The packaging of beverages is a materials-intensive business, with steel, Al, glass, and plastics all finding a competitive niche. The cost of materials, processing, customer expectations, retention of flavor, corrosion resistance, environmental impact, etc. all enter into the decision concerning a final package. When I first heard at the Alcoa Research Lab that Al was being considered as a competitor to steel for soft drink cans, I could not believe the favorable projected economics since the cost of Al has always been several multiples of that of steel on any basis. But customer acceptance and the recycling of used beverage containers have turned the economics in favor of Al.

Of course, for many of us sophisticated adults, the packaging of soft drinks pales in importance to that of wine, our favorite health and leisure beverage. So I am again surprised that Al containers for wine are entering the marketplace. Aluminum Today magazine has announced that two Australian vineyards are marketing chardonnay, shiraz-sauvignon, and cabernet in 250 ml cans with ring-pull tabs. The can is coated on the inside with a lacquer. Some wine, and soft drinks containing citric acid, will corrode through the Al within an hour if there is a defect in the lacquer coating. Supposedly, the cans have a shelf life of five years, and are convenient when a single or two-glass serving is preferred (not my own preference). The suppliers argue that the Al can eliminates wine spoilage from oxidation and cork taint, avoiding the need for additive preservatives. The light weight and compact shape keeps shipping costs down relative to glass bottles. At the same time as the Al can is replacing the glass bottle, the Al bottle is threatening to replace the Al can. The impact-extruded Al bottle with a neck and screwcap seal would then suit more hearty consumers. A US winemaker is providing Al screwcaps for wine in glass bottles, wine intended for drinking within six months. The ‘boxes’ containing wine in polymer bags have also improved so that better wines are being packaged in this way, but are still not suited for long-term storage.

The competition in wine-packaging materials does not stop with choosing the container. Traditional natural corks are being substituted by composite and polymer plugs, driven by the increasing cost and decreasing supply from Spain's cork trees. But do the pretenders fulfill the preservation requirements for corks for fine wines? I don't know. In the early 1990s, it was announced that Pb would have to be removed from the closure caps on top of glass bottles. Two replacement materials were considered: Sn and a laminate of Al and a polymer. Because of its cost, Sn closure caps are reserved for expensive wines, liquors, and champagne. To realize the production of a Sn cap, the existing Pb processing sequence of continuous roll casting/cold rolling/stamping/paint baking at 140°C has to be modified. The wrinkle-free stamping requires a lengthwise indentation that always results in tearing upon opening (a particular tax requirement). Likewise, the Sn cap supports a perfect cut when subjected to the knife of the wine waiter, and a soft feel (equivalent to Pb) for the sophisticated diner. The recrystallization of Sn poses a potential problem, because unalloyed Sn forms large grains at the baking stage, negating a reliable tearing upon opening. In fact, subtle addition elements to Sn guarantee fine grain recrystallization and wrinkle-free stamping. Nevertheless, most low-prestige closure caps are made from Al and polymer, so the consumer will have to overlook the unavoidable wrinkles.

As a further ‘scientific’ nuance to wine making, I read that winemakers at the Estevez vineyard in southern Spain are playing music to the casks of sherry in storage. The researchers want to know if the yeast used to age sherry grows better with music loosely based on its own DNA. A piano-playing microbiologist at a Madrid hospital has transformed its genetic code into music by arbitrarily assigning tones from the do-re-mi scale to the four building blocks of DNA's double helix. It is too early for a firm verdict, but there are hints (so I read) that the yeast cells floating to the top of the wine casks to cushion against the damaging effects of air seem to be more organized. If the yeast cells that turn sugar into alcohol are affected by external factors such as temperature and humidity, and the cells are just as alive as musically vulnerable humans, might not the music keep the yeast happy and productive? Personally, I could use un verre de bon vin rouge!

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DOI: 10.1016/S1369-7021(05)00720-0