Column Article from the May 2010 Magazine Issue
How Good Is That Wine Bag, Really?
by Tim Patterson
I’m not claiming an exact count here, but I swear that for every article or technical study published about wine flavors, two get printed about bottle closures. Natural corks, new and improved natural corks, agglomerates, DIAMs, synthetics in a rainbow of colors, screwcaps with a multitude of liners, glass caps—they all have legions of fans and detractors, most of them quite vocal, and more research money flowing their way than you can shake a pH meter at.
But when’s the last time you read something about the performance of bag-in-box (BiB) packaging? In an e-mail exchange, Sakkie Pretorius, director of the Australian Wine Research Institute (AWRI), home to path-breaking research on standard wine bottle closures, acknowledges, “BiB packaging is an orphan when it comes to peer-reviewed research publications.” Reminiscent, perhaps, of the days when screwcaps were considered too low-life for serious investigation.
- Independent technical assessments of bag-in-box packaging are rare.
- The author explains the bag types and explores technical information from a manufacturer.
- Informed winery users of bag-in-box agree they allow greater OTR rates than any glass bottle with any common closure.
- Bag films do not seem to impart flavors, but they may subtract flavors, both good ones like rose oxide and bad, like TCA.
It’s an odd omission. Box wines are a fast-growing segment of the wine marketplace, and the wine quality standard has been rising just as rapidly. In the U.S., the explosion of the premium 3-liter category has lifted the sales and reputation of box wines to somewhere near where they have been in other countries for years. This form of packaging has recently gained a lot of good press for its eco-friendliness and smaller carbon footprint. Plus, box wines go a long way toward explaining why, in the current recession, the volume of wine consumed has gone up and the dollar value has declined: The best box wines are a steal.
But how good are those bags and taps, really?
The box part of box wines, of course, has nothing to do with how well the wine keeps or the length of its useful shelf life. But the box is what consumers see and purchase, and consumers are buying a lot of them lately.
Box wines make up half or more of the volume of wine sales in Australia, Sweden and Norway, and a good 20% in not only the UK but also France. In the U.S., the category accounts for about 18% of wine sales volume. According to Information Resources Inc., the 3-liter box segment grew 19% in dollar sales during the 52 weeks ending Feb. 21, and moved 2.1 million cases (9 liters, three boxes) during that period, an 11.2% volume increase for the year.
The bump in wine quality has been striking as well, with higher-grade import labels arriving and domestic producers raising the bar. Box wines win their share of competition medals against the bottled competitions; interestingly enough, in price-graded competitions, the box wines are usually categorized at about the $20 level, the box price, not the $5 equivalent bottle price. And at least one highly decorated by Robert Parker wine comes in a box; the oracle of Monkton didn’t taste the 2003 Chateau Rollan de By from a tap, but after he gave it 90 points, Medoc vigneron Jean Guyon put 12,000 liters of it in designer boxes and did a brisk business.
Primarily, however, box wines are designed for quick, convenient consumption, not cellaring for the grandkids. Producers recommend drinking the wines within 8-12 months from the fill date (which some brands display on the packaging) and finishing the wine within a month after opening it. Distributors, retail vendors and consumers are all advised to avoid storage at high temperatures, which will damage the wines.
The previous paragraph pretty much summarizes what’s generally known about bag-in-box performance. The producers in this category, mostly industrial-scale enterprises, and the staff at Scholle, the major U.S. producer of bags and taps, certainly do their own extensive internal package testing and tasting trials, but little of that knowledge finds its way onto the public record. Some 60 international companies involved in the BiB business support an initiative known as Performance BiB, which has worked to codify standards and best practices for everything from low-friction paper in the boxes to dissolved oxygen management in the wines. The AWRI did some initial investigation of BiB packaging and oxygen exposure a few years back, and now it is launching a new round of investigations, but not much is out yet.
Meantime, we know a few things about the bags (or pouches or casks). The best factoid in all of BiB is that the concept was developed by company founder William Scholle in the late 1940s as a means of storing and transporting battery acid. Before you start cracking jokes about battery acid and box wine quality, think about all the unpleasant things that show up in bottles.
Bag film comes in several variations. The oldest form is a metalized polymer; aluminum is turned into a gaseous form, and particles are attracted to the polymer sheet. The non-reactive polymer touches the wine; the aluminum adds a much less permeable oxygen barrier. Early bags were often, in fact, bags within bags. Films have evolved to include multiple layers—either laminated one on top of another, or co-extruded in single sheets—and now also make use of ethyl vinyl alcohol (EVOH), another good oxygen stopper.
The older-style films were subject to flex cracking; if the bag was pinched or scrunched, the aluminum could crack, compromising the oxygen control. Newer materials and methods minimize or eliminate those problems. Over the years, says Lou Dambrosio, a senior vice president for production services at The Wine Group, producers of box wines in every size and at every price-point, BiB technology has steadily improved (the result of pressure from major wine producers).
Bags, however, still have a higher oxygen transfer rate (OTR) than bottles with conventional stopp
ers. A Scholle presentation from 2007, for example, indicates that the various films in its Durashield line of bags let in between .78 and .16 cubic centimeters of oxygen per square meter of surface area per day. (Tests were done in a 100% oxygen environment; normal air is only 21% oxygen.) Extrapolating here, larger-volume bags let in proportionally less oxygen because of a higher ratio of volume to surface area, in the same way that full-sized wine barrels impart less oak flavor per gallon of wine than half barrels.
Conventional closures (natural corks, synthetics, screw caps) exhibit a wide range of OTRs, but analysts agree that all of them allow in lesser amounts of oxygen than bag-in-box films. The greater permeability of bags is clearly the limiting factor on shelf life projections and practices.
Bag films do not seem to impart flavors, good or bad, or at least that’s not currently a major controversy in the BiB world. Nor are there any potential health hazards. But there is some intriguing evidence that bag liners may subtract some aromatic compounds. An AWRI experiment in 2008 spiked some Sémillon with 21 flavor compounds and then stored it in both bags (“bladders,” as the Aussies prefer) and glass ampules. Most compounds were not markedly affected. But 97% of the TDN—the chemical basis of Riesling’s petrol aromas—was absorbed within 24 hours; 35% of the rose oxide (Gewürztraminer’s lychee) and ß-ionine (violets in red wines) were eventually absorbed. On the other hand, none of the oak-aging-related compounds were affected, nor were any of the characteristic Brett aromas.
The really good news: Box bags suck up TCA, much like the plastic wrap sometimes used for home taint removal and the sheets of plastic deployed for tank-scale rehabilitation.
Oxygen is again the central issue in evaluating performance of the taps or spigots that dispense BiB wines. The great virtue of BiB packaging is that as each glass of wine gurgles out, the bag collapses accordingly, keeping the remaining wine away from air. BiBs certainly do a better job than, say, half a bottle of wine sharing space with half a bottle of air for two or three days, but they’re not perfect. Every time a little wine comes out, a little air gets in, pushing the wine on a slow glide to oxidation. The taps themselves, made of plastic, are somewhat oxygen-permeable.
Oxygen has also been an issue traditionally in filling the bags. The dominant filler technology for the past two decades has involved removing the tap from the empty bag, filling the bag, then re-inserting the tap. Even done quickly (bags fill up in a hurry) and carefully, filling has long been seen as what Dambrosio calls an “oxygen window.”
Responding to major BiB producers, taps have gotten better, too, using heavier, denser plastics that are less permeable. The leading edge of filler technology doesn’t so much “fill” a pre-existing bag but encases the wine in film from a continuous sheet, building the bag around the liquid. In the works is filling machinery that operates within a nitrogen-filled chamber, further keeping oxygen at bay.
Winemakers and other technical people I talked to from Black Box, Trinchero and The Wine Group all agreed that temperature control is a critical aspect of winemaking, filling and storage for box wines. The warmer the wines get, before and after filling, the faster they deteriorate. Producers strive to keep temperatures down in the 50°s F at filling time, and do everything they can to ensure that same temperature target for transportation and storage before sale. Filling too cool can also cause problems; the wine-chilled bags can sweat in a higher ambient temperature, creating troublesome moisture in the box.
Monitoring and managing dissolved oxygen is a clear priority. So is management of dissolved carbon dioxide; too much CO2 in a box wine exposed to heat can puff the pouch—not a good thing.
Jim Huntsinger, a vice president for production at Trinchero Family Estates, producers of the popular Cube wines sold exclusively through Target stores, says that because of the potential for oxygen exposure in the filling process, Trinchero normally adds an additional five parts per million of sulfur dioxide at filling time, a very minor variation. Trinchero also introduces nitrogen into the filling environment.
All in all, box wine winemaking doesn’t differ much from any other winemaking—at that price-point. Protocols for $200 cult wines—if anybody is still making them—are something else, but BiB packaging does not seem to require wineries to perform many biochemical tricks to suit the container.
The growth of this category of wines and the greater range and quality of the offerings within it is good news for consumers. Growth also means more incentives for continuous improvement in packaging materials, design and filling techniques. Along the way, it would be only appropriate for box wines to get their share of study and debate on everything from comparative OTR measurement to rigorous sensory trials that could track what happens during extended shelf life and after opening.
It would be especially nice to have all of this information more publicly available. And then, box wines would be orphaned no more.
For a good overview of issues involved in box wine packaging and processing, go to the Publications section of Performance BiB at b-i-b.com/bib/index.php?lang=en.