|Temperature and Sparkling Wine||
Temperature affects wine in many ways and at many stages of production. At this time of year, as the days are getting shorter and growing colder the thought of chilling bubbly occupies my mind. How does temperature affect champagne? This is a great question about a wine that is to be served chilled. The extensive variety and style of champagne buckets that have been made over the years bare testament to the crucial role of temperature in serving champagne. First, though, it is important to think a little bit about temperature and what it tells us.
Temperature in a non-technical way is the sensation of warmth or cold. However, in a more technical way, temperature refers to the measure of the heat content of a system based on a standard reference point. For example, 32 ° F represents the temperature at which water freezes at normal atmospheric pressure. But what does this really mean? Temperature gives a measure of the amount of heat in a system. This heat comes from the motion of molecules moving around and bumping into each other. As the temperature is increased molecules move around faster and faster, colliding with each other. Each collision releases energy. This thermal energy is measurable and detectable. Think of when you place your hand in very hot water. The heat you feel comes from the molecules of water moving very quickly and colliding with the molecules in your hand, releasing energy.
Why is thermal energy in your champagne important? Thermal energy does more than move molecules around. Thermal energy plays a significant role in the making and breaking of chemical bonds. It takes energy to form and break chemical bonds. The higher the heat the faster a chemical reaction will go. Also solids dissolve more quickly as the temperature is increased. Aromatic compounds escape from liquid more quickly when it is warm because these volatile compounds have a tendency to escape from liquid and do so more rapidly as they are bounced and jostled around by the faster moving molecules in warmer liquid. Gases also dissolve in liquid at lower temperature. A very important gas for champagne is carbon dioxide from the fermentation process, which dissolves into wine as carbonic acid at cool temperatures and under pressure. More on this later. The fascinating subject of the effect of temperature on grape ripening will be covered in a different article. This article will examine the important effects of temperature on champagne from the point of harvest on.
Much of the white wine in champagne actually comes from the white juice pressed from the black berries of Pinot Noir and Pinot Meunier. Careful pressing with gentle but increasing pressure on the grapes extracts the white juice, which is immediately removed from the skins. The longer the juice stays in contact with the dark skins the more of the undesirable flavenoid phenolics and dark pigments will be extracted. Temperature at the time of pressing plays an important role in dictating the amount of undesirable compounds that are extracted from the grapes. High temperatures at the press will extract more of the phenolics and degrade fruit quality. The highest quality wine comes from whole unbroken clusters that are pressed in small quantities with low pressure at lower temperatures. The yield of juice is lower though making this the most expensive wine.
Wine in many ways is just a complicated mixture of chemicals. Fermentation of juice containing low amounts of solids and at cool temperatures (below 55-60° F) retains the fatty acid esters responsible for a fruity, floral, aromatic nose. Some wine makers will allow the fermentation to take place at higher temperature (65-70° F) to reduce the floral intensity producing a more austere wine. Fermentation is exothermic (generates heat), and must be controlled; if left unchecked in some cases the wine can become too hot driving off desirable aromatics and even stopping fermentation by arresting the yeast.
Heat does have the effect of helping to precipitate proteins from the wine. Heating a wine to 60 C for one day would precipitate nearly 100% of the protein in the wine. However, in the quest to clarify the wine the wine maker must not remove too much protein because it contributes to the retention of carbon dioxide—the bubbles.
The second fermentation in the bottle that adds the bubbles to champagne takes place between 48° F and no greater than 55 F. Some wine makers believe that a low temperature second fermentation increases the amount of carbon dioxide dissolved in the wine. Fermentation at high temperatures causes larger, coarser bubbles. Low fermentation temperature favors the production of lipids that favor bubble retention and produces the more desirable fine beaded bubble.
Part of the unique character of champagne comes from aging surlie—aging the wine in contact with the yeast that performed the second fermentation. At lower temperatures the yeast will release over time amino acids that contribute to the flavor of champagne. Aging surlie at higher temperatures accelerates the release of the amino acids but will compromise the bubble retention and aroma. Some champagnes are aged in cool cellars for years to develop the complexity from agine surlie
An exciting aspect of champagne production is disgorgement or the removal of the yeast plug from the champagne bottle to produce the star bright final product consumers have come to expect. Prior to disgorgement the bottles are chilled to about 4-10° F. Then the neck is plunged into a solution of calcium chloride or glycol solution (5° F) until a plug of ice and debris is formed in the neck of the bottle. The bottle is then briefly opened at a 45° angle to eject the plug, thus clarifying the wine. The wine then receives its dosage of sugar and other elements to finish the wine.
Finally, the temperature regarding the serving of champagne generally is around 40-45° F. Some lower quality wines should be served colder to mask unpleasant flavors. Also, the cooler the wine the more the wine will retain the bubbles. Most sources are in agreement about the serving temperature of champagne. However, the means of chilling the champagne are varied. Some advise against the use of a freezer because they claim it changes the structure of the wine. The rapid cooling appears to mask the flavors of the wine. This needs more research to move this idea from speculation to fact. Most recommend an ice bucket filled with water and ice for 15-20 minutes, placing the bottle in the fridge for several hours. Perhaps, over the holidays I will try to compare some of these techniques.