Using balled-up plastic wrap to ameliorate the funk of a corked bottle (because TCA adsorbs, or clings, to the cling wrap) is an old trick, but I’d hazard that our thoughts about wine and plastic didn’t go much further until the recent hullaballoo over BPA and the health risks it poses when it leaches out of packaging and into food. We’re newly aware, now, that plastics aren’t just neutral, inert, ignorable containers. The good news is that Scholle, the major manufacturer of the plastic bags inside box wine, asserts that their bags are BPA-free; more on that note here, a piece on wine safety I wrote for Palate Press.
But the wine safety coin has two sides: your safety, and the wine’s safety. Is the wine safe from the bag? “Scalping” is a known problem with plastics. Like people who can’t swim clinging onto the edge of a pool, hydrophobic (“water-fearing”) molecules decide that they like the plastic better than the nearly-all-water environment of the wine, and they hold on. With those molecules attached to the plastic instead of suspended in the wine, the wine’s flavor changes for the worse.
We know almost nothing about the specifics of what wine components end up attached to the plastic,** but several studies over the past few years have compared the composition of the same wine stored in different packaging systems for several months. Just out in the past few weeks is research showing that Vilana (a white varietal wine made in Crete, chosen because the researchers are from Crete) is perceptibly different, compared with the gold standard dark green glass bottle, after three months of bag-in-box storage. SO2 values were significantly lower after just a month in plastic, and low enough to signify a significant threat of white wine oxidation after two months. Titratable acidity increased significantly after two months, and a whole slew of volatile (aromatic) compounds decreased by a more or less significant degree.
Regrettably, these folks didn’t assess what effect those changes had, if any, on wine flavor; they only asked their tasters whether the bagged wine was different than the bottled wine (which it was) and not how it was different or whether it was more or less tasty.
Similar problems with bag-in-box Chardonnay were demonstrated by Hildegarde Heymann and her team at UC Davis last year, showing decreased volatiles and increased oxidation products with bagged wine, especially bagged wine stored at warm or hot temperatures. Individual wines are bound to be affected by bagging to different degrees: the most important flavor characteristics of Riesling will depend on a different set of molecules than those for Chardonnay or Vilana or Tempranillo. But it’s still safe to say that flavor scalping is an all-around problem for wines stored in plastic, and that bags leave wine dangerously susceptible to oxidation if left to sit around for a few months.
Most bag-in-box wine is purchased for immediate or near-immediate consumption, as is most wine in general in the United States. But, in every case, undesirable bag-related changes were accelerated by high temperatures. Between unrefrigerated shipping conditions and potentially careless in-store handling, I suspect that stores and wines with lower turn-over rates often don’t taste the way they should by the time they reach someone’s glass.
If we’re talking about the cheap stuff that goes into most boxed wine, and the (I’m going to be blunt) undiscriminating people who drink it, that’s inconsequential. But the push for better wine in “alternative” packaging (essentially all of which involves plastic, with the exception of refillable growlers) has been un-ignorable. This is great: solutions like bagged wine are generally more environmentally friendly, lower-cost, and super-sensible for someone (like me) who wants to have one glass of respectable wine a night (and who hasn’t yet sprung for a Coravin, which I’ll grant is the obvious and better solution). But the plastic system — or control over storage conditions, or preferably both — will have to improve before an educated consumer will want to entrust anything other than a casual backyard red to a plastic bag.
**I suspect that the companies who produce and sell bag-in-box wine actually have a lot of privately-generated data about wine-plastic interactions, but they’re not sharing.
The Wine-o-scope 