Grapevine & Wine 02/08/2010

How to preserve wine to the best of one’s ability? It depends on the cork and on the bottle

Directions to follow not only with maturation wines. With longer stays in the cellars and on the shelves the aromatic features need to be better preserved

Corks and bottles have long been overlooked, as a heavy bottle was more a sign of prestige rather than something with a functional purpose, and the choice of the color was based on purely esthetical criteria. Same for corks. A bottle with an excellent cork gave an idea of prestige, and the cork smell that affects about 5% of bottles gave a commercial and marketing boost to synthetic corks that nowadays are rather common, mainly for white wines.
The need for a longer preservation in cellars or on shelves of even young and fresh wines, ready to drink has been motivating producers to be more careful about the quality of materials, in order to safeguard the aromatic and organoleptic features of wines for as long as possible.

No more cork smell even with corks
Before its removal from an oak bark, or during its manufacturing, the cork can acquire microbiological substances that cause unpleasant, mould-like and humidity smells. The main responsible for this is the fungus Trichoderma longibrachiatum. The institute for the vine and wine of Ponferrada, Spain, identified the gene responsible for this bad small. One of authors of this research, Juan José Rubio Coque, explained that the goal for the future should be “to obtain fungi genetically modified in order to remove this gene and able to grow on cork and, after being artificially inoculated in the cork during the manufacture phase, to prevent non genetically modified Trichoderma longibrachiatum from developing”.

Long-lasting sensations of green and vegetable
The 3-alchil-2-metossipirazine (MPs) are smelling compounds derived from grapes and insects, which are responsible for the sensations of green and vegetable in wines. More compounds, like acetate esters, contribute too. The preservation also needs to take into consideration the content in phenols and the oxidative phenomena.
Several factors, including the bottle color, affect these parameters.
Experimental preservation conditions:
- at room temperature (22 °C, 72 °F) with fluorescent light
- at room temperature in the dark
- at cellar temperature (12 °C, 54 °F) in the dark
- light, green and amber bottles

MPs do not vary consistently over time and in the specified light and temperature conditions. Acetate esters decrease in time, independently of light and temperature, while phenylacetate and isoamyl acetate decrease more at 22°C than at 12°C.
In the dark more SO2, either free or bound, is retained, and its concentration is affected by the bottle color. The phenols and the oxidations are influenced both by the bottle color and by the temperature.

di Ernesto Vania