Wine Tip: Wine Yeasts, Wild and Tame

Editor’s Note: This is an excerpt from author John Hailman’s book The Search for Good Wine which will be available for purchase September 2014 from the University of Mississippi Press. This particular chapter was written on August 10, 1993.
Humans  made and enjoyed wine for thousands  of years without knowing what caused grapes to ferment. Only in the 1Oth century did Frenchman Louis Pasteur discover that it was wild yeasts on the grapes that converted  their sugar to alcohol. Pasteur also found  that if you boil wine it kills the yeasts, thus “pasteurizing” it against further fermentation. Since then we’ve learned a lot about yeasts and how they work, but could stand to learn more.
Yeasts are one of the most underrated elements in :fine wine, probably having as much to do with a wine’s taste and aroma as either the land where the grapes were grown or the barrels they were aged in. If you get the wrong yeast, a wine can be sickeningly foamy, smell funny, or be sweet and fizzy, or it can re-ferment in the bottle and get cloudy and funny-tasting after you take it home.
Yeasts are one-celled, asexual plants. The best yeasts are well-behaved, working feverishly till all grape-sugar is absorbed, then dying. Others are not so cooperative, hanging around after fermentation ends and giving funny tastes and smells to wines. Worst are the yeasts which die too soon, causing a «stuck” fermentation where partly fermented  wine tastes bad and spoils quickly.
In modem winemaking there are two basic types of yeasts: wild and cultured. There is no such thing as “artificial” yeast. The cultured ones are natural, just cultivated to multiply outside their own areas. Most cultured yeasts come from Europe, especially France and Germany. For some reason, the natural yeasts of Europe, like the grapes, seem to make better wines. But like the grapes, once transplanted  to America they make wines in our climates just as good as if not better than in Europe.
For reasons not yet wholly understood, some vineyards in California now produce better
wild yeasts than in the past, and many wineries are experimenting successfully with them. But they are tricky. Different  wild yeasts existing together  can give wines greater complexity, but can also clash. One group of yeasts can predominate in hot, dry years and, another  in cool, wet years, giving wines of very different character. Wild-yeast tastes are seldom consistent  from year to year.
One wine, port, receives a special yeast treatment to soften its natural harshness, being dosed with grape brandy before fermentation ends to kill the yeast before the wine gets too dry. Other wines like chardonnay are often left for months on the expired yeast cells among the “lees” in the bottom of the barrel, which connoisseurs say makes wine creamy, spicy and more complex in flavor.
Cultured yeasts are usually put into a vat of grapes dry, allowing the juice to activate them. Some U.S. wineries use “liquid starter,” yeasts already multiplying in small amounts  of wine. These so-called “hot” starts are less often “stuck,” but old-timers say the faster you ferment a white wine, the less sublet it is, so cooling tanks are used to slow white-wine fermentations. For reds, on the other hand, many winemakers claim a warmer fermentation “bums off” unwanted smells, so they are fermented much wanner.
You may soon be reading more wine labels which describe the yeasts used, wether wild or domesticated, with names taken from famous wine-sites like Champagne or Montrachet from France, or Steinberg from Germany. Those words on a wine label are not esoteric wine snobbery, but evidence of a winemaker seeking the cutting edge, trying yet another way to make wines more varied and enjoyable.
John Hailman of Oxford is a regular contributor to HottyToddy.com on two subjects: Law and Wine. Now retired from both his “day job” as a federal prosecutor in Oxford after 33 years and his “night job” of 25 years as a nationally syndicated daily columnist in more than 100 daily papers on wine, food and travel for Gannett News Service and the Washington Post, Hailman will cover both topics under the titles of The Legal Eagle and Wine Tips of the Week. HottyToddy.com will also run periodic excerpts from Hailman’s upcoming book of humorous legal stories, From Midnight to Guntown: True Crime Stories From A Federal Prosecutor in Mississippi. Hailman now teaches Federal Trial Practice and Law and Literature at the University of Mississippi.