The same well-calibrated glass is best for both white and red wines.
DISCIPLES OF THE GRAPE ARE SELDOM without a glass. But which one? Generations of gourmets have debated the optimum form and size of a wine glass. In France, the Institut National des Appellations d’Origine (INAO) has mandated use of a glass recognized by the International Standards Organization (ISO) whose bowl is about twice as high as it is wide. Is it really the best? Because German tasters recommended a rounder glass, Ulrich Fischer, of the Oenology Department at the University of Neustadt, and his colleague Britta Loewe-Stanienda decided to explore the intensity of perceptions of aromas in glasses of various shapes and sizes.
Standards organizations such as the ISO and INAO have stepped in to regulate glassware without having first determined the exact effects of form and shape on perception. It is for reasons of habit, not science, that red wine is served in glasses that are more voluminous than those used for white wine, and mellow wines are served in glasses whose opening is larger than those meant for dry wines.
Calculated Evaporation
Before studying the shape of glasses, the Neustadt researchers sought to determine the physicochemical effects of pouring wine into a glass on the perception of aromas. As a matter of physics we know that the vapor pressure of a molecule dissolved in a liquid depends on the solvent, the solution, and the temperature. We also know that molecules that have passed into the gaseous phase in a glass diffuse into the surrounding air at a rate that depends on the diameter of the rim. On smelling the air in the bowl one inhales these volatile gaseous phase molecules. But many connoisseurs inhale several times in rapid succession. Does another wave of odorant molecules have enough time to pass into the gaseous phase between inhalations? To find out, the researchers used gas chromatography to analyze the air that lies above the wine at different heights and at different times after the wine has been poured into a glass. Some forty compounds were studied at different temperatures.
It was known, too, that the rate of release of the odorant molecules depends on their chemical constitution. Other differences appeared as well: The release rate of esters varied much less, as a function of temperature, than the rate of release of alcohols and volatile phenols. This phenomenon explains why the esters in wines that are consumed when they are cool are concentrated more rapidly than the alcohol, stimulating the perception of fruitiness. Does it also tell us why white wines are drunk at cooler temperatures than red wines? Fruity esters, which often dominate the bouquet of white wines, rapidly present themselves to the nose at low temperatures in sufficient quantities to be perceived, whereas red wines must be served at warmer temperatures for the effects of their volatile phenols to be registered.
Measurements indicated that gourmets are well advised not to quaff their wine at intervals of less than fifteen seconds if they want to have comparable sensations. Their impressions will be strongest if they sniff the air nearest to the rim of the glass.
Tests of Glasses
Having specified the conditions for tasting in detail, the Neustadt researchers tested ten glasses with different maximum diameters, heights, and diameters at the rim. Tasters were instructed to note the intensity of some ten notes (buttery, floral, red fruits, and so on) for the same wine in each glass.
These experiments yielded a great deal of information. With white wines, for example, a narrow bowl brought out the reduced aroma (a faintly vegetal odor suggestive of cabbage) and sulfur character of the wines more than the calix of the ISO glass. Glasses with a large bowl of small or medium height produced weaker sensations than ones with narrow bowls, whatever their height. Although increasing the volume of the bowl did not reduce the intensity of perceptions, glasses with a larger bowl and rim (which are reputed to be particularly well suited for the tasting of red wines) are not superior to the ISO glass, which has a relatively narrow bowl.
Three discoveries in particular upset conventional oenological wisdom. First, the intensity of all perceptions was found to change with the type of glass. Second, increasing the height of the bowl and the ratio between the diameter of the rim and the maximum diameter of the bowl intensified all perceptions. Finally, and contrary to what many manufacturers have claimed, the glass that gave the best results in white wine tastings—the ISO glass—was also the best for red wines. A dogma is slain.