In recent years, more and more winemakers are looking to the original winemaking process to further enhance the quality of their wines. For example, some winemakers have chosen to return to the tradition of picking whole bunches of grapes back without destemming them, allowing the grapes to ferment with the stems, or fermentation with stems, also known as whole bunch fermentation.Whole bunch fermentation is the most primitive method of making red wine. Before the invention of destemming machines in the 20th century, almost all red wines were made using the stalk fermentation method. The wines made during that period were generally more brutal in tannin, especially when the stems were not fully ripe. Nowadays, most red grapes are destemmed before fermentation, but the technique of fermentation with stems can still be used to adjust the style of a wine, and is often used to make Pinot Noir and Syrah wines. This method is used by a number of well-known wineries in Burgundy, such as Domaine de la Romanee-Conti (DRC), Domaine Leroy and Domaine Dujac, to create unique wines from the grapes. Fermentation with stems can affect the aroma, texture and tannin structure of a wine. The use of fully ripe stems not only avoids harsh tannins and abrupt raw green flavors in the wine, but also gives the wine fresh flavors of flowers, herbs and spices. The involvement of the stems in the fermentation process lowers the temperature in the fermenter and makes it more stable, which in turn allows for a gentler extraction of tannins and flavors, resulting in a more refined, fresher wine. The stems also contain phenolic compounds that enhance the tannic structure of the wine. Fermentation with stems also reduces the alcohol content of the wine. The stems contain a lot of water rather than sugar, which does not convert more sugar into alcohol during fermentation, and because whole bunches are usually fermented in open vessels, some of the alcohol evaporates during the fermentation process, which relatively reduces the alcohol content of the wine. In addition, the potassium contained in the stems can combine with the tartaric acid in the wine and form a precipitate, thus reducing the overall acidity of the wine. The stems also absorb some of the pigments in the wine during fermentation, giving the finished wine a lighter, more translucent color. Stemmed fermentation can be done by leaving all the grapes on their stems, by placing some of the grapes in bunches in fermenters with destemmed grapes, or by destemming and crushing all the grapes and then adding some of the stems to the fermentation. During the fermentation with stems, some whole bunches may be deposited by gravity to the bottom of the fermenter and start the in-fruit fermentation due to lack of oxygen. This is somewhat similar to carbonic maceration, but it is not the same. In CO2 maceration, whole bunches of uncrushed grapes are put into the fermenter and then the fermenter is filled with CO2 and sealed, whereas in stemmed fermentation, the fermenter is not sealed. Whole Bunch Pressing is used in white wine making, where the whole bunches are pressed directly into the press after harvesting, with the presence of the stems helping to create gaps between the grapes and allowing the juice to drain more easily. Compared to the common method of “destemming first, then pressing”, whole bunch pressing shortens the time the juice is in contact with the skins, thus reducing the extraction of color and phenolics, resulting in clearer juice and a more refined and elegant style of wine.
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