More or less, each of us has an idea about what “shelf life” means for a food product: It’s “the length of time that a commodity may be stored without becoming unfit for use, consumption, or sale” (Wikipedia). Does this definition also apply to wine? After all, no wine label bears the words “best if consumed before…”—yet. Actually, though, shelf life is a notion that affects every kind of wine, from the fresh ones to the most aged ones because, as Vinventions researcher Stéphane Vidal says, it “is about having the right product at the right moment” and is apparently something of interest for all wine producers.
That’s why the Department of Biotechnologies at the University of Verona recently organized a conference about shelf life in the wine world, with the collaboration of Assoenologi (the Italian Association of Oenologists) and Nomacorc, the renowned leader for wine closures and now a member of Vinventions.
“Any wine has its own shelf life, so our starting point must be the features of the wine itself,” notes Vidal. “After that, we have to worry about the evolution we want the wine to have to get the best experience for the consumer: a constant pleasure in tasting.” With this, we can never forget that time is a crucial factor in the process, and has its own influence.
That said, how can you manage the shelf life?
“You have to be able to measure the oxygen in the wine, managing the reduction risks and, of course, your wine needs to have the proper amount of polyphenols,” states Vidal. Easy to say, a bit less to do. Each grape is, in fact, a “world apart” and its polyphenols, the main actors in the phenomena of reduction or oxidation that affect the “wine time,” are just one of the most important keys to this. If you can measure them in real-time, you’ll be able to control and predict the shelf life itself.
“Managing the shelf life means that when the final consumer uncorks that bottle, the wine won’t be oxidized or reduced,” says Christine Pascal, another researcher with Vinventions. “The wine will evolve, but without going into the two ‘risk groups’ of oxidation or reduction.” Again, a lot depends on the grape itself: We have to figure out how many precursors of oxidation or reduction our wine might have according to the grape variety. “Measuring these polyphenols will allow us to understand the duration of the shelf life,” she explains.
Doing that analysis takes time and is a complex and expensive issue; however, now, thanks to a new Vinventions technology (PolyScan from the Wine Quality Solutions group), it is becoming easier, and so is the management of polyphenols in real time.
At the same time, though, demonizing the oxygen would be a mistake, as Angelita Gambuti (University “Federico II” of Naples) explains: “There are very tannic red wines that need oxygen to improve. The issue is that the process goes on and on,” and the switch from improvement to oxidation becomes only a matter of time. There are several solutions to that problem, but the simplest one is also affordable for every cellar: choosing a closure with a controlled permeability. And speaking of that, what happens to a wine sealed with a screw cap? Its critics often complain about the “flavor of reduction” the wine might have; worried by this possibility, the oenologists often add a bit of copper (the authorized quantity is max. 1 mg/liter), before bottling, as a preventive measure. “Too bad that copper kills a lot of freshness flavors even before any reduction problem occurs,” adds Maurizio Ugliano, enology professor at the University of Verona. “Furthermore, in some cases it has been observed that the presence of copper increases the problems, rather than eliminate them.”
Conclusions? The wine producer who wants to predict the evolution of the wine has to worry about three things: the oxygen dissolved in the wine itself, that oxygen in the “bottle headspace” (i.e. the space that exists between the wine and the closure) and the permeability of the closure. Most of the time there is more oxygen in the headspace than dissolved in the wine—the same “variance of bottles” depends more on this element than on the quality of the closure.
The most important thing to remember is that, on average, the TPO (Total Package Oxygen, the total amount of oxygen present in a bottle), can compromise a few years of aging already starting from the first day of bottling. Moreover, selecting the most suitable closure for the expected shelf life will allow each wine to evolve in the way the winemaker intended.
This piece was first published on Vinix.com in Italian.