Sherry is different from many standard varieties of wine–namely due to the step included in the fermentation process known as fortification. The steps behind fermenting and fortifying sherry are necessary to produce this wine according to its traditional standards, and result in a strong, complex and flavorful beverage when properly accomplished. Sherry is not the only type of fortified wine. Other varieties of fortified wine include port (or Porto) and Madeira wines, which come from Portugal rather than the Jerez region of Spain that produces sherry.
Beginnings of the Sherry Fermentation Process
The fermentation of sherry begins with the harvest of sherry grape varietals–predominantly fino, but also moscatel and Pedro Ximenez grapes. It takes about 20 days to harvest the ripe grapes, and the best grapes go to the presses to be crushed into juice once stems and leaves have been removed.
The crushed grapes used in winemaking are referred to as must. In the production of sherry, several musts are used, and the first is referred to as mosto de yema. The first must is fermented into sherry wine, the second is used for sherry vinegar and the third is used to produced distilled wine.
Next Steps of Sherry Fermentation: The Crianza Process
The “crianza” process is an element of Jerez winemaking that is unique to the production of sherry. The juice from the first must will be stored in stainless steel vats in cellars and allowed to naturally ferment for several months. Harvest season is typically in late August and early September, and fermentation will usually end in January.
Once January comes around, the solids that are present in the first must–mostly grape skin and seed fragments–will have fallen to the bottom of the vat, where they’re kept separate from the fermented wine. The wine in its present state will be sampled as-is and then poured into casks based on taste and potential. The best wine will be used for finos and manzanillas and fortified accordingly, fuller-bodied wine will be more heavily fortified to produce oloroso sherry and poor-quality wine will be set aside to be distilled or used in vinegar.
Fortification of Traditional Sherry
Based on the intended type of sherry made from the soil and grapes of the Jerez district, the freshly fermented wine will be fortified to several degrees.
• Wine that will be used for Fino and Manzanilla sherry will have distilled, high-alcohol wine added to increase the alcohol content from 11 to 12 percent alcohol by volume (ABV) to 15 or 15.5 percent ABV.
• To make Oloroso sherry, extra alcohol is added and the finished product will stand at anywhere from 17 to 22 percent ABV.
In both instances, the distilled wine is first added to older sherry and mixed. The resulting mixture is added to younger sherry to balance it properly.