Beat the Banana
While reading this column, warmly clad in your flannel pajamas with mug of coffee in hand, have a thought for the hundreds of us shivering in our running gear while waiting for the great yellow banana to appear in Kowloon. This whacky charity race, organized to support the World Wine Cancer Research Fund, involves chasing a fleet-footed volunteer clad in a banana suit through the streets of Tsim Sha Tsui. When it comes to wine, banana sends winemakers scampering in the opposite direction. Though not technically considered a wine defect or fault, banana aromas are generally the sign of a simplistic and short-lived wine.
Banana-like aromas appear in wine when grapes are fermented at excessively cool temperatures. Just as a chef monitors cooking temperature, a winemaker must pay considerable attention to fermentation temperature. There are as many views regarding ideal temperatures as there are banana trees in Southeast Asia, but white wines are fermented at about 10-20° centigrade, whereas red wines are fermented at warmer temperatures, say 20-32° centigrade. Fermentation temperatures vary by grape variety, grape color, weather, and winemaker style.
When yeasts gorge on grape sugars they are converted into alcohol. While feasting on the sugars, the little yeasts emanate heat. As the juice in the tanks or barrels gets warmer, the yeasts eat even faster, which generates yet more heat. The higher the sugar levels in the juice, the feast gets even more frenzied – and the temperature warmer.
If a winemaker is producing a red wine, a little heat in the tank is helpful as it aids in extracting red color from the grape skins. Too warm, however, and the wine will taste like cooked fruit, or jammy. White grapes are even more sensitive to heat than red grapes, so winemakers keep white wine fermentation vessels even cooler during fermentation. Cooling the tanks slows the fermentation and results in more complex and interesting fruit flavors in the wine. That is why many tanks at wineries have “cooling jackets” or on a warm sunny day during vintage you might see winery staff spraying the outside of a tank with cool water. Some eager bananas cool their tanks to such a low temperature level that the wine develops what is disparagingly described as “juju candy,” “tutti-frutti,” and confectionary character or – you got it – banana nose.
Not all wine drinkers find banana-like aromas unappealing. Georges du Boeuf, a French producer famed for his successful Beaujolais wines, deliberately uses a yeast strain that exaggerates the banana-like aromas that emanate from his popular everyday drinking wines. And, of course, wine can be made from any fruit, including bananas. Having tried a few banana wines over the years, I would recommend that if someone hands you a glass of banana wine – or a grape wine smelling of banana – hand your glass to the nearest gorilla and run the other way quickly.