Yeast and Fermentation Session
Alex Gertsman, Flottweg, Independence, KY, USA
ABSTRACT: Kvass is a traditional Russian malt beverage, typically either non-alcoholic or slightly alcoholic (1–1.5%). Traditional homemade kvass uses rye bread as the primary raw material. In some recipes the rye bread is roasted, and its croutons are then actually used for making wort. After the wort is prepared and other ingredients, such as sugar, honey, raisins, and spices, are added depending on the recipe, the product is cooled off and undergoes a quick fermentation. In the old days of kvass making spontaneous fermentation was used and then replaced by use of baker’s yeast. The fermentation process with baker’s yeast usually would take place from 6 hr to 1–1.5 days, after which the product was cooled and was ready for consumption in about another day. Kvass brewers who wanted an extra kick from this great summer beverage and desired to have fewer off-flavors caused by baker’s yeast strains, use of brewers’ yeast became an alternative. Finding the right yeast became a challenge since the wort is not quite stable, being unhopped, and not suitable for the longer term fermentation that is carried out with beers. Naturally first choices were the English ale yeast strains, known for their shorter fermentation time and also of the same Saccharomyces cerevisiae species as baker’s yeast. Differences include enrichment of brewer’s yeast with essential minerals and B vitamins, but the real difference in strain characters is the ability of brewer’s yeast to tolerate higher alcohol concentrations and its tendency to produce fewer off-flavors, but all at the expense of longer fermentation time than brewer’s yeast. The big challenge is to obtain the desired attenuation while working with brewer’s yeasts. It was empirically determined that some of the Saccharomyces cerevisiae strains could be pitched at temperatures of about 90–93°F as the wort being cooled underwent top fermentation at room temperature for 1.5–2 days; afterward green kvass was placed in a refrigerator and underwent further fermentation under cool temperatures for another day. The settled yeast was decanted, and another day of maturation in the refrigerator produced a very good flavored beverage with an alcohol content of 2.5–3% by volume.
Alexander Gertsman received a B.S. degree in chemical engineering from New Mexico State University. He has been working with centrifuges for 16 years, including employment with Alfa Laval and currently Flottweg, both in North America. Alexander has been responsible for brewery applications and sales for Flottweg in North America since 2005. He is also a profound crafter of homemade kvass, a Russian national malt beverage.