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What properties of grapes make them so suited to wine production?

What properties of grapes make them so suited to wine production in comparison to other fruits?

While a wine-like beverage can be made using virtually any fruit, the grape is particularly suited for two main reasons. One is sugar content. Grapes have a higher amount of fermentable glucose and fructose than most fruits. Most other fruits, when used to produce a wine, require supplemental sugar. The second important element is low acidity. Most fruits are too tart, largely from citric acid, and must be diluted to produce a wine that is not overwhelmed by acid. Grapes are less so, and derive their acidity from tartaric acid, an unusual acid that is more resistant to bacteria.

What is the distinction between Syrah and Shiraz? What about Petite Sirah?

In fact, there is no difference between Syrah and Shiraz grapes, as they are the same variety. Syrah is the grape used for France’s famous Hermitage wines, a variety introduced to the United States only recently. Shiraz is simply the Australian name for the same grape, derived from an older name for the grape, Scyras, which was in use when the grape was introduced to Australia. In spite of identical grapes, the Australians produce Shiraz wine in a distinct style from other Syrah producers, such that some non-Australian vintners will now label wines made with this grape as Shiraz, in order to denote a similar style to Australian Shiraz.

Petite Sirah is another story. The Petite Sirah grape has a mysterious origin, but is possibly derived from the unusual French variety, Durif, a cross of Syrah with another variety, Peloursin. Thus, while Syrah may be one of the parents of Petite Sirah, the offspring is quite distinct from the parent, and the wines created from the Petite Sirah grape are quite distinct from Syrah.

Why do some vintners refrigerate wine below freezing before bottling?

Many vintners refrigerate wine to between 14° and 24° F for several weeks, just prior to bottling. This is done to stabilize the wines against tartrate precipitation, which is the formation of crystals of tartaric acid in the wine bottle, which would otherwise occur as the wine ferments. These crystals are harmless, readily dissolving in the mouth, and do not affect the flavor of the wine. However, the crystals can easily be mistaken as shards of broken glass by those unfamiliar with tartrates. In order to avoid this confusion, the wine is cooled in a tank so that all the tartrates are precipitated before bottling.

Incidentally, wineries do make use of the remaining tartrate crystals. Wineries are the only source of tartrates, which are used in non-alcoholic drinks and foods, as well as cream of tartar. So the crystals are regularly removed from the fermentation vessels in order to be purified and sold for these purposes.

Originally published in our Gold Wine Club's The Wine Press, Trentadue Winery edition featured in 2005.