big reds. C) Synthetics, the wines inbetween.

Posted on 09.10.2014 - 17:37:00 PST
In addition to oxidation of somee of the SO2, post-bottling chemical changes are a continuation of the slow acid hydrolysis of saccharides and glycosides. A cork has an internal surface area of some 2-3 square metres and a significant capacity for the adsorption of volatile substances (including sulfides). After a couple of years under cork, wines tend to become 'softer' and more mellow.

Posted on 09.09.2014 - 19:24:23 PST
I agree with the 14:46 post. I have switched to screwcap on most of my whites, but continue to use higher end cork for my reds. That said you do need to watch for screwcap reduction on whites. I have/will conducted a similar trial with Red Mountain, WA Zinfandel for 4 vintages (2010-2013). Thus far the cork closure wines have been preferred by most because they are much softer, rounder and all round more developed. Those that prefer the screw cap wines tend to like younger style wines(fruitier, drier, more angular wines). 2010 I used Tin, versus 2011/12 Saranex, and 2010 under tin is still like it was bottled yesterday. The Saranex closures seem to be showing some maturing but still too early to tell, however nowhere near the cork. 2013 will likely go under cork versus the new O7 product.
Chris Baker

Posted on 01.09.2015 - 20:22:22 PST
I am a few months behind on reading so I was happy to see what I have known since I started bottling all my wines including a 10 month aged Cabernet in screwcap, back in 2003. I ask the question: Do winemakers want their wines to age as long as possible? I think the answer would be scewcap closures, but of course if you want your wines to age faster, it would be cork.
David Coffaro