King of the Yeasts

By Brian Charles Clark
Washington State University
wine.wsu.edu

Where does a great glass of wine get its start? In the vineyard, certainly, as the foundation for good wine is always good fruit. But once the fruit is picked and turned over to the winemaker, yeast can make or break a great wine.

Once yeast is added to grape must (the juice and, if red, skins of the grapes), winemakers hope it performs as expected. Ideally, yeast should perform consistently batch after batch, regularly metabolizing a certain amount of sugar into ethanol. A yeast that underperforms may result in a sluggish or “stuck” fermentation—an expensive, stinky disaster for a commercial winery and a disheartening mess for a home winemaker.

Especially with winemakers encouraging growers to leave the grapes on the vine a bit longer in order to increase the Brix or sugar content of the ripe fruit, a well-behaved yeast is a must-have tool in the vintner’s kit. Increased hang time results in bigger, bolder wines, but the increased sugars in the fruit can stress yeast that doesn’t have the proper nutritional backbone to handle the job.

Partnering with the commercial yeast producer Lallemand, WSU food scientist Charlie Edwards and his colleagues formulated strains of yeast that can stand up to high-sugar grape musts. Released commercially about a year ago, these new Lallemand yeasts, Edwards said, “are better acclimated to a grape must” with lots of sugar.

A yeast with a poor nutritional profile—one that, for instance, gobbles up as much sugar as it can in the first few days of fermentation—results in wine with more hydrogen sulfide, giving the finished product a sulfury, rotten-egg smell.

Lallemand is now marketing internationally its yeasts based on WSU research, Edwards said. Each package proudly bears a slug of text saying the yeast was “developed in collaboration with Washington State University.”

Although the precise formulation of Lallemand’s yeasts is a trade secret, Edwards said the difference is in the process of manufacture. “We looked carefully at a large number of products under commercial winemaking conditions,” Edwards said before zeroing in on strains that performed consistently and had a nutritional profile suitable for the flavorful wines so esteemed by today’s consumers.