What is Sherry?

Sherry is broadly defined as a fortified wine subjected to controlled oxidation to create a distinctive flavor.  More specifically, the special oxidized character of sherries are often describe as baked, nutty, and caramelized.  Since the flavors of sherry are derived from complex organic compounds including acetaldehyde, phenyl ethanol, esters, and wood extractives, the aroma and flavor of the original relatively neutral flavored grape variety vanishes during production.

The Andalucía region of southwest Spain has been making Sherry wines for nearly two millennia from the non-descript white Palomino grape.  While the Spanish produce a variety of sherry products, there are essentially two basic types of sherry.  Fino sherries derive their light-straw color and hazelnut, light oaky aromas and flavors from flor yeast fermentation.  Conversely, Olorosos sherries are darker, more amber in color, generally sweeter and are produced in an oxygen rich environment without flor yeast.

​​American Sherry-style

American sherry wines usually fall between the color and aroma extremes between fino and olorosos ranging from light yellow to medium brown in color.  Sugar content of most American sherries range from 1.0-2.5% for dry, to 2.5-4.0% for standard and up to 10% for cream sherry.  Since Palomino is not a widely grown in American vineyard (213 acres in California in 2014), domestic sherry wines are produced from an assortment of mostly white grape varieties.  In the west, in addition to Palomino, Mission, Grenache, Orange Muscat, and French Colombard are used while in the east, Chambourcin, Niagara, Delaware, Muscadine, and Orange Muscat are favored varieties for sherry production.

​​How American Sherry-style is Made

Grapes are normally picked at 22-24 degrees Brix, then crushed and pressed, or pressed immediately on arrival at the winery minimizing skin contact.  Free-run or light pressed juice is often used to make Fino-style sherries while the juice from further pressing usually creates the Olorosos-style sherries.  The pressed juice called “shermat” is then fermented to dryness (no measurable residual sugar to make the white base wine.  The new base wine racked off the lees, and fortified with grape brandy or wine spirits.

Following fermentation, sherry winemakers must make a crucial stylist decision - whether or not to oxidize the base wine with or without yeast. This decision determines the final sherry style; Fino or Olorosos.

​​Yeast oxidation involves the inoculation of base wine with a special yeast strain called flor.  “Flower” in Spanish, flor yeasts produce what looks like thousands of tiny white flowers piled on the surface of the wine.  The base wine is fortified to about 15%, which allows the development of a flor yeast film. 

The “surface-film” method of making flor sherry can be time consuming and expensive so some winemakers have adopted a variation called the “submerged culture” technique.  This process most often applied by larger producers involves inoculating 15% alcohol base wine with flor yeast in a stainless-steel tank where air or pure oxygen is continuously bubbled through the wine.  The tank is regularly stirred or agitated to keep the yeast cells suspended and the development of acetaldehyde closely monitored.Acetaldehyde is an organic chemical compound that is the key to the sensory definition of sherry.  Once the base wine has reached the desired acetaldehyde and flor yeast character, the wine is again fortified to 17-19% then racked off the lees.The finished fino-style sherry is then left to age.

Some vintners elect the non-yeast approach and produce Oloroso-style sherries by either long aging in partially filled oak barrels or by “baking” the base wine.  ​Competitively priced American sherries are often produced by the heating the wine in the presence of air at 120 to 140 degrees for 30 to as many as 120 days.

Some sherries improve with age and different styles dictate differing aging schemes from a few months to a few years.  Most vintners age sherries in American oak barrels to gain a stronger aroma and drier taste.  Traditionally, the solera system is used for storage and blending sherry.  This the same technique often used in the fractional blending of port-style wines consisting of stacks of barrels with each row containing a different sherry vintage.  The oldest wine in the bottom tier is drawn for bottling and is replaced with wine from the tier above and so on for usually five or more tiers.  Few true solera systems are found in American sherry wineries.  While fractional blending may still be done, the expense and effort of maintaining the solera is challenging.

Finishing American sherry may involve some blending to adjust sweetness, color and complexity in order to achieve the vintner’s unique stylist objective.  Once the final blend has been achieved, the sherry may undergo a polish filtering, cold-stabilized and finally, bottled.

​  American
​Sherry-style Wine